(CrashCourse Kids intro)

Jessi: We've had a great time exploring the solar system with you so far, and we're not done yet. If you've been joining us for the past few weeks, then you've gotten to meet all eight of the planets: the four rocky planets and the four gas giants.  And we've also explored some of the smaller objects that are flying around the solar system, like asteroids and comets.

But there's so much more to explore, including some things that, when it comes to their size, are kind of in between. They're smaller then planets, but they're bigger then asteroids. Scientists call them the dwarf planets.  

Dwarf planets are actually a lot like regular planets. They all have basically a round shape and they travel in a path around the sun. But unlike regular planets dwarf planets are much smaller and their trip around the sun is probably a lot bumpier. That's because while planets like Earth or Jupiter have a clear path around the sun, dwarf planets paths are full of lots of other stuff, like asteroids.

Think of orbits around the sun as being like lanes on a highway. Regular planets have a lane pretty much all to themselves, but dwarf planets are always sharing their lanes with lots of other things that are moving around with them.  So that's what makes a dwarf planet different from a regular planet: it's size, and the amount of stuff that's around it.

Even though dwarf planets are smaller than regular planets, they're just as exciting to learn about. Let's check out some of these dwarf planets up close. Squeaks, grab the telescope! So far astronomers have named five dwarf planets, more of which are very far from Earth. All but one of them are in an icy area way past Neptune called the Kuiper Belt.

First up is Pluto. Pluto, located just beyond Neptune, is probably the most famous of the dwarf planets. That's because it was the first object way out there that was discovered, and for a long time it was actually considered to be a regular planet. But then scientists discovered a lot of other planet-like things farther out in the solar system than Pluto, and they were orbiting the sun too. Some of these objects were even a little bigger than Pluto, and they all had a bunch of other space rocks cluttering up their orbits. So, scientists realized that Pluto was just one of many objects out there, and they decided that Pluto really wasn't a planet like Venus or Mercury, but instead it was a dwarf planet.

But, Pluto is still super interesting. Because it's so far from the sun, it's one of the coldest places in the solar system. Temperatures can dip below as 225 degrees below zero. So you'll definitely need your mittens if you go to Pluto.

Next up is Haumea. Because Haumea spins really really fast, a single day on this dwarf planet is also really really fast, just four hours. Astronomers think Haumea collided with another large object a long time ago. A crash like that might explain why it spins so fast and also why it has a more oval shape than other dwarf planets.

Moving on to Makemake. Because this planet was discovered around Easter time, astronomers once nicknamed it "Easter Bunny." Like the other dwarf planets we've seen, Makemake is also super cold. It's very bright, too, because there's lots of shiny ice on it, and thanks to some of the chemicals on its surface, it actually looks kind of pink. Look how pretty it is.

Next up is Eris. Eris is the biggest dwarf planet in the solar system. It's just a little bit bigger than Pluto and it even has its own tiny moon.

And our last dwarf planet is a little closer to home: Ceres. Ceres is the closest dwarf planet to the sun, located in the asteroid belt, that big band of space rocks floating around Mars and Jupiter. In addition to being closer to s than the rest of the dwarf planets, Ceres is also the smallest of them. It's so small that scientists consider it to be both a dwarf planet and a really big asteroid. The coolest thing about Ceres is that it's also the first dwarf planet to be visited by a spacecraft.

The spacecraft, called Dawn, didn't have any astronauts on it. It was more like a robot that took a lot of measurements and amazing pictures, which has given us the closest look we've gotten at a dwarf planet yet. Scientists hope that by studying Ceres, they'll be able to learn more about all of the dwarf planets. And even though they've only named five dwarf planets so far, experts think that they'll soon find hundreds more of them in our solar system. So Squeaks and I might have many more world to explore with you in the years to come, and I can't wait.

And if you have a question, or just something you'd like to learn more about, let us know by leaving a comment or emailing us at kids@thescishow.com. See you next time, guys.

(outro)