Another moon for Uranus

Astronomers have confirmed the existence of the 21st moon known to be orbiting Uranus. Dubbed S/2001 U1, the satellite is one of six small Uranian moons that have elliptical orbits and don’t move in the same plane as the planet’s larger moons. Ranging from 10 to 20 kilometers in diameter, these so-called irregular moons seem to have been created by collisions between larger bodies during the formation of the planets.

Because S/2001 U1 is faint and lies at a great distance from Uranus, astronomers had to use several telescopes to confirm its status as a moon.

The first sighting was in August 2001 by a team led by Matthew J. Holman of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and J.J. Kavelaars of the Dominion Astrophysical Observatory in Victoria, British Columbia, with a telescope at the Cero Tololo Inter-American Observatory in La Serena, Chile. Christophe Dumas of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., and Philip Nicholson of Cornell University did follow-up observations at Palomar Observatory near Escondido, Calif. Astronomers also tracked S/2001 U1 using one of the European Southern Observatory’s 8-meter telescopes in Paranal, Chile.

Dumas and his colleagues reported their findings in a Sept. 30 circular of the International Astronomical Union.


If you have a comment on this article that you would like considered for publication in Science News, please send it to

More Stories from Science News on Planetary Science