WEBVTT - What Is The Dwarf Planet Ceres?

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<v Speaker 1>Welcome to brain Stuff from How Stuff Works. Hi, I'm

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<v Speaker 1>Christian Seger, and this is brain Stuff. If you follow

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<v Speaker 1>the latest in space gossip, you might have heard about

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<v Speaker 1>a little rendezvous between a NASA probe called Dawn and

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<v Speaker 1>an object in space known as the dwarf planet Series.

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<v Speaker 1>This meet up is exciting news for space fanatics. But

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<v Speaker 1>if you don't know what Series is, and at this

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<v Speaker 1>point you're too afraid to ask, well, we are here

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<v Speaker 1>to lay down the facts you need to know. Series

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<v Speaker 1>first came to human attention when the Italian astronomer Giuseppe

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<v Speaker 1>Piazzi spied a moving point of light from the Palermo

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<v Speaker 1>Observatory on New Year's Day in eighteen o one. Yeah,

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<v Speaker 1>eighteen o one. That means Series was actually discovered almost

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<v Speaker 1>a hundred and thirty years before the former planet and

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<v Speaker 1>now fellow dwarf planet, Pluto. Piazzi correctly deduced that the

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<v Speaker 1>object was somewhere between the orbits of Mars and Jupiter.

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<v Speaker 1>In reality, that zone contains the thing we now know

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<v Speaker 1>as the asteroid Belt, a loose ring of rocky objects,

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<v Speaker 1>of which Series is the largest. Piazzi named this new

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<v Speaker 1>space dot after the Roman deity Series the goddess of

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<v Speaker 1>grain and nutritious food crops. Historically, astronomers have gone back

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<v Speaker 1>and forth about the status of this object. Piazzi himself

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<v Speaker 1>initially thought it might be a comet. It has also

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<v Speaker 1>been known as a planet and as an asteroid, but

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<v Speaker 1>today astronomers classify Series as a dwarf planet. So you

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<v Speaker 1>might be wondering what makes a dwarf planet different from,

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<v Speaker 1>you know, a regular planet or a comet or an asteroid. Well,

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<v Speaker 1>according to the International Astronomical Union, a dwarf planet is

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<v Speaker 1>any object that meets the following four criteria. First, it

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<v Speaker 1>goes around the Sun. Okay, that's a check for Series. Two,

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<v Speaker 1>it's not a moon. Another check for Series. Even though

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<v Speaker 1>they're not moons, death stars and other space stations are

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<v Speaker 1>implicitly disqualified. Three, it has attained hydrostatic equilibrium. This means

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<v Speaker 1>the object has enough mass that over time, the force

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<v Speaker 1>of gravity has shaped it roughly into a sphere. This

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<v Speaker 1>would disqualify all those comets and asteroids that are shaped

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<v Speaker 1>like lumpy potatoes. Series is pleasantly, almost delightfully round. And

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<v Speaker 1>number four, it has not, as astronomers say, cleared the

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<v Speaker 1>neighborhood around its orbit. Over time, large bodies like planets

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<v Speaker 1>tend to eliminate other materials from their orbital zone. This

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<v Speaker 1>is why objects like Series and Pluto art planets. They

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<v Speaker 1>haven't cleaned for room. For Series. That room is the

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<v Speaker 1>asteroid belt, frankly, just about the dirtiest room in the

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<v Speaker 1>Solar System apart from the icy pig sty that is

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<v Speaker 1>the Kuiper Belt. So Series remains a dwarf planet, but

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<v Speaker 1>there is no means anything wrong with being a dwarf

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<v Speaker 1>planet because Series is fascinating. Here are a couple of

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<v Speaker 1>quick facts. Series is about nine hundred and fifty kilometers

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<v Speaker 1>or five d ninety miles in diameter, meaning if you

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<v Speaker 1>look at the disk head on, it is about the

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<v Speaker 1>size of Texas. But it's total surface area is about

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<v Speaker 1>two point eight million square kilometers or about one point

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<v Speaker 1>one million square miles. That's about as much real estate

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<v Speaker 1>as the country of Argentina. By itself. Series accounts for

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<v Speaker 1>a quarter of the mass of the entire asteroid belt.

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<v Speaker 1>If you were to take a cross section of Series,

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<v Speaker 1>you would find a rocky core at the center and

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<v Speaker 1>a dusty outer crust on the surface, but in between

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<v Speaker 1>them a subterranean mantle of water ice. This layer of

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<v Speaker 1>water ice has drawn a lot of attention, since anywhere

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<v Speaker 1>there is water, there's always the slim possibility that we

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<v Speaker 1>could discover life. Scientists sometimes speak of Series as a

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<v Speaker 1>proto planet or an embryonic planet. About four and a

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<v Speaker 1>half billion years ago, when the planets in our Solar

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<v Speaker 1>system were first forming, Jupiter's gravity prevented Series from becoming

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<v Speaker 1>a full fledged planet. This left it frozen in its

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<v Speaker 1>fetal state, so there may be a lot we can

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<v Speaker 1>learn from Series about how planets are born in young

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<v Speaker 1>solar systems. Check out the brainstuff channel on YouTube, and

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<v Speaker 1>for more on this and thousands of other topics, visit

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<v Speaker 1>how stuff works dot com.