This near-infrared image shows Uranus, its rings, and its five largest moons. The rings are much more apparent than they would be in a visible light image. This image was created using a telescope at the European Southern Observatory in Chile. Click on image for full size (31K JPEG) Image courtesy European Southern Observatory.

Astronomers have discovered new moons orbiting Uranus and Neptune. 2003 has been a banner year for moon discoveries; several new moons orbiting Jupiter, Saturn, and Neptune were announced earlier this year. All of the newfound moons are small, having diameters less than 100 km (60 miles).

Mark Showalter of Stanford University and NASA's Ames Research Center and Jack Lissauer of Ames discovered two new moons of Uranus that have been given the temporary names S/2003 U1 and S/2003 U2. At the time of their discovery in September, the two were the smallest moons yet found orbiting Uranus, having diameters of 16 km (12 miles) and 12 km (8 miles) respectively. The moons, which were discovered via observations made with the Hubble Space Telescope, both orbit closer to the planet than Uranus's five large moons (Ariel, Miranda, Oberon, Titania and Umbriel). S/2003 U2 orbits in a region crowded with eleven other small moons, all of which were discovered via observations made by Voyager.

Scott Sheppard and David Jewitt at the University of Hawaii discovered two other moons of Uranus, which are currently called S/2003 U3 and S/2001 U2. Both were found using the Subaru telescope on the top of the Mauna Kea volcano in Hawaii. S/2003 U3 is 11 km in diameter (7 miles) and takes about 4 years to complete an orbit around Uranus; S/2001 U2 is 12 km (8 miles) across and orbits so far from the planet that it takes almost 8 years to go around once! S/2001 U2 had originally been spotted in 2001 by Matthew Holman and J.J. Kavelaars, but they weren't able to make enough observations at that time to prove it was a satellite of Uranus, and astronomers hadn't been able to locate it since. Astronomers need to observe a new moon several times before they declare a discovery since the multiple observations allow them to determine the orbital path of the newly found satellite.

Two new moons of Neptune have also recently been found. S/2002 N4 was first seen by Holman and B. Gladman in August 2002. The discovery was confirmed with new observations in August and September of this year by Holman. The moon is roughly 60 km (37 miles) in diameter. S/2003 N1 was discovered by Jewitt, Sheppard and Jan Kleyna, again using the Subaru telescope. It is about 38 km (24 miles) across. Both moons orbit farther from their parent planet than any other moon so far discovered in the entire Solar System. Each moon orbits Neptune at an average distance of roughly 47 million km (29 million miles), and takes about 25 years to make it around the planet once! That distance is about one third as large as the distance from Earth to the Sun!

These new discoveries boost the total count of moons found around Uranus to 27 and around Neptune to 13. Stay tuned - it has been a good moon hunting season this year, and you never know when more new moons might be found!

This picture shows Uranus, its rings, and its five largest moons. The picture was taken in infrared "light", which makes the rings look brighter than normal. Click on image for full size (31K JPEG) Image courtesy European Southern Observatory.

Astronomers have discovered new moons orbiting the planets Uranus and Neptune. Counting the new moons, Uranus now has 27 moons that we know about. Neptune has 13 that have been found so far. All of the newfound moons are small, having diameters less than 100 km (60 miles).

Mark Showalter of Stanford University and NASA's Ames Research Center and Jack Lissauer of Ames discovered two new moons of Uranus. Those moons have been given temporary names: S/2003 U1 and S/2003 U2. The moons were found in pictures taken by the Hubble Space Telescope. Uranus has five large moons named Ariel, Miranda, Oberon, Titania and Umbriel. S/2003 U1 and S/2003 U2 are closer to Uranus than all of the large moons.

Scott Sheppard and David Jewitt discovered two more moons of Uranus. Those moons are called S/2003 U3 and S/2001 U2 for now. Sheppard and Jewitt used a telescope on top of a volcano in Hawaii to find these moons. S/2001 U2 has a big orbit and takes almost 8 years to go around Uranus!

Astronomers also found two new moons orbiting Neptune. Matthew Holman and B. Gladman discovered S/2002 N4. Jewitt, Sheppard and Jan Kleyna discovered S/2003 N1. These moons orbit very far from Neptune. They are farther away from their "home" planet than any other moon that has been found so far. They take about 25 years to go around Neptune once!

Some of the moons had been seen before in the last few years. To figure out the orbit of a moon, astronomers need to see it a few times to know how it moves. They don't count a moon as "discovered" until they are sure that it orbits a planet.

The planet Uranus and its rings are in the middle of this picture. You can also see the five biggest moons of Uranus. The new moons are too small to see in this picture. Click on image for full size (31K JPEG) Image courtesy European Southern Observatory.

Astronomers have found new moons around the planets Uranus and Neptune. Uranus now has 27 moons that we know about. Neptune has 13 that have been found so far.

Some of the new moons were found in pictures taken by the Hubble Space Telescope. Others were found using telescopes on Earth in Hawaii, Chile, and other places. Astronomers from around the world worked together to find the new moons.

The scientists found four new moons around Uranus. Uranus has five big moons named Ariel, Miranda, Oberon, Titania and Umbriel. All of the new moons are very small.

The astronomers also found two new moons around Neptune. Those moons have very large orbits. They are farther from Neptune than any other known moon is from the planet it goes around. The new moons of Neptune take about 25 years to go around once!