NASA WISE mission finds lost asteroid family members

This artist's conception shows how families of asteroids are created. 

Over the history of our solar system, catastrophic collisions between asteroids located in the belt between Mars and Jupiter have formed families of objects on similar orbits around the sun. 

Image credit: NASA/JPL-Caltech

Data from NASA's Wide-field Infrared Survey Explorer (WISE) have led to a new and improved family tree for asteroids in the main belt between Mars and Jupiter.

Astronomers used millions of infrared snapshots from the asteroid-hunting portion of the WISE all-sky survey, called NEOWISE, to identify 28 new asteroid families.

The snapshots also helped place thousands of previously hidden and uncategorized asteroids into families for the first time.

The findings are a critical step in understanding the origins of asteroid families, and the collisions thought to have created these rocky clans.

"NEOWISE has given us the data for a much more detailed look at the evolution of asteroids throughout the solar system," said Lindley Johnson, the program executive for the Near-Earth Object Observation Program at NASA Headquarters in Washington.

"This will help us trace the NEOs back to their sources and understand how some of them have migrated to orbits hazardous to the Earth."

The main asteroid belt is a major source of near-Earth objects (NEOs), which are those asteroids and comets that come within 28 million miles (45 million kilometers) of Earth's path around the sun.

Some near-Earth objects start out in stable orbits in the main asteroid belt, until a collision or gravitational disturbance flings them inward like flippers in a game of pinball.

The NEOWISE team looked at about 120,000 main belt asteroids out of the approximately 600,000 known.

They found that about 38,000 of these objects, roughly one third of the observed population, could be assigned to 76 families, 28 of which are new.

In addition, some asteroids thought to belong to a particular family were reclassified.

An asteroid family is formed when a collision breaks apart a large parent body into fragments of various sizes.

Some collisions leave giant craters. For example, the asteroid Vesta's southern hemisphere was excavated by two large impacts.

Other smash-ups are catastrophic, shattering an object into numerous fragments, as was the case with the Eos asteroid family.

The cast-off pieces move together in packs, traveling on the same path around the sun, but over time the pieces become more and more spread out.

More information: Paper: dx.doi.org/10.1088/0004-637X/770/1/7