Nadia Higgins - Dwarf Planets: Pluto and the Lesser Planets

These space scientists changed the way people thought about our solar system. For years, tiny Pluto had been the ninth planet from the Sun. But now, scientists were finding other space objects that seemed a lot like Pluto. Our Solar SystemPluto Could they all be planets? No, a new category was needed. Pluto and other similar bodies were now dwarf planets. Sorry, PlutoFor many, losing Pluto was hard to take. But science is full of big changes.

Every day, we learn more about space. Scientists rethink old ideas to fit new facts.Pluto Three Rules for Dwarf Planets Scientists have named five dwarf planets. Each is smaller than a planet but bigger than other space objects. All five dwarf planets are smaller than Earths Moon. HaumeaMakemakeEarths MoonPlutoErisCeresEarth How do scientists know what counts as a dwarf planet? They follow three rules. First, a dwarf planet has to orbit, or travel around, the Sun.

Moons twirl around planets. So they are not part of this group. Second, a dwarf planet has to be round. In space, only objects of certain size form into balls. So a dwarf planets roundness shows that it is over a certain size. Each planet follows its own path around the Sun.How Round?Some scientists say the rules for dwarf planets arent clear.

For example, what counts as round? Dwarf planet Haumea is shaped like an egg.Haumea Third, a dwarf planet shares its path around the Sun with other objects. This shows its not as big as a planet. A true planet would not have other objects share its orbit. True planets are so big that all objects in their path are pulled in by their gravity. Both Pluto and Eris cross the orbit paths of other planets. That shows they are dwarf planets. Five Dwarf Planets, and Counting Dwarf planets share several traits with planets.