Scientists discover moon orbiting 10th planet
The astronomers who claim to have discovered the 10th planet in the solar system have made another intriguing announcement: it has a moon.
While observing the new, so-called planet from Hawaii last month, a team of astronomers led by Michael Brown of the California Institute of Technology spotted a faint object trailing next to it. Because it was moving, astronomers ruled it was a moon and not a background star, which is stationary.
The moon discovery is important because it can help scientists determine the new planet's mass.
The moon is about 155 miles wide and 60 times fainter than Xena, the farthest-known object in the solar system. It is currently 9 billion miles away from the sun, or about three times Pluto's current distance from the sun.