Two More Moons Discovered by Hubble

Thanks to the Hubble's great eyes, we can now add two more moons to those known to be orbiting Uranus. The two most recently-discovered rocks, each just eight or ten miles in their major dimension (they're believed to be irregularly-shaped), can now join the ten 'official' moons discovered by Voyager in 1986, and the five we knew about before that.

Being able to see something that small, from a distance of about 1,700,000,000 miles away, attests to the Hubble's design and subsequent repairs.

The new satellites have cute names: S/2003 U 1 and S/2003 U 2; U1 is the bigger of the two. U1's orbit is between that of Puck and the big moon Miranda. It's a fast little fella, circling the big planet in just 22 hours and 9 minutes, at an altitude of 60,000 miles.

The smaller U2, with an orbit near Belinda's (46,400 miles up from the surface), also wastes no time -- its cycle is just under 15 hours.

The two tiny moons have dark surfaces -- with a reflectance equivalent to blacktop -- and were hard to detect. Their brightness is about one forty-millionth that of the parent planet's.

How many moons does Uranus have? There's five big ones, and 13 little ones... that we know about. The jury's still out on the 'final' number -- but Hubble is showing that even the tiniest rocks are becoming visible. [Saturn has 17 known moons; it's currently #2 in the count --ed.]

FMI: www.nasa.gov