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What Is The Dwarf Planet Ceres?

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Channel: BrainStuff - HowStuffWorks
Categories: Astronomy   |   Physics   |   Science  
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Don’t know what the dwarf planet Ceres is, and at this point you’re too afraid to ask? BrainStuff will give you the deets on this otherworldly object.

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Hi, I’m Jonathan, and this is Brainstuff. 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 Ceres. This meet-up is exciting news for space fanatics like me, but if you don’t know what Ceres is and at this point you’re too afraid to ask, we are here to lay down the facts you need to know.

Ceres first came to human attention when the Italian astronomer Giuseppe Piazzi spied a moving point of light from the Palermo Observatory on New Years’ Day in 1801. Piazzi named this new space-dot after the Roman deity Ceres, the goddess of grain and nutritious food crops.

Today, astronomers classify Ceres as a dwarf planet.

So, you might be wondering: What makes a dwarf planet different from a regular planet, or a comet or an asteroid?

According to the International Astronomical Union, a dwarf planet is any object that meets the following four criteria:

1.) It goes around the sun. That’s a check for Ceres.

2.) It’s not a moon. Another check for Ceres. (Even though they are no moons, Death Stars and other space stations are implicitly disqualified.)

3.) 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.

4.) 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 Ceres and Pluto aren’t planets: They haven’t cleaned their room. For Ceres, that room is the asteroid belt – frankly, just about the dirtiest room in the solar system, apart from the icy pigsty that is the Kuiper Belt.

So Ceres remains a dwarf planet, but there is by no means anything wrong with being a dwarf planet, because Ceres is fascinating. Here are some quick facts:

Ceres is about 950 kilometers (590 miles) in diameter, meaning if you look at the disc head-on, it’s about the size of Texas. But its total surface area is about 2.8 million square kilometers (1.1 million square miles). That’s about as much total real estate as the country of Argentina.

If you were to take a cross-section of Ceres, 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 Ceres as a protoplanet 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 Ceres from becoming a full-fledged planet. This left it frozen in its fetal state -- so there may be a lot we can learn from Ceres about how planets are born in young solar systems.


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