Karin Cluster

The Karin Cluster is a group of at least 90 asteroids in the Koronis family in the main belt. What makes them special is that scientists have used the orbits of 13 members to calculate backwards until they were all found to share the same orbit — that of the parent body from which they all originated.

The cluster is named for its largest member, 832 Karin which has a diameter of about 19 km (11.7 miles). It represents about 15–20% of the mass of the original body which had an estimated diameter of 33 km (20.5 miles). (832) Karin is an S-type asteroid. (4507) 1990FV was originally thought to be a member of the cluster but was identified in 2004 as an interloper. The other cluster members have diameters in the 1-7 km range (0.6-4.3 miles).

The cluster is believed to have been created 5.7 million years ago, making it the most recent known asteroid collision. Because the surfaces of the cluster members are relatively pristine, spectroscopic analyses can tell scientists much about their composition and could shed new light on the question of how closely asteroids and meteorites are related. The fact that we know when their surfaces were formed will also be useful in determining the rate of crater formation in asteroids. It is estimated that in about 100 million years the cluster will have dispersed to a degree where it cannot be separated from the background population of asteroids.

The cluster may also be the source of one of the interplanetary dust bands discovered by the IRAS satellite and may also have generated meteorites which would have compositions consistent with S-type asteroids and cosmic ray exposure ages of approximately 5.7 million years.

A study of the Karin cluster has for the first time detected the Yarkovsky effect in main belt asteroids.

References

1. Nesvorný, D., et al. 2002. The recent breakup of an asteroid in the main-belt region. Nature 417(6890):720-722.

2. Nesvorný, D., Bottke, W.F., Levison, H.F., Dones, L., 2003. Recent originof the Solar System dust bands. Astrophys. J. 591, 486–497.

3. Nesvorný, D., & Bottke, W. F. 2004. Detection of the Yarkovsky effect for main-belt asteroids. Icarus 170: 324-342.

4. Nesvorný, D et al. 2006. Karin cluster formation by asteroid impact. Icarus 183: 296-311.