Some Cosmic Dust Belts Not So Dusty
John P. Millis, Ph.D. for redOrbit.com – Your Universe Online
Besides the planets, comets, and asteroids that orbit our Sun, there are belts of rock and ice. Within these belts are dust particles, some which are fractions of a millimeter in size. As scientists have studied the heavens, they have located such disks orbiting other stars.
“At least one fifth of stars are surrounded by dust belts like these,” Alexander Krivov from the Friedrich-Schiller-University Jena explains. “They are the remains of the formation of planets, in which the unused, building materials are collected.”
But Krivov and a team of astronomers have found six stars that contain belts that are quite peculiar. While the stars themselves are similar to our Sun, the disks are much larger and colder at minus 250 degrees Celsius. As a result, the team concluded that the disks must be lacking in small dust particles, which result from collisions within the disk. As Krivov explains, “Small dust particles are much hotter than the temperatures observed by us.”
Yet, it is also unlikely that the disks contain particles much larger than a few kilometers in size. “If there were any bigger objects, the disks would be much more dynamic, the bodies would collide and thereby generate dust,” says Krivov.
The disks are most likely the remnants of the planet formation process, which for some reason must have been halted. “We don’t know why the development stopped,” Krivov says. “But the cold debris disks are proof that such belts can exist for over billions of years.”
Data for this study were acquired by the Herschel Space Observatory, which entered retirement in April. Now the scientists must wait for new observatories, such as the ALMA radio telescope in Chile to come on line to further study these systems.
Results are published in the Astrophysical Journal.