Uranus' New Moons

   Two new moons of Uranus, provisionally known as S/1997 U 1 and S/1997 U 2, have been discovered. S/1997 U 1 orbits about 6 million km from Uranus and is about 80 km in diameter. S/1997 U 2 orbits about 8 million km from Uranus and is about 160 km in diameter. These size estimates are based on their apparent brightness and assuming an albedo of about 7%. The orbits are retrograde and highly inclined (and only very approximate at this time).

   These moons have not yet been named.

   Discovered by Brett Gladman, Phil Nicholson, Joseph Burns, and JJ Kavelaars using the 200 inch Hale telescope; the first images were taken 1997 Sept 6 and 7.

   The image above is the discovery image of S/1997 U 1; the one to the right is S/1997 U 2.

   Prior to this discovery, Uranus was the only one of the gas giants not known to have "irregular" moons, that is, ones whose orbits are not direct and approximately in the plane of the planet's equator.

   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.

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

More about these moons

(Note: in some of the material below, S/1997 U 1 is refered to as the "fainter" of the two and S/1997 U 2 as the "brighter" one.)

Open Issues

Contents ... Uranus ... Oberon ... New Moons ... Neptune ... Data Host

Bill Arnett; last updated: 1998 Mar 17