Images: Astronomers see three new planets

Ceres, named after the Roman goddess of agriculture, was discovered in 1801 by Giuseppe Piazzi. It was first called a planet, then demoted to asteroid status, and may be headed back to being a planet. Ceres, the largest object in the asteroid belt between Mars and Jupiter is about 600 miles in diameter--almost one fourth the size of the moon. It completes one orbit around the sun in about 4.6 years.

Earlier this year NASA cancelled, then reinstated, the Dawn mission which is now scheduled to launch in 2007. A probe will be sent on a four year journey to the minor planet Vesta where it will spend about a year before being sent to its next target, Ceres, where it will arrive in 2016.

NASA, ESA, J.Y. Li (University of Maryland) and G. Bacon (STScI)

This cutout view of Ceres shows that the potential planet may contain water. With no atmosphere, the possibility of life on Ceres is remote.

Credit: NASA, ESA, and A. Feild (STScI)

In 1978, Charon was discovered by James Christy who noted a bulge in images from the planet Pluto that moved, in this case, from the top to the bottom over time. Charon was named after a "ferryman of the dead" figure in Greek mythology.

Some astronomers are especially critical of giving new status to Charon, shown here to the right of Pluto. Charon's new status would come because it is big enough for gravity to crush all other forces and make it round. But so are some of Jupiter's and Saturn's moons, as well as Earth's.

On January 19, 2006 NASA launched the New Horizons spacecraft on a 3-billion mile journey to reach Pluto and Charon in the summer of 2015. The piano-sized craft, designed and built at Johns Hopkins University Applied Physics Laboratory, will travel at a record 36,000 miles per hour after bouncing off Jupiter's gravity field in February 2007. After passing the two(?) planets, the craft will be directed toward one more object in the Kuiper belt.

Who knows what the probe may find. It has only been traveling for seven months and two new moons and a planet have appeared on its route.

Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

The third new planet is officially named 2003 UB313 but is better known as Xena. It was discovered in 2005 from images taken in 2003 and is slightly larger than Pluto.

The name Xena comes from the TV series "Xena, Warrior Princess" and its moon is called Gabrielle, Xena's sidekick.