Scott S. Sheppard and David Jewitt at the University of Hawaii have
discovered 2 new outer satellites of Uranus designated S/2001 U2 and S/2003
U3. The discovery images were obtained from the Subaru 8.3m telescope atop
Mauna Kea in Hawaii on August 29, 2003. Further observations by the Hawaii
team using the Gemini 8.2m telescope allowed Brian Marsden at the Minor
Planet Center to link the satellites to independent discovery observations
obtained in 2001 by a group lead by Matt Holman and JJ Kavelaars. The 2001
observations were not enough to determine if the objects were satellites of
Uranus and no reliable orbits were found. They were than lost until
discovery in 2003 by the Hawaii team.
The new Uranus satellite S/2001 U2 was announced by the International
Astronomical Union on October 1 ( IAU Circular 8213 ) and S/2003 U3 on
October 9 ( IAU Circular 8217 ). The new satellites are about 12 and 11
kilometers in diameter respectively. S/2001 U2 has an orbital period of
about 8 years and is in a retrograde orbit. S/2003 U3 has an orbital period
of just over 4 years and is the first prograde irregular satellite
discovered around Uranus. All the giant planets now have known prograde and
retrograde irregular satellites.
Uranus now has 27 known satellites of which 9 have irregular orbits.
