Uranus' New Moons

Uranus XVI and XVII

   Two new moons of Uranus, provisionally known as Uranus XVI (S/1997 U 1) and Uranus XVII (S/1997 U 2), have been discovered. The names Caliban and Sycorax have been proposed by the discoverers and will very likely be accepted by the IAU.

   Like the other irregular moons (eg. Jupiter's outer 8 moons, Phoebe and Nereid), these are probably captured asteroids. It is highly unlikely that they could have been formed initially in these orbits.

   The composition of the two moons, according Nicholson, "is probably a plum-pudding mixture of rocks and ice." Both moons are unusually red in color which may suggest a historical link with the Kuiper Belt.

   These are the dimmest moons ever to have been imaged with a ground-based telescope.

1986 U 10

Uranus XVIII

   This tiny moon is as yet unnamed.

   Imaged by Voyager 2 in 1986; discovered in 1999 by Erich Karkoschka of the Lunar and Planetary Lab of The University of Arizona in Tucson.

   It's orbit is nearly identical to that of Belinda, about 75,000 km from Uranus.

   It is about 40 km in diameter.

Open Issues

• We know next to nothing about these moons; will we be able to learn anything about them until another spacecraft is sent to Uranus?