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Speaker 1: Katie, if you want to learn more about some creature

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Speaker 1: you're planning to feature, what's a good way to get started? Well,

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Speaker 1: I use this obscure technology called Google, or I could

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Speaker 1: find one and observe it. That's it. You just read

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Speaker 1: about it or observe it. You don't like poke it

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Speaker 1: or anything. I mean, in general, I think in the

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Speaker 1: field of evolutionary biology, they discourage poking wild animals. Yes.

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Speaker 1: Does that mean therefore that you also, like, never smashed

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Speaker 1: two of them together at high speeds? Pretty strongly discouraged. Interesting?

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Speaker 1: I mean, in my experience, that's a pretty good way

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Speaker 1: to learn what something's made out of. I think that

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Speaker 1: someone needs to find some advocacy organization or pro bono

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Speaker 1: lawyers to represent the protons you guys have been smashing. Oh,

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Speaker 1: we are facing the biggest class action lawsuit in history. Hi,

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Speaker 1: I'm Daniel. I'm a particle physicist and a professor at

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Speaker 1: UC Irvine, and I am not prepared for a lawsuit

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Speaker 1: from ten to the thirty protons. Hi. I am Katie Golden.

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Speaker 1: I host the podcast Creature Feature, and I am boning

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Speaker 1: up on my lawyerism to try to sue the pants

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Speaker 1: and particles off of Daniel, how are you going to

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Speaker 1: manage all of those clients? I mean, what if they

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Speaker 1: disagree about how much money to ask for or you know,

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Speaker 1: whether to send me to prison or something. I mean,

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Speaker 1: tended the thirty clients is a lot to wrangle. I mean,

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Speaker 1: I think I'll just send out a general mailer or

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Speaker 1: do an ad on TV. That's like, if you're a particle,

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Speaker 1: and you are a loved particle were involved in a

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Speaker 1: smashing well, I hope that all the protons out there

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Speaker 1: are not mad at us for all the times we've

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Speaker 1: been smashing them together to try to learn about the

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Speaker 1: nature of the universe. And Welcome to the podcast Daniel

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Speaker 1: and Jorge Explain the Universe, a production of I Heart

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Speaker 1: Radio in which we do encourage people to smash stuff

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Speaker 1: together in order to learn about how the universe is

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Speaker 1: put together. We try to ask and answer some of

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Speaker 1: the deepest questions about the very nature of the universe,

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Speaker 1: the fundamental fabric of reality. What in the end is

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Speaker 1: the universe made out of our space and time, fundamental

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Speaker 1: our particles, the basic building blocks of the universe, Or

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Speaker 1: is it something even weirder, even deeper, even stranger than

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Speaker 1: our little minds can suppose, and we don't just smash

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Speaker 1: particles together. We look out into space to see other

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Speaker 1: things that Mother Nature or Grandpa Universe has smashed together

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Speaker 1: on our behalf, so that we can ask huge questions

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Speaker 1: about how those things are put together. The moral of

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Speaker 1: the story is smash stuff, learn a lot, but of course,

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Speaker 1: watch out for people's rights and be careful about applying

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Speaker 1: this to wild animals. My co host and friend Jorge

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Speaker 1: can't be here today. He is traveling through Spain and Portugal,

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Speaker 1: so we are delighted to have our regular co host,

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Speaker 1: Katie Golden. Katie, thanks very much for joining us. Yeah,

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Speaker 1: of course, I think it is a little bit suspicious

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Speaker 1: that Jorge is missing when we are talking about smashing

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Speaker 1: things together to learn more about them. But okay, and

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Speaker 1: you know, astronomers are always delighted when stuff smashes into

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Speaker 1: other stuff in outer space. They're not capable of building

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Speaker 1: a collider like we can. You know, we can smash

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Speaker 1: protons together to learn about what's inside of them, but

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Speaker 1: astronomers can't build a black hole collider for example. Yes,

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Speaker 1: they got dreams, they got plans, but sometimes they get

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Speaker 1: lucky anyway, and the stuff just sort of happens out

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Speaker 1: there in the universe for them to watch, and they

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Speaker 1: don't have to worry about the black holes rights or

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Speaker 1: it's legal fees or or whether he gets mad because

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Speaker 1: they're just taking notes. And I wonder, Katie, if the

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Speaker 1: same thing happens for you. I mean, sometimes I watch

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Speaker 1: these nature shows about like giraffe battling by slamming their

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Speaker 1: next together, or you know, big horn rams being in

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Speaker 1: themselves together. You guys also learn a lot, don't you

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Speaker 1: when animals smash themselves together. Yeah, I mean, to be fair,

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Speaker 1: I am not currently doing research, but when I was

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Speaker 1: a little undergrad, I was definitely involved in some of

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Speaker 1: these research projects. And one of them was just going

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Speaker 1: out and watching squirrels and taking notes, and it made

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Speaker 1: us very popular among the school body, just sitting there

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Speaker 1: being the squirrel people, watching the squirrels, writing down what

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Speaker 1: the squirrels were doing. But yes, observing wildlife, observing animals

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Speaker 1: is extremely instructive for revolutionary biologists. It can be very

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Speaker 1: difficult because, of course, when you're observing things in nature,

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Speaker 1: it is not a laboratory environment, so you know, eliminating

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Speaker 1: the variables that are inevitable when you have sort of

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Speaker 1: this chaotic natural environment can pose a kind of tricky

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Speaker 1: thing for research, But yeah, it is. It is a

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Speaker 1: hugely important side of evolutionary biology is just looking at

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Speaker 1: what an animal is doing and hoping it doesn't notice

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Speaker 1: you looking at it. All right, But I want to

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Speaker 1: clear answer here. Do squirrels smash themselves together or not?

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Speaker 1: They smash acorns into their little faces, but they don't

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Speaker 1: smash acorns against each other's no, like squirrel acorn Collision

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Speaker 1: research program, not exactly. They may smash it into the

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Speaker 1: ground a little bit to get that buried in there,

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Speaker 1: but they don't have a squirrel acorn hadron collider quite yet. Well,

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Speaker 1: you know, there's just a limitation to how much you

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Speaker 1: can learn by observing stuff. We were just looking at protons,

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Speaker 1: for example, we never would have understood what was inside

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Speaker 1: them and seeing this incredible dance of the corks and

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Speaker 1: the gluons that are all tied together to make this

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Speaker 1: crazy thing we call a proton. And so it's these

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Speaker 1: dramatic events when protons smashed together or when larger objects

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Speaker 1: smashed together. Squirrels black holes for example, a list nobody

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Speaker 1: has ever made before in the history of time that

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Speaker 1: consists only of squirrels and black holes seems pretty complete

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Speaker 1: to me. What else could there be onside a list?

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Speaker 1: But when these things do happen, you have an incredible

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Speaker 1: opportunity to learn something about the nature of what's inside

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Speaker 1: these objects. I mean, we know something about what's inside squirrels,

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Speaker 1: but we have deep questions about what's at the heart

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Speaker 1: of neutron stars, what's inside black holes? Hey, what's going

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Speaker 1: on even inside normal stars? Stars like our sun have

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Speaker 1: incredible convection zones of plasma slurping and slashing and making

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Speaker 1: magnetic fields that flip every eleven years, we still don't

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Speaker 1: even understand what's going on inside a normal star. To

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Speaker 1: be fair, if you want to know what's going inside

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Speaker 1: of a squirrel, you can't really do that just by

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Speaker 1: watching the squirrel. Uh. It involves the process that I

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Speaker 1: may not want to describe to people right now, but

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Speaker 1: I imagine it is quite difficult to know in a

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Speaker 1: similar way what is going on inside something like a

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Speaker 1: star when you can only look at it and not

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Speaker 1: dissect it on a table. Yeah, and even star collisions

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Speaker 1: are pretty rare, But astronomers are lucky that there's another

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Speaker 1: way to see inside of stars. You don't have to

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Speaker 1: smash them together. Sometimes they just blow up on their own.

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Speaker 1: They erupt and deposit all of their innerds now on

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Speaker 1: their outers, so that we can study them and see

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Speaker 1: what was inside that star, just like squirrels, just like

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Speaker 1: got to one too many acorns, right exactly, I'm stuffed.

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Speaker 1: And when stars do go boom, it's an incredible opportunity

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Speaker 1: to learn about the processes that are going on inside

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Speaker 1: the star, why they suddenly got imbalanced. Plus it's a

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Speaker 1: pretty dramatic light show. Now you say that, but I

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Speaker 1: have never gotten to see a star explode, and I

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Speaker 1: would really like to. So where can I sign up? Well,

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Speaker 1: one problem is that we don't even really understand why

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Speaker 1: it happens and when it happens. We don't have a

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Speaker 1: scientific model that can predict when a given star is

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Speaker 1: going to go supernova. So all we can do is

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Speaker 1: scan the night sky. And you know, to me, that's

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Speaker 1: fascinating because the night sky seems pretty stable. If you

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Speaker 1: like looking at the stars, you probably are looking at

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Speaker 1: the same stars that looked pretty much the same as

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Speaker 1: your parents did, and your grandparents and their ancestors did.

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Speaker 1: The night sky does not change very much, but when

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Speaker 1: it does, when that happens, when a supernova goes boom,

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Speaker 1: it's very dramatic. These things can be as bright as

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Speaker 1: an entire galaxy, so it's a pretty exciting event when

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Speaker 1: it does happen. But you know, you're right, it's not

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Speaker 1: something that we've been able to see very recently, and

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Speaker 1: even though supernovas are expected to be rare, something of

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Speaker 1: a mystery about why we haven't seen more supernovas. In fact,

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Speaker 1: it's been over four hundred years since we have seen

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Speaker 1: a supernova in our galaxy. It seems strange to me

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Speaker 1: because even if it's rare, it seems like there's so

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Speaker 1: much stuff in the galaxy that you would at you know,

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Speaker 1: you are increasing your odds. Like when they say an

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Speaker 1: infinite number of monkeys on an infinite number of typewriters.

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Speaker 1: It's like an infinite maybe not infinite, but many many

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Speaker 1: exploding monkeys who once in a while explode. You would

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Speaker 1: think you'd catch a monkey explode. I'm so sorry to

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Speaker 1: everybody out there who just had the mental image of

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Speaker 1: an exploding monkey put into their head. I hope that's

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Speaker 1: a positive addition to your day. Whatever else is going on,

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Speaker 1: which we don't condone. We do not condone it. We

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Speaker 1: simply describe it exactly scientifically. We're just observing super monkey nova's.

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Speaker 1: You know, it's not our fault. We're just you know,

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Speaker 1: doing our best to learn something from it. So that's

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Speaker 1: exactly what we're gonna be talking about today. The title

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Speaker 1: of today's AT episode is why haven't we seen a

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Speaker 1: Milky Way supernova in more than four hundred years? Have

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Speaker 1: we just not looked up? Like, has anyone you know,

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Speaker 1: just kind of checked it out? You mean, have we

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Speaker 1: been so self involved for the last four hundred years

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Speaker 1: that we haven't noticed incredible explosions in our sky? Right?

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Speaker 1: It's these kids with their noses and their smartphones all

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Speaker 1: the time. They just don't notice them. Well, I think

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Speaker 1: that the last person to see a supernova in the

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Speaker 1: Milky Way was Kepler, himself, famous man of astronomy, of course,

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Speaker 1: and I'm pretty sure that he didn't have a smartphone,

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Speaker 1: and that in most of the intervening four hundred years,

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Speaker 1: astronomers have not been distracted by their smartphones. So that's

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Speaker 1: a good idea. But I think we're gonna have to

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Speaker 1: look for other explanations for why we haven't seen any

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Speaker 1: supernovas from the Milky Way in our sky in four

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Speaker 1: hundred years. It's something of a cosmic mystery that we're

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Speaker 1: going to dig into today, but before we do, we

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Speaker 1: were wondering what our listeners thought about this question. People

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Speaker 1: understand why there hasn't been a supernova in our galaxy

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Speaker 1: that we've spotted in several hundred years. So thanks very

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Speaker 1: much to everybody who volunteered to answer random questions. They

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Speaker 1: heard this question without any chance to prepare, and we

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Speaker 1: asked them to just speak from the top of their head,

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Speaker 1: so we get a sense for what you, dear listener,

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Speaker 1: are thinking about as you listen to this podcast episode.

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Speaker 1: What you know, what you don't know? What the ideas

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Speaker 1: are out there. If you'd like to hear your voice

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Speaker 1: speculating on the podcast for a future episode, please write

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Speaker 1: to us. We'd love to have you on the show.

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Speaker 1: Just drop us an email to questions at Daniel and

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Speaker 1: Jorge dot com. Here's what our listeners had to say.

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Speaker 1: If I remember rightly, there are a couple hundred billion

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Speaker 1: stars in the Milky Way, and supernovas are made from

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Speaker 1: stars that last much shorter than ours. So if they

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Speaker 1: were all eligible, there the right kind to be a

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Speaker 1: super nova and being produced at a constant right throughout

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Speaker 1: the life of the universe, we'd be seeing about one

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Speaker 1: every two and a half years, if I've done my

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Speaker 1: math right. Since we haven't seen one in at least

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Speaker 1: four hundred years, which is about a hundred and sixty

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Speaker 1: times as long as expected, my guess is that only

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Speaker 1: about one in a hundred and sixty stars is the

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Speaker 1: right kind to end up as a supernova. I've actually

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Speaker 1: thought about this question a couple of times, because, like

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Speaker 1: most people, I would love to see a supernova in

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Speaker 1: broad daily. I keep asking beetle juice, but it doesn't listen.

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Speaker 1: So I think that in individual galaxies they are just

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Speaker 1: a rare event. Um, there's only so many stars in

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Speaker 1: a galaxy, so I think they're pretty rare on a

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Speaker 1: galaxy scale, but on a universal scale, because there's countless galaxies,

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Speaker 1: they become common events. So that's my guess. Years is

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Speaker 1: like a blink of an eye in the galactic time scales.

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Speaker 1: So I think we just haven't seen a supernova in

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Speaker 1: our Milky Way yet. We haven't seen a Milky Way

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Speaker 1: supernova in more than four hundred years, because supernova are

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Speaker 1: not just that frequent. Quite a bit of the Milky

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Speaker 1: Way galaxy is hi didn't behind various gas clouds and

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Speaker 1: the central budge, so we don't see what's happening on

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Speaker 1: the other side of the lisk. But what is the

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Speaker 1: rate of supernova occurrence? I have no idea. I think

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Speaker 1: the answer to this is that there's probably a statistical

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Speaker 1: anomally that if the Sun has been around for five

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Speaker 1: billion years and there's like a billion stars in our

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Speaker 1: galaxy or a couple of billion stars in the galaxy,

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Speaker 1: and that not every star turns into a supernova, you

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Speaker 1: might just seduce the statistics suggests that one might not

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Speaker 1: have during this time, that one might happen in a

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Speaker 1: reasonable period of time. But four under views is not

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Speaker 1: a reasonable period of time in terms of the galaxy.

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Speaker 1: This question reminds me of the question that I asked

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Speaker 1: my grandmother when she was trying to tell me about

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Speaker 1: God and angels and all that good stuff. And I

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Speaker 1: would ask her, but Grandma, why can't we see angels?

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Speaker 1: Why can't we see these things that you're talking about

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Speaker 1: that used to be a long time ago? And she

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Speaker 1: was telling me that the reason is that people are bad,

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Speaker 1: not the people used to be good before then, and

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Speaker 1: that's why we could see all that stuff. Now we

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Speaker 1: are bad and they won't. We cannot see them anymore.

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Speaker 1: They won't appear before our eyes. So with the milk,

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Speaker 1: keep with supernova. Could say, also, it's a combination of

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Speaker 1: dus distance and dumb luck that we cannot see them,

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Speaker 1: but also might be because we are bad. I love

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Speaker 1: the idea that we've just been too naughty to see

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Speaker 1: a supernova. This is our punishment. It's like some kind

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Speaker 1: of galactic council has like, oh, humans destroying your environment, naughty, naughty,

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Speaker 1: no supernovas for you. I know, like we don't deserve

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Speaker 1: a supernova. You know, we haven't earned it. It's for

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Speaker 1: like the good aliens, not for us. Right, we got

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Speaker 1: to clean our rooms and rainforests before we get a supernova. Yeah, exactly.

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Speaker 1: I like the idea that the universe is judging us.

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Speaker 1: But I think that the rest of the listener has

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Speaker 1: really put their finger on sort of the spectrum of

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Speaker 1: ideas here. You know, it's true that we haven't seen

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Speaker 1: one in four hundred years, but is that unexpected? Do

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Speaker 1: we think we should have seen one in four hundred years,

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Speaker 1: because it's true that four years feels like a long

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Speaker 1: time to us humans, but it's just a blink on

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Speaker 1: cosmic iron scales or processes play out over millions and

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Speaker 1: billions of years. So it's a fair question whether or

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Speaker 1: not we should have expected to see one, right, because

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Speaker 1: like if you're you know, if you live in England,

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Speaker 1: you expect to see rain all the time, but if

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Speaker 1: you live in Southern California you never see rain ever,

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Speaker 1: So the different environments between Southern California and England, you

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Speaker 1: will have kind of a different expectation for these phenomenon. So,

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Speaker 1: you know, when we don't see stuff in the Milky Way,

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Speaker 1: I guess I'm asking is the Milky Way like, should

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Speaker 1: it be exploding all the time? Is it more of

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Speaker 1: a southern California? What is the weather of the Milky Way? Well,

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Speaker 1: you know, meteorologists are famously bad at predicting supernovas. You know,

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Speaker 1: they say they're going to come on Tuesday afternoon and

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Speaker 1: then boom Wednesday afternoon. When you make your picnic, that's

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Speaker 1: when all the supernovas come. And I'm always dressed the

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Speaker 1: wrong way. What is your supernova outfit look like Katie.

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Speaker 1: It's very shiny, lots of lots of frills and shoulder pads.

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Speaker 1: Of course, well, I think you put your finger on

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Speaker 1: the question, and so we are going to talk about

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Speaker 1: that today. How often we expect to see supernovas in

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Speaker 1: our galaxy and then ideas for why we are not

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Speaker 1: seeing as many as we expect. But first maybe we

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Speaker 1: should talk about the basics, for example, like what is

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Speaker 1: a supernova, how does it work, what do we know

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Speaker 1: about it? And why is it even possible to see

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Speaker 1: one from so far away? I mean from the name,

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Speaker 1: it sounds like it's a nova, but really big and

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Speaker 1: super they are in fact the nova and nova is

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Speaker 1: a Latin word that means new, and so the name

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Speaker 1: supernova actually comes from another famous man of astronomy, Tico

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Speaker 1: bra Hey, who observed one in the fifteen hundreds, and

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Speaker 1: he wrote a book about them, whose title is in

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Speaker 1: Latin but includes the words nova and stella as in

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Speaker 1: new star. And the word nova was later used to

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Speaker 1: describe new things in the sky, including supernova super new

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Speaker 1: things in the sky. That's really interesting because I think

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Speaker 1: of a star exploding is kind of like the death

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Speaker 1: of a star, the violent death of a star. But yeah,

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Speaker 1: nova being like it's something new, some kind of new thing,

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Speaker 1: is I guess a nicer way to think about it. Yeah. Well,

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Speaker 1: often these things that are blowing up are in other galaxies,

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Speaker 1: really far away things that we couldn't see. The star

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Speaker 1: that exploded was individually way too dim for us to

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Speaker 1: see with the naked eye. But once it becomes a supernova,

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Speaker 1: it can outshine the entire galaxy that is in becoming

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Speaker 1: visible and bright in the sky. So you're right that

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Speaker 1: when a star goes supernova, it's at the end of

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Speaker 1: its life, so it's not really new. It's new to

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Speaker 1: us because it went from totally invisible in the sky,

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Speaker 1: one star out of billions in a distant galaxy, to

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Speaker 1: something that is now visible, so it's new in the sky.

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Speaker 1: That's interesting to me that it's so bright, because when

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Speaker 1: I think of something dying, I think of it's sort

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Speaker 1: of fading, you know, like when a light bulb dies,

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Speaker 1: it kind of fades, it flickers out, or when a

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Speaker 1: candle dies, it flickers out. But if it's really bright,

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Speaker 1: if after it dies it explodes and creates something really bright,

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Speaker 1: it sounds like it's releasing a huge amount of energy.

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Speaker 1: It seems counterintuitive to it being a dying star. That's

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Speaker 1: a good point, and it shines a light right on

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Speaker 1: what's going on in the supernova, because supernovas are not

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Speaker 1: like fires that burn gently for a long time and

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Speaker 1: then eventually just sort of flicker out and fade. They're

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Speaker 1: more like a bomb, right where the fuse is going

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Speaker 1: for a long time and then most of the energy

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Speaker 1: is released at the very very end. Right, it's very

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Speaker 1: dramatic sort of ending of the life of an object.

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Speaker 1: And you know, interestingly, the same thing is sort of

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Speaker 1: true of black holes. Black holes evaporate, you leave them

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Speaker 1: out in the middle of space, and they do so

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Speaker 1: by giving off hawking radiation. And the hawking radiation they

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Speaker 1: give off is brighter as the black hole gets small.

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Speaker 1: So as the black hole gives off radiation gets smaller

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Speaker 1: and smaller, it starts to give off more and more radiation.

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Speaker 1: So the last gasp of a black hole would actually

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Speaker 1: be very bright. You would like go off in a

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Speaker 1: bang of glory. That's I love that, that's I'm proud

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Speaker 1: of them, that's good for them. Is that how you

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Speaker 1: want to go out, Katie, You don't want to just

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Speaker 1: podcast to the end, dribbling out a few last words.

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Speaker 1: You want to have like one dramatic podcast at the

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Speaker 1: very end of your career. Exactly. Yeah, if I could

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Speaker 1: go the way a black hole goes, and you know,

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Speaker 1: just like shootout podcast rays everywhere all at once, that'd

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Speaker 1: be great, right, the super podcast nova. Well, in order

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Speaker 1: to understand why supernovas are so bright and so dramatic,

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Speaker 1: we have to think a little bit about what's going

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Speaker 1: on inside them. Now, like everything out there in the universe,

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Speaker 1: it's not something that we understand very well, but we

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Speaker 1: do have something of a reasonable cartoon description of what's

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Speaker 1: going on why supernovas are o dramatic. And remember, the

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Speaker 1: context is how a star works at all, Like why

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Speaker 1: are there stars anyway? You know? Which you have is

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Speaker 1: a huge blob of gas and dust in the universe

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Speaker 1: which gravity has gathered together into a compact, dense object,

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Speaker 1: and squeezing it together makes it hot. And then because

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Speaker 1: it's so hot and so dense, it triggers fusion in

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Speaker 1: the heart of the star. So you squeeze hydrogen together,

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Speaker 1: for example, and you get helium. You get those two

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Speaker 1: protons to overcome their positive charges and to pop together

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Speaker 1: into a new kind of thing. That helium gets fused

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Speaker 1: together into something even heavier. And the cool thing about

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Speaker 1: fusion is that it doesn't just make heavier stuff. It

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Speaker 1: also releases a lot of energy. So gravity pulls this

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Speaker 1: stuff together and then creates the conditions necessary for fusion,

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Speaker 1: which pushes back out. So the energy from fusion, the particles,

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Speaker 1: the photons, pushes back out on the star. And that's

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Speaker 1: why the star can burn for billions of years. That's

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Speaker 1: why you get like a stable, say, situation, like why

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Speaker 1: do stars even happen? Because there's this incredible balance between

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Speaker 1: gravity pushing in on the star, trying to make it

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Speaker 1: into a black hole, and fusion pushing out on the star,

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Speaker 1: basically a bomb blowing the star up. And these two

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Speaker 1: things can stay in balance for billions of years, depending

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Speaker 1: on how massive the star is. But one thing I

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Speaker 1: know about stars, since we have one, and it's called Mr.

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Speaker 1: Sun or Mrs Son, it gives off heat. So this

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Speaker 1: to me seems to indicate that, like, you know, this

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Speaker 1: is not like a self contained system. If I can

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Speaker 1: feel the Sun, feel the warmth from it, and it

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Speaker 1: doesn't that mean it is losing energy at some kind

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Speaker 1: of rate, Like, is it in the same way as

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Speaker 1: like a fire burns fuel, is it running out of

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Speaker 1: fuel as it burns? The star definitely is giving off energy.

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Speaker 1: It's not self contained, so it is using up fuel,

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Speaker 1: and the fuel four fusion are light elements, so mostly hydrogen.

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Speaker 1: Hydrogen is the most plentiful thing in the universe. Most

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Speaker 1: of the universe that's made out of baryonic matter like

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Speaker 1: protons and neutrons and our kind of stuff is hydrogen.

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Speaker 1: So there's no shortage of hydrogen around. And most of

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Speaker 1: the life of a star is burning that hydrogen and

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Speaker 1: turning it into something heavier helium, and then if it's

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Speaker 1: big enough and heavy enough, it can create the conditions

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Speaker 1: to burn that helium into something heavier, and if it's

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Speaker 1: then hot enough to burn the results of that fusion,

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Speaker 1: it can just keep going heavier and heavier and heavier

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Speaker 1: until it gets up about too iron. In each case, though,

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Speaker 1: You're right, it's using up some of the energy stored

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Speaker 1: in those light elements to turn into heavier elements and

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Speaker 1: give up some of that energy, right, So, like where

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Speaker 1: does that energy come from? It comes from the original

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Speaker 1: energy of that hydrogen. You know, you have that hydrogen,

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Speaker 1: it's floating around in the universe. You now squeezed it

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Speaker 1: down to a very compact object a star. It's buzzing around,

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Speaker 1: it's very high temperature. Now you've captured those protons into

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Speaker 1: helium and in doing so, they give up some of

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Speaker 1: that energy, which then gets radiated away into space to

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Speaker 1: make you have a nice summer southern California day. I

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Speaker 1: don't know about nice, but yes, uh, given how hot

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Speaker 1: it has been, thanks Son. So I guess like I'm curious,

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Speaker 1: like when a star dies, is it running out of

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Speaker 1: fuel or is it like collapse and getting too heavy,

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Speaker 1: because it seems like that one of those things would

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Speaker 1: quote unquote kill the star right exactly. It's definitely not

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Speaker 1: running out of fuel. When a star dies and go supernova,

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Speaker 1: there's still an enormous amount of hydrogen left over, and

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Speaker 1: that's why the star doesn't die in a quiet fizzle.

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Speaker 1: It's not just like burning through all of its fuel.

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Speaker 1: But what's happening is that this balance between gravity and

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Speaker 1: fusion is getting upset. And there's really two different kinds

428
00:24:44,320 --> 00:24:46,639
Speaker 1: of supernova is that we should talk about. One of

429
00:24:46,640 --> 00:24:49,560
Speaker 1: them is called core collapse, and what happens there is

430
00:24:49,600 --> 00:24:53,960
Speaker 1: that the star is making this ash, this product of fusion,

431
00:24:54,000 --> 00:24:57,080
Speaker 1: making heavier and heavier elements which then settle at the

432
00:24:57,080 --> 00:24:59,280
Speaker 1: heart of the star. And if the star is not

433
00:24:59,440 --> 00:25:02,720
Speaker 1: heavy enough to create the high temperatures needed to burn

434
00:25:02,800 --> 00:25:06,400
Speaker 1: that into something even heavier than it's like inert material

435
00:25:06,480 --> 00:25:08,480
Speaker 1: at the heart of the star. So now at the

436
00:25:08,520 --> 00:25:10,879
Speaker 1: heart of the star you are no longer producing a

437
00:25:10,960 --> 00:25:13,600
Speaker 1: lot of energy, and so this balance between gravity and

438
00:25:13,680 --> 00:25:18,040
Speaker 1: fusion tips towards gravity, and gravity rushes in and collapses

439
00:25:18,119 --> 00:25:20,800
Speaker 1: the star. The star collapses, but it doesn't just like

440
00:25:20,920 --> 00:25:24,600
Speaker 1: suddenly go out. Collapse makes it super dense and so

441
00:25:24,640 --> 00:25:28,119
Speaker 1: super hot inside the star and quickly burns through a

442
00:25:28,280 --> 00:25:32,000
Speaker 1: huge amount of fuel. So first gravity is the upper

443
00:25:32,040 --> 00:25:35,760
Speaker 1: hand to cause this collapse, but then fusion surges back

444
00:25:35,800 --> 00:25:38,239
Speaker 1: and blows it outwards again, and it leaves behind a

445
00:25:38,440 --> 00:25:40,640
Speaker 1: very dense core which is gonna be a black hole

446
00:25:40,840 --> 00:25:43,679
Speaker 1: or a neutron star. So you mentioned earlier that it

447
00:25:43,760 --> 00:25:48,000
Speaker 1: is it's this push and shove kind of where gravity

448
00:25:48,080 --> 00:25:51,320
Speaker 1: is trying to push it inwards like almost to create

449
00:25:51,359 --> 00:25:53,600
Speaker 1: like a black hole, and then there's the push out.

450
00:25:53,960 --> 00:25:57,840
Speaker 1: And so once that outward pushing is like outweighed by

451
00:25:57,840 --> 00:26:01,680
Speaker 1: the inward pushing, the heaviness of the inward pushing. Why

452
00:26:01,720 --> 00:26:04,960
Speaker 1: doesn't it just become a black hole all the time? Right?

453
00:26:05,000 --> 00:26:07,840
Speaker 1: So gravity wants to make everything a black hole. Right.

454
00:26:07,880 --> 00:26:10,840
Speaker 1: Gravity can only do one thing, which is pulls stuff together,

455
00:26:10,960 --> 00:26:13,480
Speaker 1: and if there was only gravity in the universe, eventually

456
00:26:13,760 --> 00:26:16,119
Speaker 1: it would just make everything into a black hole. The

457
00:26:16,200 --> 00:26:18,640
Speaker 1: reason that things aren't a black holes that there's some

458
00:26:18,680 --> 00:26:21,679
Speaker 1: way to resist it. Like why isn't the Earth a

459
00:26:21,720 --> 00:26:24,119
Speaker 1: black hole? It's a big blob of mass. Why doesn't

460
00:26:24,160 --> 00:26:27,240
Speaker 1: gravity squeeze it down into a peanut and make it

461
00:26:27,320 --> 00:26:29,439
Speaker 1: a black hole? The answer is that the Earth is

462
00:26:29,480 --> 00:26:33,520
Speaker 1: structurally strong enough to resist gravity. Gravity actually kind of

463
00:26:33,520 --> 00:26:36,960
Speaker 1: a weakling, not really a very powerful force. It's like

464
00:26:37,080 --> 00:26:40,200
Speaker 1: ten to the thirty times weaker than all the other forces.

465
00:26:40,320 --> 00:26:43,000
Speaker 1: So you just need something to be able to resist it.

466
00:26:43,080 --> 00:26:46,000
Speaker 1: So fusion can resist it for a long time, but eventually,

467
00:26:46,040 --> 00:26:48,560
Speaker 1: as the star gets more and more massive at its core,

468
00:26:48,720 --> 00:26:51,679
Speaker 1: gravity is winning and fusion is losing. So what happens

469
00:26:51,680 --> 00:26:54,280
Speaker 1: when a supernova collapse? Sometimes you do get a black

470
00:26:54,320 --> 00:26:56,600
Speaker 1: hole at its heart. It depends on the mass of

471
00:26:56,640 --> 00:27:00,359
Speaker 1: the original star. Sometimes you get a black hole. Sometimes, however,

472
00:27:00,440 --> 00:27:03,600
Speaker 1: there's another stage, like a neutron star can be formed,

473
00:27:03,640 --> 00:27:06,560
Speaker 1: So the incredible dense core that's left over after the

474
00:27:06,600 --> 00:27:10,159
Speaker 1: supernova happens can be another kind of matter which resists

475
00:27:10,280 --> 00:27:13,520
Speaker 1: collapse into a black hole. But again, neutron stars are

476
00:27:13,560 --> 00:27:16,000
Speaker 1: not something that we understand very well. We did an

477
00:27:16,040 --> 00:27:19,920
Speaker 1: episode recently about what's inside a neutron star. It's something

478
00:27:19,920 --> 00:27:22,520
Speaker 1: that scientists are still exploring. So it's sort of like

479
00:27:22,560 --> 00:27:25,160
Speaker 1: a ladder of ways that you can avoid black hole

480
00:27:25,200 --> 00:27:27,520
Speaker 1: collapse if you can make the right kind of matter,

481
00:27:27,640 --> 00:27:29,520
Speaker 1: or you can sort of like hold up against the

482
00:27:29,560 --> 00:27:32,760
Speaker 1: trash compactor of gravity trying to squeeze you down into

483
00:27:32,760 --> 00:27:35,399
Speaker 1: a black hole, So it could become a black hole,

484
00:27:35,600 --> 00:27:38,400
Speaker 1: could become something like a neutron star. Do we know

485
00:27:38,480 --> 00:27:41,840
Speaker 1: like why it becomes a supernova sometimes, like what would

486
00:27:41,920 --> 00:27:46,119
Speaker 1: cause that explosion rather than it just collapsing. So supernova

487
00:27:46,160 --> 00:27:48,320
Speaker 1: is when it starts to collapse. It's like an implosion

488
00:27:48,480 --> 00:27:51,240
Speaker 1: and you get this shock wave that's traveling towards the

489
00:27:51,280 --> 00:27:53,359
Speaker 1: center of the star and then it hits the core

490
00:27:53,520 --> 00:27:56,480
Speaker 1: and it bounces back and you get the supersonic shock

491
00:27:56,520 --> 00:27:59,840
Speaker 1: wave that comes out and blows out all of this material,

492
00:28:00,040 --> 00:28:02,479
Speaker 1: huge amounts of light are released because you have a

493
00:28:02,520 --> 00:28:04,840
Speaker 1: lot of fusion happening all at once. You know, a

494
00:28:04,880 --> 00:28:07,680
Speaker 1: star is like a very slow burn, using a very

495
00:28:07,760 --> 00:28:11,439
Speaker 1: tiny fraction of its fuel every year, and the supernovit

496
00:28:11,480 --> 00:28:13,760
Speaker 1: it can use of a big fraction of its fuel

497
00:28:13,920 --> 00:28:16,600
Speaker 1: all at once, which is how it can become brighter

498
00:28:16,600 --> 00:28:20,359
Speaker 1: than the entire galaxy around it. It also spews a

499
00:28:20,359 --> 00:28:22,920
Speaker 1: lot of that material out into space. So you have

500
00:28:23,000 --> 00:28:26,840
Speaker 1: this implosion that creates very high temperatures, very briefly, a

501
00:28:26,880 --> 00:28:29,560
Speaker 1: lot of really really rapid fusion, and then it blows

502
00:28:29,640 --> 00:28:31,840
Speaker 1: up and sends a lot of that energy in terms

503
00:28:31,840 --> 00:28:34,879
Speaker 1: of photons and protons and just like raw star stuff

504
00:28:35,160 --> 00:28:39,640
Speaker 1: out into space. So just a hypothetical, it'd be like

505
00:28:40,080 --> 00:28:44,320
Speaker 1: a kid throwing a ball against a wall really hard,

506
00:28:44,920 --> 00:28:48,240
Speaker 1: and again hypothetically the ball like shooting back out because

507
00:28:48,280 --> 00:28:50,080
Speaker 1: you threw it against the wall really hard and hitting

508
00:28:50,080 --> 00:28:54,000
Speaker 1: you in the face. But that times like a billion

509
00:28:54,520 --> 00:28:58,440
Speaker 1: with a billion children and a billion balls. Yeah, and

510
00:28:58,480 --> 00:29:00,960
Speaker 1: it's not something that we can under stand because there's

511
00:29:01,000 --> 00:29:03,880
Speaker 1: a lot of really strong forces involved and it's all

512
00:29:03,920 --> 00:29:06,840
Speaker 1: of very fast physics. So you know, we can't look

513
00:29:06,840 --> 00:29:09,400
Speaker 1: at a star and say this one's gonna go supernova

514
00:29:09,480 --> 00:29:12,560
Speaker 1: in forty two point two billion years, or this one's

515
00:29:12,600 --> 00:29:15,120
Speaker 1: gonna go supernova tomorrow. It's the kind of thing we

516
00:29:15,200 --> 00:29:17,920
Speaker 1: just sort of like see happening, and we're like, oh, everybody,

517
00:29:17,920 --> 00:29:20,640
Speaker 1: watch that one. Watch that one, and we're trying to

518
00:29:20,720 --> 00:29:23,360
Speaker 1: understand what goes on inside it. But modeling the process

519
00:29:23,360 --> 00:29:26,360
Speaker 1: of a supernova is not something we're capable of yet.

520
00:29:26,440 --> 00:29:28,760
Speaker 1: You know, when we want to understand something in physics,

521
00:29:28,800 --> 00:29:32,160
Speaker 1: either we find like a set of equations that describe

522
00:29:32,160 --> 00:29:35,240
Speaker 1: it very simply, like F equals m A that ignores

523
00:29:35,280 --> 00:29:37,480
Speaker 1: a lot of the details of the particles that's going

524
00:29:37,480 --> 00:29:41,400
Speaker 1: on inside, or we do like really complicated calculations using

525
00:29:41,400 --> 00:29:44,440
Speaker 1: a computer to model all of those details and see

526
00:29:44,440 --> 00:29:46,680
Speaker 1: if we can describe the sort of big picture that

527
00:29:46,720 --> 00:29:48,960
Speaker 1: comes out. So far, we haven't found a simple set

528
00:29:48,960 --> 00:29:52,240
Speaker 1: of equations to describe supernova, and we don't have the

529
00:29:52,240 --> 00:29:55,600
Speaker 1: computing power necessary yet to like come up with a

530
00:29:55,640 --> 00:29:58,960
Speaker 1: basic model of the innards and understand how that describes

531
00:29:59,000 --> 00:30:01,720
Speaker 1: a supernova. So we're still really learning about how this

532
00:30:01,760 --> 00:30:04,120
Speaker 1: stuff works. So it sounds like if we want to

533
00:30:04,160 --> 00:30:07,040
Speaker 1: catch a supernova, we have to kind of stay frosty

534
00:30:07,120 --> 00:30:10,240
Speaker 1: and keep watching the sky, which I mean, we haven't

535
00:30:10,280 --> 00:30:12,560
Speaker 1: done that in like half an hour, so we should

536
00:30:12,560 --> 00:30:15,120
Speaker 1: probably take a break and check just to make sure

537
00:30:15,560 --> 00:30:32,680
Speaker 1: one hasn't happened while we've been talking, right, absolutely, all right,

538
00:30:32,760 --> 00:30:38,400
Speaker 1: I looked outside, bad news, not yet, and you might

539
00:30:38,440 --> 00:30:41,400
Speaker 1: wonder maybe Katie missed her supernova? Right. The amazing thing

540
00:30:41,400 --> 00:30:43,920
Speaker 1: about a supernova is that they're not just a flash

541
00:30:44,400 --> 00:30:47,920
Speaker 1: like they last for sometimes weeks or months. I mean,

542
00:30:47,960 --> 00:30:50,600
Speaker 1: there's sort of a flash on the cosmic time scale,

543
00:30:51,240 --> 00:30:53,880
Speaker 1: but for a human they can really last for quite

544
00:30:53,880 --> 00:30:56,360
Speaker 1: a long time. So if there's a supernova in the sky,

545
00:30:56,600 --> 00:30:58,440
Speaker 1: you could miss it today, you could miss it tomorrow.

546
00:30:58,480 --> 00:31:00,600
Speaker 1: You might even be able to ignore for a week

547
00:31:00,840 --> 00:31:03,120
Speaker 1: and then eventually look up and catch it up there

548
00:31:03,200 --> 00:31:06,000
Speaker 1: in the sky shining its photons at you. So it

549
00:31:06,080 --> 00:31:10,400
Speaker 1: seems like if we have like billions of observers, we

550
00:31:10,480 --> 00:31:14,160
Speaker 1: should catch it if it happens. And have we ever

551
00:31:14,240 --> 00:31:16,840
Speaker 1: caught one? So we have seen supernova and in fact,

552
00:31:16,840 --> 00:31:19,160
Speaker 1: they are so dramatic that you don't even have to

553
00:31:19,240 --> 00:31:22,719
Speaker 1: just look at Like the recent period of modern astronomy,

554
00:31:22,960 --> 00:31:26,600
Speaker 1: when we have space telescopes and incredible ground based telescopes

555
00:31:26,640 --> 00:31:30,600
Speaker 1: and all these new digital technologies to see supernova. People

556
00:31:30,640 --> 00:31:34,080
Speaker 1: have been seeing supernova in the sky for thousands of

557
00:31:34,240 --> 00:31:37,800
Speaker 1: years because sometimes they're just obvious. You know, if all

558
00:31:37,840 --> 00:31:40,320
Speaker 1: of a sudden there's an incredible bright new star in

559
00:31:40,360 --> 00:31:44,120
Speaker 1: the sky outshining everything else, then people are gonna see that,

560
00:31:44,200 --> 00:31:46,440
Speaker 1: and they're gonna say something to each other, and it's

561
00:31:46,440 --> 00:31:49,560
Speaker 1: gonna show up in historical records that people have done

562
00:31:49,600 --> 00:31:53,080
Speaker 1: a deep dive into the history of astronomy and found

563
00:31:53,160 --> 00:31:55,240
Speaker 1: times when locals have looked up in the sky and

564
00:31:55,320 --> 00:31:57,760
Speaker 1: seen something they didn't understand and wrote it down, and

565
00:31:57,800 --> 00:32:02,760
Speaker 1: we can now reinterpret those writings as evidence for supernova.

566
00:32:03,000 --> 00:32:06,440
Speaker 1: I can't imagine what I would be thinking like before.

567
00:32:06,960 --> 00:32:09,320
Speaker 1: I mean, I mean, if I saw a supernova today,

568
00:32:09,440 --> 00:32:12,120
Speaker 1: let's be honest, I would also be surprised and scared.

569
00:32:12,240 --> 00:32:14,680
Speaker 1: But back then even more so. If I didn't have

570
00:32:14,880 --> 00:32:17,280
Speaker 1: physicists like you telling me what was going on, I'd

571
00:32:17,280 --> 00:32:22,080
Speaker 1: probably think this guy was like really angry at me. Yeah,

572
00:32:22,160 --> 00:32:24,640
Speaker 1: it's hard to put yourself in the minds of these folks,

573
00:32:24,840 --> 00:32:27,520
Speaker 1: which is why it's really interesting to read these things,

574
00:32:27,560 --> 00:32:29,080
Speaker 1: like what does it mean for them? How do they

575
00:32:29,080 --> 00:32:32,480
Speaker 1: describe it what questions were they asking about this kind

576
00:32:32,520 --> 00:32:35,400
Speaker 1: of thing. It gives you not just a picture into

577
00:32:35,560 --> 00:32:38,240
Speaker 1: what supernovas are doing and how often they happened, but

578
00:32:38,320 --> 00:32:41,680
Speaker 1: also you know what people are doing, what they are thinking,

579
00:32:41,800 --> 00:32:46,360
Speaker 1: their relationship with the night sky itself super fun. So

580
00:32:46,840 --> 00:32:49,080
Speaker 1: how do we know? Because, like we we have a

581
00:32:49,280 --> 00:32:52,920
Speaker 1: history of things. We have written and drawn histories and

582
00:32:53,040 --> 00:32:56,000
Speaker 1: also oral histories. But there's a lot I think lost

583
00:32:56,040 --> 00:32:59,200
Speaker 1: in translation. And if someone described something, they're not going

584
00:32:59,240 --> 00:33:02,000
Speaker 1: to say, oh, saw a supernova last week it was

585
00:33:02,040 --> 00:33:04,720
Speaker 1: pretty cool. You know, They're going to describe it in

586
00:33:04,880 --> 00:33:07,640
Speaker 1: terms that they understand at the time. So how do

587
00:33:07,680 --> 00:33:10,920
Speaker 1: we know what they're describing is something like a supernova?

588
00:33:11,040 --> 00:33:13,160
Speaker 1: So we can't always know, but it depends on sort

589
00:33:13,160 --> 00:33:15,040
Speaker 1: of the quality of the notes that we're looking at.

590
00:33:15,160 --> 00:33:17,400
Speaker 1: And some of these things are a little speculative, and

591
00:33:17,400 --> 00:33:19,640
Speaker 1: in other cases people took really good notes and they

592
00:33:19,640 --> 00:33:22,840
Speaker 1: described something that we really can't otherwise explain. You know.

593
00:33:22,880 --> 00:33:25,960
Speaker 1: It's like, let's get into the details of the earliest

594
00:33:26,080 --> 00:33:29,400
Speaker 1: record we have that might be a supernova comes from

595
00:33:29,560 --> 00:33:34,160
Speaker 1: forty five hundred b C. This is like sixty hundred

596
00:33:34,320 --> 00:33:38,080
Speaker 1: years ago. Is a rock carving found in Kashmir in

597
00:33:38,080 --> 00:33:41,280
Speaker 1: India that people think depicts what is a hunting scene

598
00:33:41,560 --> 00:33:44,960
Speaker 1: with two very bright objects in the sky. The idea

599
00:33:45,000 --> 00:33:48,120
Speaker 1: is that it looks like a sky with two sons.

600
00:33:48,440 --> 00:33:50,600
Speaker 1: I mean, if you were out hunting in the old

601
00:33:50,680 --> 00:33:53,440
Speaker 1: days and saw a second son in the sky, you

602
00:33:53,520 --> 00:33:56,160
Speaker 1: might also be inspired to make a drawing of it.

603
00:33:56,480 --> 00:33:59,320
Speaker 1: So it's not exactly a hundred percent, but this might

604
00:33:59,440 --> 00:34:03,080
Speaker 1: be the least record of a supernova observation. And then

605
00:34:03,280 --> 00:34:06,080
Speaker 1: note taking now I am looking at this drawing and

606
00:34:06,160 --> 00:34:10,680
Speaker 1: it does look like two really bright suns in the

607
00:34:10,719 --> 00:34:16,040
Speaker 1: sky or or hear me out giant eyeball like eyeball

608
00:34:16,120 --> 00:34:19,759
Speaker 1: aliens with tentacles. Yeah, exactly. It's far from something you

609
00:34:19,800 --> 00:34:23,160
Speaker 1: would accept is like figure one in a scientific paper,

610
00:34:23,320 --> 00:34:25,680
Speaker 1: you know, But it's fun to think about what these

611
00:34:25,719 --> 00:34:28,000
Speaker 1: folks were imagining and what it was like for them,

612
00:34:28,080 --> 00:34:30,400
Speaker 1: Like was this so bright that they could see it

613
00:34:30,480 --> 00:34:33,360
Speaker 1: in the daytime? Itself? Like really a second son in

614
00:34:33,440 --> 00:34:37,400
Speaker 1: this guy, It's possible, you know. The most reliable ancient

615
00:34:37,400 --> 00:34:41,720
Speaker 1: recording of a supernova comes from Chinese astronomers. They noted

616
00:34:41,760 --> 00:34:45,200
Speaker 1: it in one five the appearance of a bright star

617
00:34:45,360 --> 00:34:48,080
Speaker 1: in the sky, and they observed that it took about

618
00:34:48,160 --> 00:34:51,440
Speaker 1: eight months to fade from the sky, and it sparkled

619
00:34:51,600 --> 00:34:54,760
Speaker 1: just like a star, and it didn't move like a comet.

620
00:34:55,280 --> 00:34:58,359
Speaker 1: And so this scene really matches what we expect from

621
00:34:58,400 --> 00:35:01,800
Speaker 1: a supernova. It's very bright, it doesn't move like a comet,

622
00:35:02,000 --> 00:35:04,640
Speaker 1: it sparkles like a star. It fades on the timescale

623
00:35:04,680 --> 00:35:07,840
Speaker 1: of weeks or months. So this very likely was a

624
00:35:07,880 --> 00:35:11,400
Speaker 1: supernova captured by those Chinese astronomers. So when they're looking

625
00:35:11,440 --> 00:35:14,800
Speaker 1: at this doesn't look like just kind of an extra

626
00:35:14,880 --> 00:35:19,720
Speaker 1: bright star or is it just astoundingly bright, like almost

627
00:35:19,800 --> 00:35:23,560
Speaker 1: having a little sun in the sky at night or something.

628
00:35:23,880 --> 00:35:27,360
Speaker 1: It depends exactly on where the supernova is, and so

629
00:35:27,520 --> 00:35:30,600
Speaker 1: if it's in another galaxy, remember that our galaxy is

630
00:35:30,600 --> 00:35:33,839
Speaker 1: like a hundred thousand light years across, but other galaxies

631
00:35:33,880 --> 00:35:37,239
Speaker 1: are millions of light years away. So if a supernova

632
00:35:37,280 --> 00:35:40,000
Speaker 1: happens in another galaxy, then that star is going to

633
00:35:40,120 --> 00:35:43,640
Speaker 1: go from invisible to visible at night. If it happens

634
00:35:43,680 --> 00:35:46,560
Speaker 1: in our galaxy, then the supernova is going to go

635
00:35:46,600 --> 00:35:48,400
Speaker 1: from like a star you can see at night to

636
00:35:48,480 --> 00:35:50,920
Speaker 1: a star you might be able to see in the daytime,

637
00:35:51,239 --> 00:35:54,400
Speaker 1: depending exactly on how close it is so yeah, this

638
00:35:54,440 --> 00:35:58,000
Speaker 1: could appear like a second son if a nearby star

639
00:35:58,239 --> 00:36:01,240
Speaker 1: goes supernova, because remember us, supernova can be as bright

640
00:36:01,280 --> 00:36:04,760
Speaker 1: as the entire galaxy. It can be a hundred billion

641
00:36:04,880 --> 00:36:08,360
Speaker 1: times brighter than our sun. Would we be in trouble?

642
00:36:08,400 --> 00:36:11,120
Speaker 1: Are there any stars that would cause us a little

643
00:36:11,120 --> 00:36:13,920
Speaker 1: bit of trouble here on Earth if it went supernova?

644
00:36:14,040 --> 00:36:17,080
Speaker 1: Oh yeah, if Proximus Centauri went supernova, we would be

645
00:36:17,239 --> 00:36:20,799
Speaker 1: quite literally toasted because the amount of energy and radiation

646
00:36:20,920 --> 00:36:23,520
Speaker 1: would really fry at least one half of the Earth,

647
00:36:23,560 --> 00:36:25,480
Speaker 1: you know, the half the Earth that was in the

648
00:36:25,520 --> 00:36:27,960
Speaker 1: direction of that star at the time. The rest of us,

649
00:36:28,080 --> 00:36:31,680
Speaker 1: having like an entire Earth shielding us from the supernova,

650
00:36:31,800 --> 00:36:34,520
Speaker 1: would probably be fine until, of course, the Earth's one

651
00:36:34,600 --> 00:36:36,960
Speaker 1: around and roasted the other half. So we're sort of

652
00:36:37,000 --> 00:36:39,759
Speaker 1: like rotisserie Earth. We just have to kind of like

653
00:36:40,200 --> 00:36:43,839
Speaker 1: all move to that side and keep moving, you know,

654
00:36:43,920 --> 00:36:47,920
Speaker 1: like hamsters and a hamster wheel of death. While I'll

655
00:36:47,960 --> 00:36:50,719
Speaker 1: be adding that to my long list of things that

656
00:36:50,840 --> 00:36:55,719
Speaker 1: I cannot directly change but cause me existential dreads so great.

657
00:36:55,840 --> 00:36:58,320
Speaker 1: It also sounds like a great pitch for a Netflix show.

658
00:36:58,400 --> 00:37:01,920
Speaker 1: You know, entire cities on wheels rolling around the planet

659
00:37:01,960 --> 00:37:06,279
Speaker 1: to avoid the frying radiation. Yeah, like snow piercer, but

660
00:37:06,440 --> 00:37:11,439
Speaker 1: except it's like to escape the heat. Supernova piercer sounds good.

661
00:37:12,680 --> 00:37:14,880
Speaker 1: And so if we look back in the historical record,

662
00:37:14,920 --> 00:37:17,640
Speaker 1: there's like five of these things observed in like the

663
00:37:17,719 --> 00:37:20,280
Speaker 1: last thousand years. There was a time in a thousand

664
00:37:20,280 --> 00:37:23,359
Speaker 1: and six when people all over the world noticed one,

665
00:37:23,400 --> 00:37:27,120
Speaker 1: from China to Japan. Astronomers in Iraq and Egypt and

666
00:37:27,120 --> 00:37:29,840
Speaker 1: also in Europe noticed something they called a guest star

667
00:37:30,000 --> 00:37:34,319
Speaker 1: which appeared sorry they called it a guest star. Yeah,

668
00:37:34,480 --> 00:37:37,120
Speaker 1: like we have a sudden guest somebody said, another place

669
00:37:37,120 --> 00:37:40,440
Speaker 1: for dinner, welcome or not. I do like the idea

670
00:37:40,480 --> 00:37:43,200
Speaker 1: of like just on one of these night shows, you know,

671
00:37:43,400 --> 00:37:45,520
Speaker 1: Jimmy Fallon or whoever, it's like, oh, we got a

672
00:37:45,520 --> 00:37:48,480
Speaker 1: guest star, and then it's a supernova and everyone gets

673
00:37:48,480 --> 00:37:51,200
Speaker 1: fried exactly. Sometimes they just blow it all up. And

674
00:37:51,239 --> 00:37:53,120
Speaker 1: then as we enter in sort of like the more

675
00:37:53,239 --> 00:37:57,040
Speaker 1: modern historical period, we have folks whose names we know

676
00:37:57,080 --> 00:38:01,040
Speaker 1: well writing about these things. So Tico Bray noted one

677
00:38:01,120 --> 00:38:04,360
Speaker 1: in fifteen seventy two in the sky and took a

678
00:38:04,360 --> 00:38:06,960
Speaker 1: lot of great data. He's sort of famous for taking

679
00:38:06,960 --> 00:38:10,280
Speaker 1: meticulous notes about what he saw. What's interesting also about

680
00:38:10,280 --> 00:38:12,040
Speaker 1: this one is, like we said earlier, it helps us

681
00:38:12,080 --> 00:38:15,320
Speaker 1: think about what people thought about supernova at the time

682
00:38:15,560 --> 00:38:18,560
Speaker 1: and Europe around this time. Most people thought that the

683
00:38:18,640 --> 00:38:22,279
Speaker 1: cosmos beyond the moon and the planets couldn't change. They

684
00:38:22,280 --> 00:38:24,480
Speaker 1: thought it was just like out there static. You know,

685
00:38:24,520 --> 00:38:27,239
Speaker 1: the whole universe was a bunch of stars hung out

686
00:38:27,280 --> 00:38:30,040
Speaker 1: into space. They weren't even aware of the idea of

687
00:38:30,080 --> 00:38:34,040
Speaker 1: other galaxies, right. They thought the whole universe was infinitely old,

688
00:38:34,080 --> 00:38:37,320
Speaker 1: with stars not moving or changing. That was the idea

689
00:38:37,360 --> 00:38:40,000
Speaker 1: at the time, just kind of painted on a big

690
00:38:40,040 --> 00:38:43,200
Speaker 1: globe or something. Yeah, so this didn't really fit well

691
00:38:43,200 --> 00:38:45,000
Speaker 1: with the idea of supernova because this is like a

692
00:38:45,160 --> 00:38:48,600
Speaker 1: change in something. So they thought that probably of something

693
00:38:48,640 --> 00:38:52,080
Speaker 1: happening in the atmosphere. They thought supernovas were like weird

694
00:38:52,200 --> 00:38:55,880
Speaker 1: bright lights created like, you know, fifty miles above the surface,

695
00:38:56,040 --> 00:39:01,520
Speaker 1: instead of super duper far away swamp gas. Well ali exactly.

696
00:39:01,680 --> 00:39:03,719
Speaker 1: But you know, Bray took a lot of notes, and

697
00:39:03,760 --> 00:39:07,080
Speaker 1: he realized that this thing remains stationary from night tonight,

698
00:39:07,360 --> 00:39:10,319
Speaker 1: doesn't change. It's parallax, and so it has to be

699
00:39:10,400 --> 00:39:13,000
Speaker 1: really really far away, and so he wrote a book

700
00:39:13,000 --> 00:39:15,000
Speaker 1: with all of these details, and it's that book which

701
00:39:15,040 --> 00:39:17,640
Speaker 1: gave the name nova to things that appear in the

702
00:39:17,760 --> 00:39:20,080
Speaker 1: night sky. But then the last one that we've ever

703
00:39:20,160 --> 00:39:24,200
Speaker 1: seen coming from our galaxy was Kepler. He saw one

704
00:39:24,200 --> 00:39:26,719
Speaker 1: in sixteen o four, And so you know, here we

705
00:39:26,760 --> 00:39:29,160
Speaker 1: have to make a distinction. We are seeing supernova from

706
00:39:29,239 --> 00:39:32,080
Speaker 1: all over the universe because they are so bright that

707
00:39:32,200 --> 00:39:35,480
Speaker 1: we can also see them from other galaxies, but the

708
00:39:35,520 --> 00:39:37,680
Speaker 1: one we saw in sixteen o four was the last

709
00:39:37,680 --> 00:39:41,400
Speaker 1: one we've ever seen from the Milky Way itself. So

710
00:39:42,120 --> 00:39:45,560
Speaker 1: I haven't necessarily been keeping good track of the dates,

711
00:39:45,640 --> 00:39:49,240
Speaker 1: but had we been seeing them at a rate greater

712
00:39:49,320 --> 00:39:53,440
Speaker 1: than once every four hundred years before this point or no.

713
00:39:54,160 --> 00:39:56,719
Speaker 1: So we have some estimates for how likely it is

714
00:39:56,800 --> 00:39:59,919
Speaker 1: to create supernovas from watching other galaxies and from think

715
00:40:00,120 --> 00:40:02,919
Speaker 1: about the ones we've seen in our galaxy, and so

716
00:40:03,000 --> 00:40:05,960
Speaker 1: we estimate that in the Milky Way we should get

717
00:40:05,960 --> 00:40:09,920
Speaker 1: about one supernova every twenty years or so. The galaxy

718
00:40:09,920 --> 00:40:12,400
Speaker 1: of about a hundred billion stars should give us a

719
00:40:12,440 --> 00:40:15,719
Speaker 1: supernova every twenty years. So in the four hundred years

720
00:40:15,719 --> 00:40:19,799
Speaker 1: since Kepler's observation, we should have seen about twenty supernova

721
00:40:19,880 --> 00:40:22,439
Speaker 1: in the Milky Way, right, and you mentioned that we

722
00:40:22,640 --> 00:40:26,239
Speaker 1: saw like potentially saw like five in the past one

723
00:40:26,320 --> 00:40:30,359
Speaker 1: thousand years, So that'd be one every two hundred years, right,

724
00:40:30,480 --> 00:40:33,400
Speaker 1: not one every four hundred years. That's right. But we

725
00:40:33,440 --> 00:40:36,320
Speaker 1: don't think that the historical record is complete, right. We

726
00:40:36,360 --> 00:40:40,080
Speaker 1: don't think that we have found every written record of supernovas,

727
00:40:40,120 --> 00:40:42,160
Speaker 1: and also we don't think that people have seen all

728
00:40:42,160 --> 00:40:45,120
Speaker 1: the supernovas that were out there. But something we'll dig

729
00:40:45,160 --> 00:40:47,520
Speaker 1: into in a minute is like how often we expect

730
00:40:47,520 --> 00:40:49,799
Speaker 1: these things to happen, and how likely we are to

731
00:40:50,000 --> 00:40:53,480
Speaker 1: see one if it does happen in our galaxy. Right,

732
00:40:53,560 --> 00:40:58,319
Speaker 1: So we have this mystery of these missing supernovas, right

733
00:40:58,400 --> 00:41:01,920
Speaker 1: that if like we should be seeing one every maybe

734
00:41:01,920 --> 00:41:06,080
Speaker 1: twenty years, or at least more frequently than every four years.

735
00:41:06,400 --> 00:41:09,520
Speaker 1: But before we waste time trying to figure it out,

736
00:41:09,880 --> 00:41:13,520
Speaker 1: just a case it popped up while in the past,

737
00:41:13,600 --> 00:41:15,799
Speaker 1: like you know, fifteen minutes while we were discussing, I'm

738
00:41:15,800 --> 00:41:18,240
Speaker 1: gonna go out and check again, just make sure, because

739
00:41:18,239 --> 00:41:20,840
Speaker 1: then that that would settle it. Right. I'm so impressed

740
00:41:21,080 --> 00:41:23,799
Speaker 1: with how dutiful you are as a researcher. Yeah, yeah,

741
00:41:24,080 --> 00:41:27,000
Speaker 1: I'm gonna get up on the roof and stare right

742
00:41:27,040 --> 00:41:29,200
Speaker 1: into the sun for a little while. I will be

743
00:41:29,480 --> 00:41:45,400
Speaker 1: right back. Well, I am back. I stared right into

744
00:41:45,560 --> 00:41:47,960
Speaker 1: the sky directly at the Sun just so I wouldn't

745
00:41:48,080 --> 00:41:51,120
Speaker 1: miss the supernova if it happened, and I gotta tell

746
00:41:51,160 --> 00:41:54,760
Speaker 1: you was not one of my best ideas. I'm glad

747
00:41:54,800 --> 00:41:56,640
Speaker 1: that you're still back and you have everything you need

748
00:41:56,719 --> 00:41:58,919
Speaker 1: to continue podcasting, because you know, we don't really need

749
00:41:59,120 --> 00:42:03,719
Speaker 1: your eyeballs for podcast. Yes, the uh. I basically just

750
00:42:03,960 --> 00:42:07,160
Speaker 1: see a big glowing orb all the time, which is great.

751
00:42:07,480 --> 00:42:11,280
Speaker 1: So we were talking about there is this mystery because

752
00:42:11,320 --> 00:42:14,160
Speaker 1: it seems like we should be seeing these supernovas more often.

753
00:42:14,440 --> 00:42:17,040
Speaker 1: Not only in historical records, does it seem like there

754
00:42:17,080 --> 00:42:21,200
Speaker 1: were more supernovas, you know, not maybe one every two

755
00:42:21,280 --> 00:42:23,680
Speaker 1: hundred years or so, not one every four hundred years,

756
00:42:23,680 --> 00:42:27,760
Speaker 1: but also there was a calculation done to see how

757
00:42:27,800 --> 00:42:31,160
Speaker 1: often should we be seeing it, and that resulted in

758
00:42:31,239 --> 00:42:34,960
Speaker 1: about twenty years, right exactly. And remember we don't understand

759
00:42:35,040 --> 00:42:38,319
Speaker 1: supernovas very well, so it's hard to predict, sort of theoretically,

760
00:42:38,360 --> 00:42:40,879
Speaker 1: how often they should happen. But we can learn by

761
00:42:40,920 --> 00:42:43,319
Speaker 1: looking at all the other galaxies to try to get

762
00:42:43,320 --> 00:42:46,040
Speaker 1: a sense for the rate of supernovas. So remember, we

763
00:42:46,080 --> 00:42:48,960
Speaker 1: can see supernovas in our galaxy even just using the

764
00:42:49,040 --> 00:42:52,239
Speaker 1: naked eye, going back thousands of years. But in the

765
00:42:52,280 --> 00:42:54,839
Speaker 1: more recent era, because we have telescopes, we could now

766
00:42:54,920 --> 00:42:59,160
Speaker 1: study very thoroughly supernovas in other galaxies. So, starting in

767
00:42:59,200 --> 00:43:02,640
Speaker 1: the nine or so, people began these campaigns to scan

768
00:43:02,800 --> 00:43:07,600
Speaker 1: the sky for new stars appearing in other galaxies using telescopes,

769
00:43:07,760 --> 00:43:10,399
Speaker 1: and they saw dozens and so we have definitely seen

770
00:43:10,440 --> 00:43:14,960
Speaker 1: supernovas recently. For example, we saw one in seven that

771
00:43:15,080 --> 00:43:17,960
Speaker 1: came from a large Magellanic cloud. This was one you

772
00:43:18,000 --> 00:43:20,200
Speaker 1: could actually see with the naked eye, even though it

773
00:43:20,320 --> 00:43:23,160
Speaker 1: wasn't in the Milky Way, because a large Magellanic cloud

774
00:43:23,280 --> 00:43:25,760
Speaker 1: is a satellite of the Milky Way, so it wasn't

775
00:43:25,800 --> 00:43:29,759
Speaker 1: that far away. So we're seeing supernovas in other galaxies,

776
00:43:30,040 --> 00:43:32,799
Speaker 1: and that lets us estimate what we think is the

777
00:43:32,920 --> 00:43:35,919
Speaker 1: rate of supernovas we should expect in the Milky Way,

778
00:43:36,239 --> 00:43:39,279
Speaker 1: being about one every twenty years. You know, there's still

779
00:43:39,280 --> 00:43:41,600
Speaker 1: a lot of uncertainty in that number, and so then

780
00:43:41,640 --> 00:43:44,319
Speaker 1: the question is, you know, are they not happening in

781
00:43:44,360 --> 00:43:47,279
Speaker 1: the Milky Way, or are we just not seeing them,

782
00:43:47,760 --> 00:43:50,920
Speaker 1: are they hiding it from us? Or maybe the Milky

783
00:43:50,920 --> 00:43:54,760
Speaker 1: Way is super weird and doesn't make supernovas as often

784
00:43:54,800 --> 00:43:57,600
Speaker 1: as these other neighboring galaxies. Right these are like just

785
00:43:57,680 --> 00:44:00,960
Speaker 1: the basic questions we have about supernove is because we're

786
00:44:01,000 --> 00:44:04,400
Speaker 1: so clueless about the thing that triggers them, the moment

787
00:44:04,480 --> 00:44:07,759
Speaker 1: that the star decides to collapse, and exactly what's going

788
00:44:07,800 --> 00:44:11,880
Speaker 1: on inside. I mean, it seems odd though, for like

789
00:44:11,920 --> 00:44:16,920
Speaker 1: an entire galaxy to have different rules from another galaxy,

790
00:44:17,000 --> 00:44:19,520
Speaker 1: or is that not so odd? It would be odd,

791
00:44:19,600 --> 00:44:22,600
Speaker 1: But there are odd galaxies out there. There are galaxies

792
00:44:22,600 --> 00:44:24,719
Speaker 1: that have lots of dark matter and galaxies that have

793
00:44:24,840 --> 00:44:27,840
Speaker 1: very little dark matter. They're huge galaxies and little galaxies.

794
00:44:27,880 --> 00:44:30,600
Speaker 1: There are galaxies that are still making stars and galaxies

795
00:44:30,600 --> 00:44:33,760
Speaker 1: that are quenched that will no longer be producing stars.

796
00:44:33,800 --> 00:44:36,000
Speaker 1: And we just don't know if the Milky Way is

797
00:44:36,040 --> 00:44:38,439
Speaker 1: typical or not, the same way we don't know if

798
00:44:38,520 --> 00:44:41,799
Speaker 1: Earth is typical or if it's weird and rare in

799
00:44:41,840 --> 00:44:44,479
Speaker 1: the universe. These are the kind of questions we get

800
00:44:44,520 --> 00:44:47,200
Speaker 1: to ask as we look out deep into the universe

801
00:44:47,400 --> 00:44:50,320
Speaker 1: to try to figure out whether our context is normal

802
00:44:50,600 --> 00:44:53,040
Speaker 1: or really really weird. But we can do more than

803
00:44:53,080 --> 00:44:56,360
Speaker 1: just look for supernovas as they happen. We can actually

804
00:44:56,440 --> 00:44:59,799
Speaker 1: also look for supernovas that have happened that we might

805
00:44:59,840 --> 00:45:03,600
Speaker 1: have missed because we can see supernova remnants. When a

806
00:45:03,640 --> 00:45:06,760
Speaker 1: supernova happens, it's very bright, it's very dramatic, but also

807
00:45:06,880 --> 00:45:10,520
Speaker 1: it creates this shock wave that shoots out into the universe,

808
00:45:10,719 --> 00:45:13,840
Speaker 1: leaving a sort of interesting fingerprint that you can continue

809
00:45:13,880 --> 00:45:17,120
Speaker 1: to see four hundreds or thousands of years later. So

810
00:45:17,160 --> 00:45:19,600
Speaker 1: it's kind of like looking at a star's kind of

811
00:45:19,680 --> 00:45:23,440
Speaker 1: fossil record exactly. Because when a supernova happens, remember, it

812
00:45:23,480 --> 00:45:28,040
Speaker 1: shoots out like several solar masses worth of stuff, right, Like,

813
00:45:28,200 --> 00:45:31,080
Speaker 1: think about what that means. A solar mass is an

814
00:45:31,239 --> 00:45:33,920
Speaker 1: entire sun's worth of stuff. And so now you have

815
00:45:33,920 --> 00:45:37,279
Speaker 1: a supernova shooting out like several times the mass of

816
00:45:37,280 --> 00:45:40,439
Speaker 1: the Sun, just in plasma and hot gas out into

817
00:45:40,440 --> 00:45:45,080
Speaker 1: the universe and incredibly high speeds, like significant fractions of

818
00:45:45,120 --> 00:45:47,680
Speaker 1: the speed of light. So what happens is that it's

819
00:45:47,680 --> 00:45:49,920
Speaker 1: going to smash into all the stuff around it. Space

820
00:45:50,040 --> 00:45:53,400
Speaker 1: is not totally empty, it's filled with the interstellar medium.

821
00:45:53,440 --> 00:45:56,080
Speaker 1: Which is like a very dilute gas, but when the

822
00:45:56,120 --> 00:45:59,919
Speaker 1: supernova remnants smash into it, you get this expanding shell

823
00:46:00,520 --> 00:46:02,759
Speaker 1: of a shock wave. So that's what we call a

824
00:46:02,840 --> 00:46:06,560
Speaker 1: supernova remnant. It's very distinctive. And scientists have looked out

825
00:46:06,600 --> 00:46:09,640
Speaker 1: into the night sky and for example, in our galaxy

826
00:46:09,800 --> 00:46:12,920
Speaker 1: in Cassiopeia, they see a remnant which looks to be

827
00:46:13,000 --> 00:46:17,040
Speaker 1: about three hundred and twenty five years old, which means

828
00:46:17,320 --> 00:46:20,279
Speaker 1: they think there was a supernova there three hundred years

829
00:46:20,320 --> 00:46:23,440
Speaker 1: ago that everybody missed. Nobody saw it, but we can

830
00:46:23,440 --> 00:46:26,760
Speaker 1: see evidence that had happened, and it happened fairly recently,

831
00:46:27,360 --> 00:46:30,520
Speaker 1: so it's a It's an interesting thing because like as

832
00:46:30,719 --> 00:46:35,759
Speaker 1: kind of postmortem detectives of this star explosion, you can't

833
00:46:35,840 --> 00:46:39,000
Speaker 1: necessarily look just at the sight of where the star was.

834
00:46:39,080 --> 00:46:42,640
Speaker 1: You're looking at where the remnants go, right, So it's

835
00:46:42,719 --> 00:46:47,399
Speaker 1: this expanding force. It's not just like looking at where

836
00:46:47,440 --> 00:46:50,440
Speaker 1: the star died. You have to look far afield of

837
00:46:50,560 --> 00:46:53,960
Speaker 1: where the star has exploded to yeah, precisely. And this

838
00:46:53,960 --> 00:46:56,160
Speaker 1: stuff moves out, but it moves out much slower than

839
00:46:56,200 --> 00:46:58,520
Speaker 1: the speed of light. You know, it's pretty fast and

840
00:46:58,560 --> 00:47:01,360
Speaker 1: pretty energetic, but it sort of in the vicinity of

841
00:47:01,400 --> 00:47:05,239
Speaker 1: where it happened. It's not like looking at black hole collisions,

842
00:47:05,520 --> 00:47:08,040
Speaker 1: and we're getting evidence of that from gravitational waves that

843
00:47:08,080 --> 00:47:10,440
Speaker 1: travels at the speed of light directly to us. Now

844
00:47:10,480 --> 00:47:13,600
Speaker 1: we're looking at like stuff spewing out sideways from the

845
00:47:13,640 --> 00:47:17,560
Speaker 1: supernova ramming into something else and then sending us light

846
00:47:17,880 --> 00:47:21,320
Speaker 1: from that collision. So we're seeing this like shock wave

847
00:47:21,480 --> 00:47:24,640
Speaker 1: emanate from the supernova, and we're seeing light from that

848
00:47:24,640 --> 00:47:27,960
Speaker 1: shock wave as it bounces into gas and heats it up.

849
00:47:28,040 --> 00:47:30,560
Speaker 1: So it's pretty cool. You can tell that as supernova

850
00:47:30,640 --> 00:47:32,480
Speaker 1: was there. It's sort of like you missed an explosion,

851
00:47:32,560 --> 00:47:34,480
Speaker 1: but now you're looking at the burn marks on the

852
00:47:34,520 --> 00:47:38,959
Speaker 1: ground or something like that. Yeah, yeah, that's really interesting. Yeah,

853
00:47:38,960 --> 00:47:41,600
Speaker 1: and people have done scans for these kind of remnants

854
00:47:41,600 --> 00:47:44,040
Speaker 1: in our galaxies and they found a few. They found

855
00:47:44,040 --> 00:47:46,759
Speaker 1: this one in Cassiopeia. That found another one that they're

856
00:47:46,760 --> 00:47:49,520
Speaker 1: pretty sure happened at the end of the nineteenth century.

857
00:47:49,719 --> 00:47:52,120
Speaker 1: But you know, there's no records that anybody saw the

858
00:47:52,200 --> 00:47:55,680
Speaker 1: actual supernova. So all this kind of stuff lends credence

859
00:47:55,719 --> 00:47:59,000
Speaker 1: to the idea that maybe supernova's actually are happening in

860
00:47:59,040 --> 00:48:02,640
Speaker 1: our galaxy. We're just not seeing them right that they're

861
00:48:02,640 --> 00:48:05,840
Speaker 1: out there, they're blowing up, but we are missing the party.

862
00:48:06,120 --> 00:48:09,160
Speaker 1: But wait just a minute, because you said that they're

863
00:48:09,200 --> 00:48:13,200
Speaker 1: super bright. There's a lot of energy released, and our

864
00:48:13,239 --> 00:48:16,920
Speaker 1: galaxy isn't you know, too far away from us. So

865
00:48:16,960 --> 00:48:20,239
Speaker 1: how could we miss that? Did we podcast over it? This?

866
00:48:20,320 --> 00:48:23,480
Speaker 1: This is what I was worried about. It's because you

867
00:48:23,520 --> 00:48:26,600
Speaker 1: were napping. You know, you took a break, a nap

868
00:48:26,600 --> 00:48:29,400
Speaker 1: in a coffee, and you missed all the important datah

869
00:48:29,440 --> 00:48:33,200
Speaker 1: man I got like fomo on a galactic scale. Now, no, no,

870
00:48:33,280 --> 00:48:35,960
Speaker 1: don't feel bad. It's not because we're lazy. The issue,

871
00:48:36,080 --> 00:48:39,320
Speaker 1: like everything else, is probably location. You know, the galaxy

872
00:48:39,360 --> 00:48:42,239
Speaker 1: is not that big on a universal link scale, but

873
00:48:42,320 --> 00:48:45,840
Speaker 1: it's also not that transparent. You know, the galaxy is

874
00:48:45,880 --> 00:48:48,319
Speaker 1: a lot of gas and dust in it, and if

875
00:48:48,360 --> 00:48:51,480
Speaker 1: something happens on the other side of the galaxy, then

876
00:48:51,520 --> 00:48:54,279
Speaker 1: the center of the galaxy, which is a swirling maelstrom

877
00:48:54,640 --> 00:48:57,880
Speaker 1: of intensity and gas and dust and it's pretty opaque,

878
00:48:57,960 --> 00:49:00,279
Speaker 1: then we might not be able to see it. And

879
00:49:00,320 --> 00:49:02,640
Speaker 1: so some of these things might just be happening behind

880
00:49:02,800 --> 00:49:06,360
Speaker 1: big dust clouds or big gas clouds, and this dust

881
00:49:06,440 --> 00:49:10,120
Speaker 1: is really good at blocking the light. And unfortunately, the

882
00:49:10,200 --> 00:49:13,600
Speaker 1: places that have the most dust are the densest places,

883
00:49:13,640 --> 00:49:17,000
Speaker 1: which are also the places that supernova are most likely

884
00:49:17,120 --> 00:49:20,319
Speaker 1: to happen. So this really was a punishment for us

885
00:49:20,320 --> 00:49:24,160
Speaker 1: not cleaning our rooms. I knew it it might be.

886
00:49:24,239 --> 00:49:27,120
Speaker 1: You know, this is still really speculative. Is the kind

887
00:49:27,160 --> 00:49:30,280
Speaker 1: of explanation people are trying to understand if it works.

888
00:49:30,680 --> 00:49:33,320
Speaker 1: And I read a paper last week exploring this in detail,

889
00:49:33,360 --> 00:49:36,799
Speaker 1: trying to say, like, can we explain not having seen

890
00:49:36,880 --> 00:49:40,279
Speaker 1: supernova based on where the gas and dust are in

891
00:49:40,320 --> 00:49:43,880
Speaker 1: the galaxy? And they did a really interesting, very thorough study.

892
00:49:44,040 --> 00:49:47,160
Speaker 1: They have a model for where they think supernova should

893
00:49:47,200 --> 00:49:50,400
Speaker 1: happen based on where are the stars in the galaxy.

894
00:49:50,560 --> 00:49:52,719
Speaker 1: From that they get a sense for how much light

895
00:49:52,760 --> 00:49:55,200
Speaker 1: should have arrived on Earth from each of these supernova,

896
00:49:55,239 --> 00:49:57,839
Speaker 1: you know, how bright it was, how far away it was.

897
00:49:58,080 --> 00:50:00,680
Speaker 1: Then we have maps actually of where or the dust

898
00:50:00,920 --> 00:50:04,160
Speaker 1: is in the galaxy, right like where these clouds of

899
00:50:04,239 --> 00:50:07,600
Speaker 1: choking gas and dust that would obscure our view are sitting.

900
00:50:07,840 --> 00:50:10,359
Speaker 1: And then we can do a calculation and say where

901
00:50:10,360 --> 00:50:13,120
Speaker 1: do we expect to see supernova in our galaxy? And

902
00:50:13,160 --> 00:50:16,000
Speaker 1: where do we expect not to see them because the

903
00:50:16,040 --> 00:50:19,400
Speaker 1: gas and dust are blocking them, and drum roll, do

904
00:50:19,560 --> 00:50:21,920
Speaker 1: we have those results. We do have those results. I'm

905
00:50:21,960 --> 00:50:25,520
Speaker 1: looking at them right now from this paper, and interestingly,

906
00:50:25,560 --> 00:50:28,680
Speaker 1: the results are kind of a surprise. Most of the

907
00:50:28,760 --> 00:50:33,120
Speaker 1: supernova that we have seen in our galaxy actually land

908
00:50:33,160 --> 00:50:36,360
Speaker 1: in places where we didn't expect to see them because

909
00:50:36,360 --> 00:50:38,560
Speaker 1: either there actually was a lot of gas and dust,

910
00:50:38,600 --> 00:50:41,719
Speaker 1: which somehow they are mysteriously overpowering, or it's a place

911
00:50:41,719 --> 00:50:44,400
Speaker 1: where you don't expect to see many supernovas. So we

912
00:50:44,480 --> 00:50:47,759
Speaker 1: like saw a super rare supernova. It's not something that

913
00:50:47,800 --> 00:50:50,120
Speaker 1: we understand, and so it's the kind of moment in

914
00:50:50,160 --> 00:50:53,239
Speaker 1: science where we go, well, that didn't work. You know,

915
00:50:53,320 --> 00:50:56,040
Speaker 1: we have this data, have a basic model that doesn't

916
00:50:56,080 --> 00:51:00,600
Speaker 1: explain it. What's wrong? Probably something simple is wrong with

917
00:51:00,719 --> 00:51:04,240
Speaker 1: our model, our estimate of how often the supernova happen,

918
00:51:04,760 --> 00:51:07,279
Speaker 1: or our guests for where the dust is or how

919
00:51:07,320 --> 00:51:10,960
Speaker 1: transparent that dust is to the light from the supernova.

920
00:51:11,200 --> 00:51:14,040
Speaker 1: Something is going wrong with these models. But the upshot

921
00:51:14,080 --> 00:51:16,360
Speaker 1: is that we can't explain it. We do not understand

922
00:51:16,640 --> 00:51:19,080
Speaker 1: why we are seeing the supernova that we are seeing

923
00:51:19,200 --> 00:51:22,200
Speaker 1: and why we are not seeing supernova in some areas

924
00:51:22,200 --> 00:51:26,120
Speaker 1: of the galaxy. So the model was saying not necessarily

925
00:51:26,560 --> 00:51:30,960
Speaker 1: that the supernova was in the location where it couldn't happen,

926
00:51:31,000 --> 00:51:33,839
Speaker 1: but that it was unlikely for us to be able

927
00:51:33,880 --> 00:51:36,200
Speaker 1: to see it at this location. Some of the ones

928
00:51:36,239 --> 00:51:39,319
Speaker 1: that we have seen are happening in places where they

929
00:51:39,360 --> 00:51:42,120
Speaker 1: should be very very rare. Not impossible, but you know,

930
00:51:42,160 --> 00:51:44,920
Speaker 1: you should expect to see more supernova where there are

931
00:51:45,000 --> 00:51:48,520
Speaker 1: more stars. And if you look at the historical distribution

932
00:51:48,560 --> 00:51:51,839
Speaker 1: of supernova that we have seen in our galaxy, there's

933
00:51:51,880 --> 00:51:54,160
Speaker 1: a lot of them in places where there aren't very

934
00:51:54,200 --> 00:51:57,759
Speaker 1: many stars, which is kind of confusing. Are supernova more

935
00:51:57,800 --> 00:52:01,640
Speaker 1: likely to happen there, or maybe there's some structure to

936
00:52:01,680 --> 00:52:04,440
Speaker 1: the galaxy that we haven't described in our model, you know,

937
00:52:04,560 --> 00:52:07,920
Speaker 1: some like clusters of gas and dust that are creating

938
00:52:08,000 --> 00:52:12,200
Speaker 1: supernovas or blocking supernovas. Something else is missing from our

939
00:52:12,239 --> 00:52:14,880
Speaker 1: model to add to this recipe to give us a

940
00:52:14,920 --> 00:52:17,920
Speaker 1: depiction that matches what we actually see out there in

941
00:52:17,960 --> 00:52:21,479
Speaker 1: the night sky. Yeah, that's really interesting. Like I wonder

942
00:52:21,520 --> 00:52:23,440
Speaker 1: if it could even be something like, you know, if

943
00:52:23,680 --> 00:52:27,160
Speaker 1: a star that's more likely to go supernova is more

944
00:52:27,200 --> 00:52:30,560
Speaker 1: likely to be a loner. It could be because we

945
00:52:30,600 --> 00:52:33,759
Speaker 1: know also that there's a lot of difference in sort

946
00:52:33,800 --> 00:52:36,520
Speaker 1: of the wrong ingredients in the galaxy. You know, in

947
00:52:36,520 --> 00:52:39,280
Speaker 1: the center of the galaxy there are more heavy metals,

948
00:52:39,320 --> 00:52:41,560
Speaker 1: so the stars there are more metallic, and so the

949
00:52:41,640 --> 00:52:44,640
Speaker 1: galactic conditions are very different in the center of the

950
00:52:44,640 --> 00:52:48,240
Speaker 1: galaxy and the spiral arms, and then above the galactic plane.

951
00:52:48,480 --> 00:52:50,720
Speaker 1: So this is the kind of next round of research

952
00:52:50,880 --> 00:52:54,440
Speaker 1: is understanding, like what are the conditions to make supernova?

953
00:52:54,640 --> 00:52:56,799
Speaker 1: What are the conditions in the galaxy? Can we make

954
00:52:56,840 --> 00:52:59,080
Speaker 1: a model that explains why you might be getting more

955
00:52:59,120 --> 00:53:02,400
Speaker 1: supernova or maybe just why we're not seeing them? You know,

956
00:53:02,440 --> 00:53:04,960
Speaker 1: maybe this more structure to this gas and dust than

957
00:53:04,960 --> 00:53:07,839
Speaker 1: we thought we understood. But it's a great opportunity. Every

958
00:53:07,880 --> 00:53:10,760
Speaker 1: time you have something you don't understand is a chance

959
00:53:10,800 --> 00:53:13,840
Speaker 1: to refine your models and learn something new about the universe.

960
00:53:13,960 --> 00:53:15,720
Speaker 1: Maybe it's just something about the map of the gas

961
00:53:15,719 --> 00:53:18,440
Speaker 1: and dust, or you know, maybe like the discoveries of

962
00:53:18,520 --> 00:53:21,160
Speaker 1: dark matter, this is not something that we can resolve

963
00:53:21,200 --> 00:53:23,400
Speaker 1: with like a little tweak to our models. Maybe it's

964
00:53:23,400 --> 00:53:27,560
Speaker 1: gonna require something really big and new in our understanding

965
00:53:27,560 --> 00:53:30,720
Speaker 1: of the universe. Right, so you gotta double and maybe

966
00:53:30,719 --> 00:53:34,000
Speaker 1: even triple. Check your mouth first, make sure someone didn't

967
00:53:34,040 --> 00:53:37,359
Speaker 1: just forget to carry a one. And then maybe it's

968
00:53:37,400 --> 00:53:41,600
Speaker 1: a sign of some really interesting discovery or mystery about

969
00:53:42,200 --> 00:53:44,440
Speaker 1: the universe. And now we are lucky enough to have

970
00:53:44,520 --> 00:53:49,200
Speaker 1: other ways to see supernova, not just through light. Supernova

971
00:53:49,239 --> 00:53:52,880
Speaker 1: also produce a lot of radiation in new trinos for example,

972
00:53:53,160 --> 00:53:56,560
Speaker 1: In fact, most of the energy produced in a supernova

973
00:53:56,880 --> 00:54:01,120
Speaker 1: comes from new trinos something like that. The radiation from

974
00:54:01,120 --> 00:54:04,759
Speaker 1: the supernova is in the form of neutrinos, which are

975
00:54:04,800 --> 00:54:08,920
Speaker 1: these weird little particles that mostly pass through matter, ignoring us.

976
00:54:09,200 --> 00:54:13,560
Speaker 1: And in the supernova, we actually saw the new trinos

977
00:54:13,640 --> 00:54:16,719
Speaker 1: from the supernova first because they're produced at the heart

978
00:54:16,760 --> 00:54:19,200
Speaker 1: of the supernova. But then they fly right out through

979
00:54:19,239 --> 00:54:22,480
Speaker 1: the craziness and get to Earth before the photons do,

980
00:54:22,520 --> 00:54:24,480
Speaker 1: because the photons have to make their way sort of

981
00:54:24,520 --> 00:54:26,880
Speaker 1: through the star before they get to the surface and

982
00:54:26,920 --> 00:54:29,840
Speaker 1: can get emitted. So neutrinos are a new way to

983
00:54:30,000 --> 00:54:32,759
Speaker 1: see supernova. So now we have like new kinds of

984
00:54:32,800 --> 00:54:36,239
Speaker 1: supernova eyeballs, so that even when you're nappying, Katie, we

985
00:54:36,320 --> 00:54:39,359
Speaker 1: are watching the sky for supernovas. Thank you. That does

986
00:54:39,560 --> 00:54:42,480
Speaker 1: make me feel a little more relaxed. So I guess

987
00:54:42,680 --> 00:54:45,680
Speaker 1: you use some kind of like neutrino glasses so that

988
00:54:45,719 --> 00:54:48,800
Speaker 1: you can see these If these are not actual visible

989
00:54:48,880 --> 00:54:52,120
Speaker 1: light particles, Yeah, you cannot see new grina's very easily.

990
00:54:52,160 --> 00:54:56,399
Speaker 1: But particle physicists have neutrino experiments deep underground to try

991
00:54:56,440 --> 00:54:59,520
Speaker 1: to understand how neutrinos changed from one kind due to another,

992
00:54:59,840 --> 00:55:03,160
Speaker 1: or to do other kinds of neutrino experiments. We recently

993
00:55:03,200 --> 00:55:06,080
Speaker 1: did a whole episode about how neutrinos can teach us

994
00:55:06,120 --> 00:55:08,960
Speaker 1: about supernova, so go check that out. But one of

995
00:55:08,960 --> 00:55:11,440
Speaker 1: my favorite facts about neutrinos is that they used it

996
00:55:11,480 --> 00:55:15,120
Speaker 1: to take a picture of the Sun. Remember, neutrinos interact

997
00:55:15,239 --> 00:55:18,680
Speaker 1: very very rarely with us, but there's huge numbers of them,

998
00:55:18,680 --> 00:55:22,719
Speaker 1: Like a hundred billion neutrinos from our sun passed through

999
00:55:22,719 --> 00:55:25,399
Speaker 1: your fingernail every second. But you're lucky if you can

1000
00:55:25,440 --> 00:55:29,200
Speaker 1: even detect one in a huge specialized device. So they

1001
00:55:29,239 --> 00:55:32,200
Speaker 1: pointed this thing at the Sun for like months and

1002
00:55:32,239 --> 00:55:34,959
Speaker 1: they got a picture of the Sun in neutrinos, which

1003
00:55:34,960 --> 00:55:37,439
Speaker 1: is is kind of cool because it's like another way

1004
00:55:37,480 --> 00:55:39,560
Speaker 1: to see the Sun. I just get really excited every

1005
00:55:39,560 --> 00:55:41,960
Speaker 1: time humans build another kind of eyeball to look out

1006
00:55:41,960 --> 00:55:45,360
Speaker 1: into the universe. I'm guessing though, like neutrino glasses that

1007
00:55:45,520 --> 00:55:48,719
Speaker 1: I can wear and look and spot neutrinos myself are

1008
00:55:48,840 --> 00:55:52,839
Speaker 1: a little bit far from the market, maybe another ten

1009
00:55:52,920 --> 00:55:56,759
Speaker 1: years or so. Yeah. Currently these things have like thousands

1010
00:55:56,840 --> 00:55:59,800
Speaker 1: of tons of heavy water in them, And so unless

1011
00:55:59,800 --> 00:56:03,400
Speaker 1: you're very strong or willing to put on extremely large

1012
00:56:03,480 --> 00:56:06,080
Speaker 1: glasses and you're not going to be seeing neutrinos with

1013
00:56:06,120 --> 00:56:10,080
Speaker 1: your eyeballs. I'll work on my neck exercises. But in

1014
00:56:10,120 --> 00:56:13,719
Speaker 1: the meantime, the universe continues to churn and burn, and

1015
00:56:13,760 --> 00:56:17,600
Speaker 1: supernovas are happening out there, blowing out these incredible cosmic

1016
00:56:17,719 --> 00:56:20,480
Speaker 1: engines of the night sky. You know, we are grateful

1017
00:56:20,520 --> 00:56:23,239
Speaker 1: that stars last for as long as they do, that

1018
00:56:23,360 --> 00:56:26,800
Speaker 1: they balance on this nice edge between gravity and fusion

1019
00:56:26,920 --> 00:56:29,839
Speaker 1: for so many billion years to light up the night

1020
00:56:29,880 --> 00:56:32,920
Speaker 1: sky and to provide life here on Earth, and just

1021
00:56:32,960 --> 00:56:35,560
Speaker 1: to provide us with something nice to look at as

1022
00:56:35,600 --> 00:56:37,600
Speaker 1: we shiver in front of the fire and sip our

1023
00:56:37,680 --> 00:56:41,520
Speaker 1: hot coco on our camping trips. But eventually those stars

1024
00:56:41,560 --> 00:56:43,719
Speaker 1: do give up their life and they do go out

1025
00:56:43,760 --> 00:56:47,560
Speaker 1: in incredible cosmic explosions, which then give us another opportunity

1026
00:56:47,600 --> 00:56:51,080
Speaker 1: to learn what's going on inside the heart of those stars.

1027
00:56:51,680 --> 00:56:53,839
Speaker 1: And so the more things blow up, the more we

1028
00:56:53,920 --> 00:56:57,960
Speaker 1: learn about them. A bunch of drama queens. So if

1029
00:56:58,000 --> 00:57:00,640
Speaker 1: you're out there interested in supernova, to keep an eye

1030
00:57:00,680 --> 00:57:02,560
Speaker 1: on the night sky. You might see one with the

1031
00:57:02,640 --> 00:57:06,080
Speaker 1: naked eye. Or if you're excited about squirrels, keep watching

1032
00:57:06,080 --> 00:57:08,200
Speaker 1: to see how many acorns they eat. Maybe you'll see

1033
00:57:08,200 --> 00:57:12,280
Speaker 1: you one of those blow up. I do not endorse

1034
00:57:12,320 --> 00:57:16,600
Speaker 1: that message. Well, thanks Katie very much for joining us

1035
00:57:16,640 --> 00:57:19,840
Speaker 1: on this tour of cosmic catastrophes. Thanks for having me,

1036
00:57:20,160 --> 00:57:22,640
Speaker 1: and thank you all for listening. Tune in next time.

1037
00:57:30,520 --> 00:57:33,320
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain

1038
00:57:33,400 --> 00:57:36,400
Speaker 1: the Universe is a production of I Heart Radio. Or

1039
00:57:36,440 --> 00:57:39,360
Speaker 1: more podcast from my Heart Radio, visit the I Heart

1040
00:57:39,440 --> 00:57:43,040
Speaker 1: Radio app, Apple Podcasts, or wherever you listen to your

1041
00:57:43,080 --> 00:57:43,800
Speaker 1: favorite shows.