KNOXVILLE, Tenn., Oct. 7 (UPI) -- That planets have moons is old news to most people but a U.S. planetary scientist says up 20 percent of asteroids also have orbiting companions.
Joshua Emery at the University of Tennessee at Knoxville is part of an international team of planetary astronomers searching for moons around asteroids, a university release said Friday.
The team's research has focused on the asteroid Minerva, known to possess two moons.
"Minerva was thought to be a pretty typical, unremarkable asteroid until we discovered its two moons," Emery said. "Now, interest in this system has grown and, through a lot of new observations from both ground-based and space-based telescopes, we have developed a much more detailed understanding of Minerva and its moons."
Minerva is different from other large asteroids with moons, he said, because it has been found to be denser.
"All other large main-belt asteroids with one or more moons are very porous," Emery said. "Such high porosity strongly suggests that they are piles of rubble held together by gravity rather than solid rocks."
The astronomers used precise determinations of the moons' orbits, shape, size and mass to determine Minerva's density.
