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Solar system
Dwarf planet, Eris

4.5 billion years, about the same age as the Sun


Solar system, Kuiper Belt region

Avg. distance from the Sun

10.2 x 109 km (6.34 x 109 mi), but Eris' orbit is so elongated during its trip around the Sun that it can be as far as 14.6 x 109 km (9.07 x 109 mi) and as near as 5.65 x 109 km (3.51 x 109 mi).


Approximately 2,500 km (1,500 mi)


1.6 x 1022 kg

Orbital period around the Sun

557 Earth years (203,600 Earth days)

Number of moons

One, named Dysnomia

Distinguishing features

Eris, originally nicknamed Xena, is the largest known dwarf planet in the solar system. Its elongated orbit takes it far outside of the main region of the Kuiper Belt.

Eris and its moon, Dysnomia.

Enlarge Image


"Fast Facts: Dwarf planet, Eris" is a table that lists Eris' age, location, average distance from the Sun, diameter, mass, orbital period around the Sun, number of moons, and distinguishing features. The text describes the elongated orbit of this largest of known dwarf planets. A picture of Eris is included.

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Adaptable, at teacher's discretion
How to use in the classroom

Use this resource as:

A source of information. Read the table to find out about this object.

A reading activity. Give each student a planet-themed Fast Facts table. Ask students to locate specific object characteristics, such as the number of moons or the diameters of their respective planets.

A large-number recognition and ordering activity. Have students review several planet Fast Fact tables, including this one. Have students read the tables to find each planet's distance from the Sun. Then ask them to arrange the planets according to their distance from the Sun, from closest to farthest. Students also can arrange the planets according to their mass and/or diameter, from smallest to largest.

A unit conversion activity. Have students change the distances in either kilometers or miles into astronomical units. One astronomical unit (AU) is the average distance from Earth to the Sun, which equals 149,600,000 km, or 92,960,000 miles.

A compare/contrast activity. Have students review several Fast Facts tables for planets. Students match the planets to statements that describe a unique feature of each planet, such as: This planet is closest to the sun, or this is the largest known dwarf planet. Either the teacher or the students can generate the statements using information from the Fast Facts. Students also can create graphic organizers comparing the features of planets and dwarf planets.

An inquiry tool. Have students write down questions they would like answered about the image and the information in the Fast Facts table.

An engagement tool. Involve students in a discussion.


Related materials

HubbleSite press release: "Astronomers Measure Mass of Largest Dwarf Planet"

Amazing Space resources by topic: Solar system