Welcome to brain Stuff from How Stuff Works. Hi, I'm Christian Seger, and this is brain Stuff. If you follow the latest in space gossip, you might have heard about a little rendezvous between a NASA probe called Dawn and an object in space known as the dwarf planet Series. This meet up is exciting news for space fanatics. But if you don't know what Series is, and at this point you're too afraid to ask, well, we are here
to lay down the facts you need to know. Series first came to human attention when the Italian astronomer Giuseppe Piazzi spied a moving point of light from the Palermo Observatory on New Year's Day in eighteen o one. Yeah, eighteen o one. That means Series was actually discovered almost a hundred and thirty years before the former planet and now fellow dwarf planet, Pluto. Piazzi correctly deduced that the object was somewhere between the orbits of Mars and Jupiter.
In reality, that zone contains the thing we now know as the asteroid Belt, a loose ring of rocky objects, of which Series is the largest. Piazzi named this new space dot after the Roman deity Series the goddess of grain and nutritious food crops. Historically, astronomers have gone back and forth about the status of this object. Piazzi himself initially thought it might be a comet. It has also been known as a planet and as an asteroid, but
today astronomers classify Series as a dwarf planet. So you might be wondering what makes a dwarf planet different from, you know, a regular planet or a comet or an asteroid. Well, according to the International Astronomical Union, a dwarf planet is any object that meets the following four criteria. First, it goes around the Sun. Okay, that's a check for Series. Two, it's not a moon. Another check for Series. Even though they're not moons, death stars and other space stations are
implicitly disqualified. Three, it has attained hydrostatic equilibrium. This means the object has enough mass that over time, the force of gravity has shaped it roughly into a sphere. This would disqualify all those comets and asteroids that are shaped like lumpy potatoes. Series is pleasantly, almost delightfully round. And number four, it has not, as astronomers say, cleared the neighborhood around its orbit. Over time, large bodies like planets
tend to eliminate other materials from their orbital zone. This is why objects like Series and Pluto art planets. They haven't cleaned for room. For Series. That room is the asteroid belt, frankly, just about the dirtiest room in the Solar System apart from the icy pig sty that is the Kuiper Belt. So Series remains a dwarf planet, but there is no means anything wrong with being a dwarf planet because Series is fascinating. Here are a couple of
quick facts. Series is about nine hundred and fifty kilometers or five d ninety miles in diameter, meaning if you look at the disk head on, it is about the size of Texas. But it's total surface area is about two point eight million square kilometers or about one point one million square miles. That's about as much real estate as the country of Argentina. By itself. Series accounts for a quarter of the mass of the entire asteroid belt.
If you were to take a cross section of Series, you would find a rocky core at the center and a dusty outer crust on the surface, but in between them a subterranean mantle of water ice. This layer of water ice has drawn a lot of attention, since anywhere there is water, there's always the slim possibility that we could discover life. Scientists sometimes speak of Series as a
proto planet or an embryonic planet. About four and a half billion years ago, when the planets in our Solar system were first forming, Jupiter's gravity prevented Series from becoming a full fledged planet. This left it frozen in its fetal state, so there may be a lot we can learn from Series about how planets are born in young solar systems. Check out the brainstuff channel on YouTube, and for more on this and thousands of other topics, visit how stuff works dot com.