Astronomers identify oldest asteroid family

New York : Astronomers have identified the oldest known asteroid family, which extends throughout the inner region of the main asteroid belt.

The team also discovered a relatively sparse region of the main asteroid belt, where the few asteroids present are likely pristine relics from early in solar system history.

"The family we identified has no name, because it is not clear which asteroid is the parent," said Kevin Walsh, astronomer at Southwest Research Institute in the US and co-author of a study published online in the journal Science.

Finding and studying asteroid families allows scientists to better understand the history of main belt asteroids. But identifying the very oldest asteroid families, those billions of years old, is challenging, because over time, a family spreads out.

As asteroids rotate in orbit around the Sun, their surfaces heat up during the day and cool down at night. This creates radiation that can act as a sort of mini-thruster, causing asteroids to drift widely over time.

After billions of years, family members would be almost impossible to identify, until now. The team used a novel technique, searching asteroid data from the inner region of the belt for old, dispersed families.They looked for the "edges" of families, those fragments that have drifted the furthest.