May 30, 2013 | Press Trust India
Washington: Astronomers using data from NASA's Wide-field Infrared Survey Explorer (WISE) have identified 28 new families of asteroids in the main belt between Mars and Jupiter.
The findings are a critical step in understanding the origins of asteroid families, and the collisions thought to have created these rocky clans.
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. The cast-off pieces move together in packs, travelling on the same path around the Sun, but over time the pieces become more and more spread out.
"We're separating zebras from the gazelles," said Joseph Masiero of NASA's Jet Propulsion Laboratory in Pasadena, California, and lead author of the study.
"Before, asteroid family members were harder to tell apart because they were travelling in nearby packs. But now we have a better idea of which asteroid belongs to which family," Masiero said in a statement.
The new families were found in millions of infrared snapshots from the asteroid-hunting portion of the WISE all-sky survey, called NEOWISE.
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.
The main asteroid belt is a major source of near-Earth objects (NEOs), which are those asteroids and comets that come within 45 million kilometres 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.
"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 programme executive for the Near-Earth Object Observation Programme at NASA Headquarters in Washington.
"This will help us trace [near-Earth asteroids] back to their sources and understand how some of them have migrated to orbits hazardous to the Earth," Johnson said.
The next step for the team is to learn more about the original parent bodies that spawned the families.
The study was published in the Astrophysical Journal.