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.

You might also be interested in:

Cool It! Game

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

Dwarf Planets

In 2006 the International Astronomical Union (IAU) approved a new classification scheme for planets and smaller objects in our Solar System. Their scheme includes three classes of objects: "small solar...more

Pluto

Pluto is a frigid ball of ice and rock that orbits far from the Sun on the frozen fringes of our Solar System. Considered a planet, though a rather odd one, from its discovery in 1930 until 2006, it was...more

Trans-Neptunian Objects (TNO)

There are lots of small worlds at the edge of our Solar System. They are made of ice and rock. They are further away from the Sun than most planets. They are further away than the 8th planet, Neptune....more

What is a planet?

Do you know what a planet is? Guess what... astronomers are not quite sure what a planet is! Mercury, Venus, Earth, and Mars are the planets closest to the Sun. They are definitely all planets. They are...more

Elliptical Orbits

Do you think Earth moves around the Sun in a circle? That is almost true, but not quite. The shape of Earth's orbit isn't quite a perfect circle. It is more like a "stretched out" circle or an...more

Pluto demoted - no longer a Planet!

Pluto has been officially demoted from its status as a planet. The International Astronomical Union (IAU), at a meeting in August 2006, voted on their first "official" definition of a planet....more

Makemake: a Dwarf Planet

Makemake is a dwarf planet in our Solar System. Makemake was discovered in March 2005 by a team of astronomers led by Mike Brown. Makemake officially became a dwarf planet in July 2008. There were three...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA