Speaker 1: Get in touch with technology with tech Stuff from how
Speaker 1: stuff works dot com. Hey there, and welcome to tech Stuff.
Speaker 1: I'm your host, Jonathan Strickland. I'm an executive producer and
Speaker 1: I love all things tech. And as I record this,
Speaker 1: it is the week of well Halloween in the United States.
Speaker 1: But on October Tuesday of this week eighteen, NASA chose
Speaker 1: to retire the space telescope Kepler, which had been in
Speaker 1: operation not continuously, but had been an operation since two
Speaker 1: thousand nine. I say they retired it. They didn't have
Speaker 1: much choice in the matter. The telescope had run out
Speaker 1: of fuel and could no longer hold its orientation, which
Speaker 1: is pretty important if you are using a telescope, any
Speaker 1: kind of telescope. If you've ever used any sort of
Speaker 1: magnification and you couldn't hold it's steady, you know that
Speaker 1: it's not much use. But this mission was no failure.
Speaker 1: It was actually the conclusion of a monumentally successful scientific mission.
Speaker 1: The Kepler team projected a nominal mission lifetime of three years,
Speaker 1: or maybe three and a half. The actual telescope was
Speaker 1: able to continue its original mission objectives for an additional
Speaker 1: year when it was first launched, and then Stuff started
Speaker 1: breaking down. But I'm getting ahead of myself. So let's
Speaker 1: start with the question what was Kepler's purpose? What was
Speaker 1: it built to do? The simple answer is that it
Speaker 1: was built to search the galaxy for the presence of
Speaker 1: exo planets, in other words, planets outside of our own
Speaker 1: Solar system, and that included looking for Earth like planets.
Speaker 1: Scientists had very little information to go on to make
Speaker 1: conclusions about how many stars out there might have planets.
Speaker 1: Is it common, is it infrequent? You can't really draw
Speaker 1: any other, you know, theories or or make any more
Speaker 1: hypotheses until you get more information about how frequently planets
Speaker 1: are a thing out there. And that's before you get
Speaker 1: to the question of how many planets might be similar
Speaker 1: to Earth, or, even more importantly, in our our grand
Speaker 1: scheme of things, how many of those planets might be
Speaker 1: in an orbit around their respective stars in what we
Speaker 1: would call the h Z or habitable zone. So the
Speaker 1: habitable zone, it's pretty self explanatory. It's the region surrounding
Speaker 1: a star in which water could exist in its liquid
Speaker 1: state if it were on a planet. So there's not
Speaker 1: a single range we can give to describe the habitable zone. Right,
Speaker 1: I can't just tell you it's x many millions of
Speaker 1: miles away, And the reason for that is because there
Speaker 1: are different kinds of stars. So to determine the habitable
Speaker 1: zone of a star, first you have to ask yourself
Speaker 1: the question, is this star old enough that any planets
Speaker 1: that might be orbiting it would have been around long
Speaker 1: enough to have time necessary for life to develop, because
Speaker 1: it would probably take billions of years, So you want
Speaker 1: to make sure that the solar system you're looking at
Speaker 1: is actually old enough for that to have been a possibility.
Speaker 1: On a similar note, the size of the star matters.
Speaker 1: Larger stars have shorter lifespans than smaller stars. Generally speaking,
Speaker 1: that's because stars with greater mass will burn through their
Speaker 1: fuel more quickly than smaller stars. The process of fusion
Speaker 1: will be at a much greater rate for a larger
Speaker 1: star than it is for a smaller star. So if
Speaker 1: you have a really big star, it may only live
Speaker 1: to be a few million years old before it collapses
Speaker 1: and explodes in a supernova. Now I know, a few
Speaker 1: million years it's a long time for humans, but for
Speaker 1: stars most stars, like the smaller ones, that's not long
Speaker 1: at all. A star of the size of our sun
Speaker 1: could stick around for maybe ten billion years the sun.
Speaker 1: Our sun is currently around four point six billion years old,
Speaker 1: so we got a bit. We got a minute or
Speaker 1: two before it burns out, and honestly, before it would
Speaker 1: burn out, there would be other things going on that
Speaker 1: would be of immediate concern to us. But yeah, we
Speaker 1: got billions of years before that happens. So really, big
Speaker 1: stars are not good candidates for finding planets that might
Speaker 1: have life on them, just because they probably haven't been
Speaker 1: around long enough for life to develop. So small stars, well,
Speaker 1: that gets tricky too if the star is too small.
Speaker 1: The habitable zone overlaps a region wherein an orbiting planet
Speaker 1: would be entitled lock with its star. So title lock
Speaker 1: means the same side of the planet would always face
Speaker 1: the star, and the opposite side would always face away
Speaker 1: from the star, So one side of the planet would
Speaker 1: always be bathed in starlight. The other side of the
Speaker 1: planet would always be dark. So the side facing the
Speaker 1: star would be too warm for liquid water or to exist.
Speaker 1: Most likely it would be it would just be too hot,
Speaker 1: it would evaporate out and boil off. There's nothing out
Speaker 1: there to say that water is absolutely necessary for all
Speaker 1: kinds of life. We're going from a sample size of
Speaker 1: one planet that we know of that has life on it,
Speaker 1: So we're having to make a lot of assumptions here
Speaker 1: that could ultimately be wrong. But assuming water is necessary,
Speaker 1: very small stars and very big stars are not really
Speaker 1: good candidates for planets that may support life. Now, there
Speaker 1: are a lot of different ways to classify stars, but
Speaker 1: the modern classification system is called the Morgan Keenan system
Speaker 1: and that divides stars into spectral classes, which sources stars
Speaker 1: into categories based on the spectrum of electromagnetic radiation that
Speaker 1: the star emits. Using something like a prism, you can
Speaker 1: look at this spectrum of visible light. So prisms break
Speaker 1: up visible light into the different colors that you would see.
Speaker 1: You know, you get the visible light coming at you
Speaker 1: use a prism, and then you can actually see uh
Speaker 1: the spectrum, the full spectrum of light. And this kind
Speaker 1: of approach, you would have spectral lines interspersed through a
Speaker 1: range of colors. It would be like little black bars
Speaker 1: that would be throughout the spectrum. In eruptions in the spectrum,
Speaker 1: if you if you will, those lines indicate the abundance
Speaker 1: of certain elements and the type of element will UH
Speaker 1: you can determine what type of element is by where
Speaker 1: on the spectrum. Those spectral lines are mostly However, the
Speaker 1: spectral lines correspond with the stars surface temperature, and the
Speaker 1: classification of stars from hottest to coolest goes like this,
Speaker 1: oh B A, F G K, M. Some people use
Speaker 1: a handy mnemonic device to remember that, like, oh be
Speaker 1: a fine guy, kiss me kind of sweet. If you
Speaker 1: think about it, oh BI and A stars typically burn
Speaker 1: out before the time we would expect it would take
Speaker 1: for life to develop on orbiting planets, So those are
Speaker 1: your larger, hotter stars. That leaves us with F, G, K,
Speaker 1: and M stars as candidates for stars that might host
Speaker 1: planets that could potentially support life. For low mass cooler stars,
Speaker 1: the habitable zone will be closer in than if the
Speaker 1: star were larger and hotter. So, in other words, you
Speaker 1: have to have that perfect temperature or range of temperatures
Speaker 1: for water to exist in liquid form on the surface
Speaker 1: of the planet. So if a planet is too close
Speaker 1: to its star, it's possibly going to be tidally locked,
Speaker 1: and it's also gonna be too hot. If it's too
Speaker 1: far away, it's going to be too cold. So a
Speaker 1: planet must be in orbit around its respective star in
Speaker 1: such a way that it is not in title lock.
Speaker 1: It's not too close, it's not too far, it's not
Speaker 1: too hot, it's not too cold. And for that reason
Speaker 1: a lot of people have also started calling the habitable
Speaker 1: zone the Goldilocks zone because it's just right. Okay, So
Speaker 1: we have some ideas about planets that could in theory
Speaker 1: support life if they fell into the habitable zone. It
Speaker 1: doesn't mean that they definitely have life on them. We
Speaker 1: cannot make that determination. All we could say is, well,
Speaker 1: in theory, water could exist on that planet, and that's
Speaker 1: the best we can say. So that's one thing, But
Speaker 1: detecting planets in the first place is actually something else.
Speaker 1: Just because we could say, in theory, if a planet
Speaker 1: were to exist within this band of ranges around its star,
Speaker 1: it might be able to support life, doesn't mean we've
Speaker 1: actually found any planets, right. We have to figure out
Speaker 1: how to do that. So we have really powerful telescopes
Speaker 1: here on Earth, but that's not really gonna cut it.
Speaker 1: Even with a telescope that has an enormous aperture several
Speaker 1: meters across, the conditions are such that we're not going
Speaker 1: to be able to directly image planets. They're just the
Speaker 1: star are too far away. The distance between us and
Speaker 1: nearby stars is enormous light years, and comparatively speaking, the
Speaker 1: distance between a planet and its host star is nothing
Speaker 1: at all. Right, a few million miles is nothing compared
Speaker 1: to light years. So the light reflecting off a planet
Speaker 1: would also be much much, much much less bright than
Speaker 1: the light coming off of a star, like maybe a
Speaker 1: billion times less bright. So if we're looking at a
Speaker 1: star of comparable size and brightness to our Sun, then
Speaker 1: the planet that orbits it it will end up reflecting
Speaker 1: some light off of it, but it will be a
Speaker 1: tiny fraction of the light that's coming from the Sun.
Speaker 1: So our earth based telescopes would blur this light together
Speaker 1: due to diffraction, and we wouldn't really be able to
Speaker 1: tell the difference. We wouldn't be able to distinguish the
Speaker 1: planet from the star, so direct observation with Earth based
Speaker 1: telescopes is a non starter. However, we could look at
Speaker 1: indirect ways to observe the presence of a planet or
Speaker 1: to uh too, guess whether or not a planet is there.
Speaker 1: So stars have a gravitational poll on their planets, but
Speaker 1: planets also exert a gravitational poll on their host stars,
Speaker 1: and as planets move through their orbits around the star,
Speaker 1: they caused the star to wobble a little bit. The
Speaker 1: center of this gravitational poll is likely within the the
Speaker 1: diameter of the star itself, but it's not right at
Speaker 1: the center of the star. So the star kind of
Speaker 1: wiggles a little bit as the planets orbit around it.
Speaker 1: So if you are able to detect this wobble, if
Speaker 1: you're able to see it, then you could uh then
Speaker 1: deduce that there's something in orbit around that star. We've
Speaker 1: used this methodology to detect binary stars that were too
Speaker 1: close together for our Earth based telescopes to differentiate between
Speaker 1: the too. We call this the astrometric method of detecting
Speaker 1: binary stars. But planets are much smaller than stars, so
Speaker 1: the wobbles that are produced by planets are much smaller
Speaker 1: than would be produced by binary star systems AUH. It
Speaker 1: is the oldest methodology for searching for exoplanets, but for
Speaker 1: many years no one could confirm that any wobbles they
Speaker 1: were seeing actually meant there were planets in orbit around
Speaker 1: those stars. That changed in the era of space telescopes.
Speaker 1: That changed in the era of more advanced telescopes in
Speaker 1: the nineties, but let's set that aside for now. The
Speaker 1: Kepler telescope would be powerful enough to use an alternative
Speaker 1: method to detect exo planets. This is the so called
Speaker 1: transit method, and the transit method looks for indications that
Speaker 1: a planet is moving between a star and Earth. That is,
Speaker 1: it is transitting across the face of the star from
Speaker 1: our perspective. Now, we would detect this by measure ring
Speaker 1: the amount of light coming from the star. The planet
Speaker 1: would still be too far away and too small for
Speaker 1: us to see. It's not like we would see a
Speaker 1: tiny black dot moving across the star. But what we
Speaker 1: could do is measure exactly how much light are we
Speaker 1: receiving from that star. And if we noticed that there
Speaker 1: was a dip in the intensity of that light, it
Speaker 1: would indicate that something had passed between the star and us,
Speaker 1: that something had blocked some of that light from getting
Speaker 1: at us. A dip that happens with regularity would indicate
Speaker 1: that there is a planet in orbit around that star.
Speaker 1: That if we're seeing every so often that little dip happened,
Speaker 1: it would tell us, all right, there's something that's orbiting
Speaker 1: the star. And every time it comes across, that's when
Speaker 1: we see the dip, and that's why there's this gap
Speaker 1: between dips. If it's regular, that is, if it were irregular,
Speaker 1: we wouldn't necessarily know what the heck is going on,
Speaker 1: unless maybe it was multiple planets that were in orbit
Speaker 1: around the star. It would, however, require a very powerful
Speaker 1: and very precise telescope, and not only that, it would
Speaker 1: also require the planet's orbit around its star to be
Speaker 1: in an alignment so it would actually pass between the
Speaker 1: star and us. In other words, it would need to
Speaker 1: be at the right angle. So if the orbit was
Speaker 1: at a tilt from our perspective, if it were orbiting
Speaker 1: its star, but in such a way that its pathway
Speaker 1: did not cross between us and the star, we wouldn't
Speaker 1: see any indication of it because the light woulden't dim,
Speaker 1: you know, the light would still be coming straight at us.
Speaker 1: So it requires a couple of different things for for
Speaker 1: us to even pick it up. NASA started looking into
Speaker 1: the possibility of using the transit method to detect planets
Speaker 1: in the nineteen eighties, and one early step was a
Speaker 1: workshop at the NASA Aims Research Center in high precision photometry.
Speaker 1: Photometry is the science of the measurement of intensity of light.
Speaker 1: That's what I was talking about earlier, about measuring how
Speaker 1: much light is coming to you. That's using photometry. That
Speaker 1: science has been around for a bit. And you know,
Speaker 1: it's obvious that not everything that emits light does so
Speaker 1: at the same intensity. Right, Some things are brighter than others,
Speaker 1: some things are dimmer than others. Light isn't just on
Speaker 1: or off. There's a magnitude associated with it. Quantifying magnitude
Speaker 1: was really tricky. I have more to say about photometry
Speaker 1: and its history in just a second, but first let's
Speaker 1: take a quick break to thank our sponsor. Okay, we're
Speaker 1: back now. One day I'm going to have to do
Speaker 1: a full episode about photometry. The history of photometry is fascinating.
Speaker 1: It actually it dates all the way back to the
Speaker 1: ancient Greeks and Romans. But obviously, by the time we're
Speaker 1: talking about the the events that would lead into the
Speaker 1: development of the Kepler telescope, NASA was looking into something
Speaker 1: a little more sophisticated than what the ancients were capable
Speaker 1: of doing. Now, during the workshop on photometry, the group
Speaker 1: had several goals they wanted to achieve. One was determine
Speaker 1: which astronomical problems would benefit by increased photometric precision. So
Speaker 1: we've got this technology, if we make it better, what
Speaker 1: could we use it to do? What would it be
Speaker 1: good for? Another was to get a handle on what
Speaker 1: the current level of precision was with the latest equipment,
Speaker 1: So not just what would it be good for if
Speaker 1: we made it better, but how good is it right now?
Speaker 1: Another goal was to identify any of the things that
Speaker 1: would limit the precision of photometry, so what stands in
Speaker 1: our way of making this technology better? And finally, the
Speaker 1: last goal was to make recommendations to overcome or sidestep
Speaker 1: any of those limitations. The workshop was considered a success,
Speaker 1: and that led to a second workshop that was held
Speaker 1: in NASA Commission to study to determine if a multi
Speaker 1: channel photometer built on silicon photo diodes would be practical,
Speaker 1: and the researchers found that such photometers were incredibly precise,
Speaker 1: but they would also have to be super cooled down
Speaker 1: to less than negative one degrees celsius or negative three
Speaker 1: degrees fahrenheit, the temperature of liquid nitrogen. In other words, Now,
Speaker 1: since I'm gonna do an episode about photometry in the future,
Speaker 1: I'm going to skip a deep explanation of how those
Speaker 1: devices work for now. Just know that they are all
Speaker 1: about quantifying the intensity of light that is hitting them.
Speaker 1: So let's go back to our history lesson leading up
Speaker 1: to the Kepler telescope. In the early NASA officials were
Speaker 1: considering a suite of new missions for the organization to pursue.
Speaker 1: Some of them were aimed at getting a more comprehensive
Speaker 1: understanding of our own Solar system, but some were meant
Speaker 1: to search for planets outside of our immediate neighborhood. One
Speaker 1: of those proposed missions got the name free SIP or
Speaker 1: f R E s I P, which stood for Frequency
Speaker 1: of Earth size Inner Planets. Like all the proposed missions,
Speaker 1: the team had to outline the scientific and technical requirements
Speaker 1: to complete mission objectives, as well as how much they
Speaker 1: estimated it would cost, and a proposed schedule and management plan.
Speaker 1: Free SIP would land on the chopping block. It would
Speaker 1: not make it through in that initial round, and in
Speaker 1: nine two there just wasn't sufficient evidence that the technical
Speaker 1: equipment would be sensitive enough to pick up the transit
Speaker 1: of a distant planet and yet also be able to
Speaker 1: filter out noise. So what NASA HQ was saying was
Speaker 1: this is it's not that your idea doesn't have merit,
Speaker 1: it's that we cannot be certain that the equipment you
Speaker 1: would use would actually achieve the goals, and we don't
Speaker 1: want to spend millions of dollars on something that ultimately
Speaker 1: doesn't work. The scientific community still felt that the objective
Speaker 1: was worth pursuing, so in nineteen scientists organized another workshop
Speaker 1: called Astrophysical Science with a space born photometric telescope in
Speaker 1: mountain View, California. More specifically, not just mountain View, California,
Speaker 1: this event took place at SETI Headquarters cet IS the
Speaker 1: Search for Extra Terrestrial Intelligence. Also in NASA announced the
Speaker 1: initiation of Discovery class missions. Now that's a category of
Speaker 1: missions that are supposed to be complementary to the larger
Speaker 1: missions that NASA pursus. So these are supposed to be
Speaker 1: smaller and therefore also less expensive than the bigger missions.
Speaker 1: The Frecept team would resubmit their proposal as a Discovery
Speaker 1: class mission, but then NASA ultimately rejected that second attempt,
Speaker 1: and the reason they gave was that they felt that
Speaker 1: the mission as described would be too expensive to qualify
Speaker 1: as a Discovery class mission. In a team of scientists
Speaker 1: at the University of Geneva announced that they had discovered
Speaker 1: an exo planet in the constellation Pegasus. This exo and
Speaker 1: it got the designation fifty one pegasie B. The team
Speaker 1: had used the so called Wobble method radial velocity method
Speaker 1: to detect this planet, and that helped fuel interest in
Speaker 1: the search for more exoplanets in the free SIP team
Speaker 1: had yet another chance to propose a flight mission, and
Speaker 1: this time they made a really big adjustment to their proposal.
Speaker 1: Actually they made two big adjustments. It's just that one
Speaker 1: of them was perhaps more important and more key to
Speaker 1: getting approval, and that was changing the parameters of the mission.
Speaker 1: The original proposal required putting a spacecraft in a lagrange orbit.
Speaker 1: Now that's a position in space where the combined gravitational
Speaker 1: forces of two large bodies equal the centrivigal force of
Speaker 1: a body that's in that position between the two or
Speaker 1: around the two. So the two large bodies in the
Speaker 1: case that we care about are the Earth and the Sun.
Speaker 1: So there are five lagrange points that are in that
Speaker 1: vicinity around the Sun and Earth. They have designations that
Speaker 1: go from L one up to L five, So L
Speaker 1: one lagrange orbit is at a point between Earth and
Speaker 1: the Sun. It's much closer to the Earth than the
Speaker 1: Sun because gravity depends upon mass and distance, and the
Speaker 1: Earth is much less massive than the Sun, so you
Speaker 1: need to get closer if you want to have all
Speaker 1: that stuff kind of balance out. L two is actually
Speaker 1: located behind Earth with respect to the Sun, so in
Speaker 1: an orbit that's uh, that's further out from the Sun
Speaker 1: than Earth is. L three is actually on the opposite
Speaker 1: side of the Sun from where the Earth is. L
Speaker 1: four and L five are in effect at an orbit
Speaker 1: sixty degrees ahead and sixty degrees behind the Earth, respectively.
Speaker 1: In its orbit. Now, a satellite at L one would
Speaker 1: have an unobstructed view of the Sun, and that's why
Speaker 1: we put the solar in Heliospheric Observatory there. A satellite
Speaker 1: at ALL two would have a view of deep space,
Speaker 1: and it would be shaded from the Sun because it
Speaker 1: would be in the shadow of Earth. That's where the
Speaker 1: James Webb Space Telescope will eventually be. These orbits require
Speaker 1: a lot of adjustments to keep a satellite stable, otherwise
Speaker 1: they would drift out of orbit and move into a
Speaker 1: collision course with a celestial body like the Sun, for example,
Speaker 1: Moving a telescope into one of those orbits and keeping
Speaker 1: it there would have required a lot more fuel and
Speaker 1: thus added expense to the mission. So this new proposal
Speaker 1: for what was originally called Free SIP suggested putting the
Speaker 1: telescope in a normal solar or orbit rather than on
Speaker 1: a grange orbit, and that brought the cost down significantly,
Speaker 1: and the mission also got a new name. This was
Speaker 1: the second big change, and that new name was Kepler,
Speaker 1: after Johannes Kepler, the seventeenth century German astronomer. The mission
Speaker 1: still did not get greenlit at that time, however, then
Speaker 1: they tried again and they got turned down again. The
Speaker 1: team were told they needed to demonstrate the photometry system
Speaker 1: they had in mind would actually be sufficient to pick
Speaker 1: up the transit of a planet across its star. So
Speaker 1: they built a testing facility at the Aimes Research Center
Speaker 1: and they began running more than a hundred fifty simulations
Speaker 1: to prove that their system would actually work. In two
Speaker 1: thousand one, NASA officials finally gave approval to Kepler. This
Speaker 1: was the fifth proposal for that mission, and it was
Speaker 1: designated as the tenth Discovery Class mission. For nearly a decade,
Speaker 1: engineers and scientists got to work building the actual telescope.
Speaker 1: I'll talk more about how it worked in just a moment,
Speaker 1: but the telescope launched on March sixth, two thousand nine.
Speaker 1: It was on top of a three stage Delta two
Speaker 1: rocket that's what was used as the launch vehicle, and
Speaker 1: more than a month would go by once it reached
Speaker 1: its orbit before it would take the first image of
Speaker 1: a small patch of sky. It was a small patch
Speaker 1: of sky which was occupied by part of the constellation Sicknus,
Speaker 1: the Swan and Lyra or a liar, also known as
Speaker 1: the harp. There's a term for this moment when a
Speaker 1: space telescope like this sends back its first image, and
Speaker 1: it's called first light, which I think is kind of cool. Also,
Speaker 1: it had the equivalent of a lens cap. It's a
Speaker 1: a very very large lens cap because the telescope has
Speaker 1: quite a large opening at one end, but that had
Speaker 1: to be jettisoned first before any images could be sent back. Obviously,
Speaker 1: otherwise you just get if you've ever taken a picture
Speaker 1: with a camera that still had a lens cap on,
Speaker 1: you know, what you get, you get pitch black darkness.
Speaker 1: That same little small patch of sky. By the way,
Speaker 1: while it is a tiny, tiny portion of the overall
Speaker 1: night sky, it's home to around four and a half
Speaker 1: million stars. Kepler's job was to monitor around a hundred
Speaker 1: seventy thousand of the stars simultaneously, So its job was
Speaker 1: just to monitor the brightness of those stars and look
Speaker 1: for tiny variations in their luminosity, regular ones, periodic dips
Speaker 1: in their luminosity, which would indicate an exoplanet in transit.
Speaker 1: On January four, the Kepler team announced that the telescope
Speaker 1: had detected five planets. They had gone through the data
Speaker 1: and they had found enough convincing data to say that
Speaker 1: in those five cases, they're certainly appeared to be planets
Speaker 1: in orbit around their respective stars, and they had exciting
Speaker 1: names like Kepler four B, Kepler five B, Kepler six B,
Speaker 1: Kepler seven B, and Kepler eight B. They fell into
Speaker 1: a class of planets called hot jupiters. Now, these are
Speaker 1: planets that are of a similar size to Jupiter in
Speaker 1: our Solar system. That's the biggest Planet's got a diameter
Speaker 1: that's eleven times greater than Earth's. Technically you could fit
Speaker 1: about one thousand three earths inside a single jupiter. So
Speaker 1: what makes them hot, Well, it's that these planets are
Speaker 1: relatively close to their parents stars. The orbits are very short.
Speaker 1: Compared to an Earth year, a year on one of
Speaker 1: those planets might only take three or four Earth days.
Speaker 1: So every imagine that every three or four days you've
Speaker 1: gone through an entire year. That is uh the equivalent
Speaker 1: of these planets years um. It made it easier to
Speaker 1: detect because they were big planets, so they had a
Speaker 1: big impact on the amount of light that was hitting
Speaker 1: the Kepler telescope, so you could see the indication very clearly.
Speaker 1: And because they were so close to their parents stars,
Speaker 1: it happened so frequently that you could keep that you
Speaker 1: could actually make predictions of when you would see the
Speaker 1: next dip, and if in fact a dip occurred when
Speaker 1: you predicted it, it would be a strong support that yes,
Speaker 1: there is a very large planet that's in orbit around
Speaker 1: that star. So the telescope was very successful. It was
Speaker 1: indicating that there were bodies or in orbit around other
Speaker 1: stars and other solar systems. It wasn't measuring the wobble
Speaker 1: is just measuring the light and it was showing that
Speaker 1: this method actually had a lot of validity to it. Now,
Speaker 1: in our next segment, I will go into a little
Speaker 1: bit about how Kepler actually worked and what else it
Speaker 1: discovered in its lifetime out in space. But first let's
Speaker 1: take a quick break to thank our sponsor. The Kepler
Speaker 1: telescope looked like a cylinder, probably about twice as tall
Speaker 1: as your typical person, so fairly large telescope. It had
Speaker 1: solar panels along the sun facing side of the satellite,
Speaker 1: so it would generate electricity that would be used to
Speaker 1: power various parts of the telescope. It also had an
Speaker 1: angled opening. It was essentially a sunshade that would the
Speaker 1: Sun's light from interfering with the light the telescope was
Speaker 1: trying to pick up from distant stars. You didn't want
Speaker 1: to have interference there, otherwise the sensors inside the telescope
Speaker 1: would just be registering the Sun rather than the stars
Speaker 1: it was looking for. To keep Kepler pointed at the
Speaker 1: right patch of sky, the telescope had four reaction wheels.
Speaker 1: I guess technically it still has four reaction wheels, just
Speaker 1: there's nothing to power them anymore. Uh. These were motorized
Speaker 1: components that could cause Kepler to move in the opposite
Speaker 1: direction of the spinning of each wheel, and the wheels
Speaker 1: could spend really fast, like around a thousand to four
Speaker 1: thousand revolutions per minute. The wheels were a known point
Speaker 1: of vulnerability as well. The the group knew that the
Speaker 1: wheels had failed on other spacecraft. After a while, but
Speaker 1: they also realized that they needed components that would help
Speaker 1: keep the budget down for Kepler, and eventually, once it
Speaker 1: got to the point where they were really worried about
Speaker 1: their reliability, it was a bit too late, so the
Speaker 1: vulnerability would become a true thorn in the side of
Speaker 1: the group in two thousand twelve. That's when one of
Speaker 1: the four wheels failed. A second wheel would fail in
Speaker 1: two thousand thirteen, and the kepler needed at least three
Speaker 1: working wheels to maintain its orientation that way, So in
Speaker 1: two thousand thirteen, the primary mission for Kepler came to
Speaker 1: an end. The aperture on the telescope measured nearly a
Speaker 1: meter in diameter. The light detection comes from an array
Speaker 1: of forty two camera sensors, which collectively acted like a
Speaker 1: ninety five megapixel camera. Now specifically, the camera sensors were
Speaker 1: c c d s, or charge couple devices. Each one
Speaker 1: measured fifty by twenty five millimeters in size, and each
Speaker 1: one had a resolution of twenty two hundred by one thousand,
Speaker 1: twenty four pixels. The c c d s wouldn't record
Speaker 1: information from stars below a certain lumina that would limit
Speaker 1: the amount of data being fed back to NASA. Essentially,
Speaker 1: they were saying, you know, some of these stars are
Speaker 1: so faint that it doesn't make sense for us to
Speaker 1: track them because we're not getting enough data to be
Speaker 1: able to reliably say, oh, this represents a depth in
Speaker 1: that light. On January ten, two thousand eleven, just a
Speaker 1: bit more than a year after NASA had announced the
Speaker 1: first five planets discovered by Kepler, the agency had a
Speaker 1: new announcement, which was that the telescope had discovered the
Speaker 1: first unquestionably rocky planet orbiting a distant star. This one
Speaker 1: became a Kepler ten B. Later that year, NASA would
Speaker 1: reveal that Kepler had found a planet that the team
Speaker 1: would designate Kepler sixteen B. This one was special, and
Speaker 1: that it was a planet in a double star system,
Speaker 1: which always makes me think of tattooing in the Star
Speaker 1: Wars series with the two sons at sunset, and at
Speaker 1: the tail end of two thousand eleven, NASA announced Kepler
Speaker 1: twenty two B. That was the first plant to be
Speaker 1: found in the habitable zone around its respective star, and
Speaker 1: it has a diameter that's about twice the size of Earth's,
Speaker 1: so it's a bigger planet than ours is. In two
Speaker 1: thousand thirteen, after the second reaction wheel failure, the team
Speaker 1: worked had to work on coming up with a way
Speaker 1: to still use the telescope without being able to use
Speaker 1: the intended method to keep its orientation to make sure
Speaker 1: it was pointed in the right way. Meanwhile, researchers were
Speaker 1: discovering more exoplanets as they were pouring over all the
Speaker 1: data that Kepler had gathered in its operations, and that
Speaker 1: would continue on for a couple of years. Just because
Speaker 1: the telescope wasn't in current operation didn't mean it wasn't
Speaker 1: providing really useful data for people to pursue, because they
Speaker 1: could actually go through all the stuff that already been
Speaker 1: collected and look for more signs of it. In May
Speaker 1: two thousand fourteen, the Kepler Telescope would start a new
Speaker 1: mission called K two. In this mission. The team would
Speaker 1: rely upon sunlight, which actually does exert pressure. That's the
Speaker 1: actually the working principle behind things like solar sales, and
Speaker 1: they used the sunlight to help keep the Kepler pointed
Speaker 1: in the right direction. Now, that would mean the telescope
Speaker 1: would have to look at around four different sections of
Speaker 1: sky every year, every three months or so, it would
Speaker 1: change its orientation just because they could not keep it
Speaker 1: pointed at the exact same patch all year round while
Speaker 1: relying upon sunlight to study it. But it did mean
Speaker 1: that the telescope could keep operating. It just wouldn't look
Speaker 1: at the same thousand stars all year round. Instead, it
Speaker 1: was more like half a million stars in total throughout
Speaker 1: the year. But then keep in mind if you're looking
Speaker 1: at different patches of stars every three months or so.
Speaker 1: If you aren't, if it's not timed out the same
Speaker 1: way as a planet transitting its own parents star, you
Speaker 1: don't get any more data from that, right you may
Speaker 1: it may be that you look away just as something
Speaker 1: interesting happens, which is the story of my life. I
Speaker 1: should just title my autobiography I wasn't looking. Over the years,
Speaker 1: the information from Kepler kept providing researchers with more evidence
Speaker 1: of exoplanets and other interesting phenomena. So in data suggested
Speaker 1: that a rocky planet orbiting a white dwarf star was
Speaker 1: actually being pulled apart as its solar system was kind
Speaker 1: of dying. In two thousand sixteen, some interesting information showed
Speaker 1: odd fluctuations in a particular stars brightness, which led some
Speaker 1: people to theorize that perhaps some alien civilization had built
Speaker 1: a mega structure around that star. It was far more
Speaker 1: likely than the fluctuations were caused by a dust cloud,
Speaker 1: but it was still a super cool thing. In the
Speaker 1: spring of twenty six NASA announced that the team had
Speaker 1: found one thousand, two hundred new exo planet's after reviewing
Speaker 1: Kepler data, And that was a huge announcement, and all
Speaker 1: of these were from that original mission of Kepler, not
Speaker 1: the K two mission. This was still from its first run.
Speaker 1: In twenty seventeen, NASA producer report that stated Kepler had
Speaker 1: detected four thousand, thirty four potential planets in its original mission,
Speaker 1: with two thousand, three hundred thirty five planets confirmed now. Originally,
Speaker 1: the team estimated that about thirty of those planets were
Speaker 1: likely close to Earth's size and were of a rocky nature.
Speaker 1: Further examination, however, tempered our expectations a bit reduced that
Speaker 1: number somewhere down between two and twelve. In two thousand eighteen,
Speaker 1: the power of crowdsourcing in science was proven again when
Speaker 1: an Australian car mechanic discovered a planet system that had
Speaker 1: at least four Neptune sized planets in it. He had
Speaker 1: taken the data from the K two mission and had
Speaker 1: gone through it meticulously. NASA would end up confirming his
Speaker 1: find and also the scientists who were looking into it
Speaker 1: discovered that the planet actually had a fifth or the
Speaker 1: star rather had a fifth planet in its system. So
Speaker 1: cool stuff. On April eighteen, two eighteen, the Transiting Exo
Speaker 1: Planet Survey Satellite or Tests launched into orbit. This is
Speaker 1: Kepler's successor. It's going to be looking for planets using
Speaker 1: the transit method, much like Kepler did. On October eighteen,
Speaker 1: NASA essentially pulled the plug on Kepler. Now it could
Speaker 1: no longer operate as it run out of fuel that
Speaker 1: needed to help stabilize its position. It was too wobbly.
Speaker 1: It was just not going to provide reliable information. So
Speaker 1: it will remain in its orbit. It's safely away from Earth,
Speaker 1: but it will be defunct. Out in space, tests, which
Speaker 1: is more powerful than Kepler was, is expected to detect
Speaker 1: perhaps more than twenty thousand new exo planets, and Kepler
Speaker 1: has given us a lot to think about. Before Kepler,
Speaker 1: we didn't really know how common exo planets were. It
Speaker 1: could be that they were really really rare. But Kepler
Speaker 1: discovered hundreds of multiplanet systems in a few small patches
Speaker 1: of sky. So extrapolating from that information, we can estimate
Speaker 1: that there are possibly hundreds of billions of planets in
Speaker 1: our galaxy alone. Though to be fair, we don't actually
Speaker 1: know how many stars are in the Milky Way Galaxy,
Speaker 1: we can estimate it. We think it's somewhere between one
Speaker 1: billion and four hundred billion. So even if we are
Speaker 1: being conservative we say a hundred billion, And even if
Speaker 1: we say that only a tiny fraction of the exo
Speaker 1: planets out there are earth like and in a habitable
Speaker 1: zone around the respective stars, you're still talking about hundreds
Speaker 1: of millions of planets that might possibly support life in
Speaker 1: the Milky Way galaxy. Future telescopes will give us more
Speaker 1: information about those exo planets. Visiting one, however, is going
Speaker 1: to take a lot longer. The closest exoplanet orbiting in
Speaker 1: the habitable zone of its star is Proxima Centauri B.
Speaker 1: That's orbiting the red dwarf star Proxima Centauri. And just
Speaker 1: to be clear, Kepler did not discover Proxima B. That
Speaker 1: planet was discovered by the European Southern Observatory using the
Speaker 1: radial velocity method, you know, the good old Wobbli method.
Speaker 1: That star, however, is the closest star to our Sun,
Speaker 1: but closest is a relative term. It's still four point
Speaker 1: two light years away. Now, that means it takes more
Speaker 1: than four years for light from that star to reach us.
Speaker 1: The spacecraft we have designed so far in the history
Speaker 1: of space travel, in in all of human history, they
Speaker 1: travel significantly slower than the speed of light. And obviously
Speaker 1: we can't get matter up to the speed of light
Speaker 1: because matter has mass, So getting to this destination would
Speaker 1: take a really long time. However, one company called Breakthrough
Speaker 1: Initiatives has proposed a plan that would do it sort of.
Speaker 1: They plan to launch small, unmanned spacecraft that they call
Speaker 1: star chips. These tiny spacecraft would use light sales for propulsion,
Speaker 1: so light sales or solar sales use pressure from photons.
Speaker 1: Photons don't have a mass, but they do have a
Speaker 1: relativistic mass, which means they have momentum, which means when
Speaker 1: they hit against something, they transfer momentum to it. So
Speaker 1: you can actually accelerate a spacecraft by having photons bounce
Speaker 1: off a solar sale. It does take a while to
Speaker 1: get up to a pretty fast speed, but you're under
Speaker 1: constant acceleration, so while the acceleration isn't so dramatic, you're
Speaker 1: not going like zero two, you know, point to five
Speaker 1: the speed of light in in five seconds. It takes
Speaker 1: a long time to get up to speed, but according
Speaker 1: to the company, the StarCraft they have designed will eventually
Speaker 1: reach a top speed of about twenty that of the
Speaker 1: speed of light, so they would get to Proxima B
Speaker 1: in around twenty years or so. Then you have to
Speaker 1: tack on another four years for the information they were
Speaker 1: sending back to get to us, So twenty four twenty
Speaker 1: five years from the time that those are launched and
Speaker 1: they start heading toward Proxima B before we would find
Speaker 1: anything out about it. But still pretty exciting, and the
Speaker 1: search for exoplants continues Kepler is done, but it has
Speaker 1: served us well. It has given us a lot more
Speaker 1: information and told us that planets are way more plentiful
Speaker 1: than we might have hoped. Whether or not planets in
Speaker 1: the habitable zone are more plentiful, that still remains to
Speaker 1: be seen. We're gonna have to really do a careful
Speaker 1: study with using multiple lines of inquiry to make that determination.
Speaker 1: But it's really exciting stuff. I hope you guys enjoyed
Speaker 1: this episode. If you have any suggestions for me, any
Speaker 1: questions or anything like that, you can go on over
Speaker 1: to tech Stuff podcast dot com. That's the website for
Speaker 1: the series. You can learn more about the show there,
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