Hubble Finds That 2003 UB313 is Slightly Larger Than Pluto

FOR RELEASE: 1:00 pm (EDT) April 11, 2006

Erica Hupp/Dwayne Brown
Headquarters, Washington
(Phone: 202/358-1237/1726)

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
(Phone: 410/338-4514; E-mail: )

PRESS RELEASE NO.: STScI-PR06-16

HUBBLE FINDS THAT THE 'TENTH PLANET' IS SLIGHTLY LARGER THAN PLUTO

NASA's Hubble Space Telescope has resolved the "tenth planet,"
nicknamed
"Xena," for the first time and has found that it is only just a little
larger than Pluto. Though previous ground-based observations suggested
that Xena was about 30 percent greater in diameter than Pluto, Hubble
observations taken on Dec. 9 and 10, 2005, yield a diameter of 1,490
miles (with an uncertainty of 60 miles) for Xena. Pluto's diameter, as
measured by Hubble, is 1,422 miles.

Xena is officially catalogued as 2003 UB313. It is the large object at
the bottom of this artist's concept. A portion of its surface is lit by
the Sun, located in the upper left corner of the image. Xena's
companion, Gabrielle, is located just above and to the left of Xena.

For electronic images and additional information about the research on
the Web, visit:
http://hubblesite.org/news/2006/16
http://www.nasa.gov/hubble

For more information, contact Robert Tindol, California Institute of
Technology, Pasadena, CA, (phone) 626-395-3631, (e-mail)
, or Mike Brown, California Institute of Technology,
Pasadena, CA, (phone) 626-395-8423, (e-mail) .

The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency. The Space Telescope Science
Institute in Baltimore conducts Hubble science operations. The
Institute
is operated for NASA by the Association of Universities for Research in
Astronomy, Inc., Washington.