Astronomers- The oldest asteroid family discovered
(IANS) Astronomers have discover 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.
Kevin Walsh said, “The family we identified has no name, because it is not clear which asteroid is the parent.”
“This family is so old that it appears to have formed over four billion years ago, before the gas giants in the outer solar system moved into their current orbits. The giant planet migration shook up the asteroid belt, removing many bodies, possibly including the parent of this family,”.
Finding and studying asteroid families allows scientists to have better understanding of the history of main belt asteroids.
But it is challenging identifying the very oldest asteroid families of billions years old, 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.
The team leader Marco Delbo, an astronomer from the Observatory of Cote d’Azur in Nice, France added “Each family member drifts away from the centre of the family in a way that depends on its size, with small guys drifting faster and further than the larger guys,”
“If you look for correlations of size and distance, you can see the shapes of old families.”
“We identified all known families and their members and discovered a gigantic void in the main belt, populated by only a handful of asteroids. These relics must be part of the original asteroid belt. That is the real prize, to know what the main belt looked like just after it formed,” Walsh noted.
The team plans to apply this new technique to the entire asteroid belt to reveal more about
the history of the solar system by identifying the primordial asteroids versus fragments of collisions.