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This picture shows the dwarf planet Eris. It also shows its moon. The moon is the smaller dot to the right of Eris. The moon's name is Dysnomia.
Click on image for full size
Image courtesy W. M. Keck Observatory.

Eris - a dwarf planet

Eris is a dwarf planet in our Solar System. Eris is a lot like Pluto, which is also a dwarf planet. Eris and Pluto are both very far from the Sun. They are both very, very cold.

Eris was discovered in July 2005. It was found by Michael Brown, Chad Trujillo, and David Rabinowitz. When it was first discovered, the astronomers called it by the nickname "Xena".

Eris is hard to see, even using the biggest telescopes in the world, because it is so far away. Eris is probably a little bigger than Pluto. When scientists first found Eris, some called it the "tenth planet". Astronomers decided they needed a new name for small planets like Eris and Pluto. They decided to call them dwarf planets.

Eris has one moon. The name of the moon is Dysnomia.

It takes Xena 557 years to orbit the Sun once! Xena's orbit is strange. The orbit isn't round, and it is tilted a lot.

Last modified February 10, 2009 by Randy Russell.

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The Summer 2010 issue of The Earth Scientist, available in our online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.

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