Initial ground-based observations suggested Xena's diameter was about 30 percent greater than Pluto. The Hubble observations taken last December show Xena's diameter as 1,490 miles -- with an uncertainty of 60 miles. Pluto's diameter, as measured by Hubble, is 1,422 miles.
"Hubble is the only telescope capable of getting a clean visible-light measurement of the actual diameter of Xena," said Mike Brown, planetary scientist at the California Institute of Technology in Pasadena. Brown's research team discovered Xena and the team's research has been accepted for publication in the Astrophysical Journal.
Xena is located 10 billion miles from Earth with a diameter a little more than half the width of the United States.
Astronomers say because Xena is smaller than previously thought, but comparatively bright, it must be one of the most reflective objects in the solar system.
The Hubble Space Telescope is an international cooperative project between NASA and the European Space Agency.