NEW NAMES FOR URANIAN SATELLITES

The distant planet Uranus has been a fruitful target for planetary observers lately, with five satellites discovered telescopically within the last three years. (A sixth, discovered last year in Voyager images from 1986, awaits confirmation.) Three of the new moonlets were spotted in July 1999 by an international collaboration of astronomers working at the Canada-France Hawaii Telescope atop Mauna Kea.

In the last few months further observations were used to refine their orbits, and today astronomers meeting in Manchester, England, formally numbered the satellites and adopted provisional names for them. All three are characters from Shakespeare's The Tempest.

Prospero (formerly S/1999 U 3, now numbered XVIII) is 16.1 million kilometers from Uranus on average and takes 5.33 years to complete one orbit. In The Tempest, Prospero is a powerful magician who enslaves Ariel (the name of another Uranian satellite).

Setebos (formerly S/1999 U 1, now XIX) has the most eccentric orbit, which ranges in distance from 8.1 to 27.1 million km and has a period of 6.12 years. Setebos, the god of Sycorax, is mentioned several times in Shakespeare's play.

Stephano (formerly S/1999 U 2, now XX) takes 1.85 years to circle Uranus at an average distance of 7.9 million km. Serving as a butler on Ariel's ship, Stephano and Caliban plot to murder Prospero. Although the monikers received unanimous approval by the IAU's Working Group for Planetary System Nomenclature, they will remain provisional until approved by the Task Group for Outer-Planet Nomenclature and then its General Assembly. The discovery team includes Brett Gladman, Jean-Marc Petit, and Hans Scholl (all of the Observatoire de la Cote d'Azur in Nice, France), J. J. Kavelaars (McMaster University, Canada), and Matthew Holman (Harvard-Smithsonian Center for Astrophysics, U.S.).

Unlike the planet's inner moons, these new finds are considered "irregular," because they occupy distant, eccentric, highly inclined orbits and travel in directions generally opposite that of Uranus's rotation. (Caliban and Sycorax, the satellites found in 1997, are also in retrograde orbits.) Based solely on their brightness, they appear to be about 20 km across.

Although the monikers received unanimous approval by the IAU's Working Group for Planetary System Nomenclature, they will remain provisional until approved by the Task Group for Outer-Planet Nomenclature and then its General Assembly. The discovery team includes Brett Gladman, Jean-Marc Petit, and Hans Scholl (all of the Observatoire de la Cote d'Azur in Nice, France), J. J. Kavelaars (McMaster University, Canada), and Matthew Holman (Harvard-Smithsonian Center for Astrophysics, U.S.).

Unlike the planet's inner moons, these new finds are considered "irregular," because they occupy distant, eccentric, highly inclined orbits and travel in directions generally opposite that of Uranus's rotation. (Caliban and Sycorax, the satellites found in 1997, are also in retrograde orbits.) Based solely on their brightness, they appear to be about 20 km across.