NASA scientists say they've managed to track a mysterious group of "outcast" near-Earth asteroids to their probable distant birthplace.
Using the space agency's Neowise space telescope, they've identified a family of asteroids traveling in orbits that are highly tilted, or inclined, from the solar system's planetary plane as a likely source of some near-Earth objects, or NEOs.
Of the estimated 700,000 asteroids orbiting in the main asteroid belt between Mars and Jupiter, one group known as the Euphrosyne family, at the farthest edge of that belt, has a highly unusual orbit shifted significantly above the planetary plane, also known as the ecliptic.
The group is named for its largest asteroid, Euphrosyne, believed to be a leftover remnant of a giant collision around 700 million years ago that created the orbiting group of smaller asteroids that carry its name.
That event, resulting in the 156-mile-wide asteroid — one of the 10 largest in the entire asteroid belt — and its smaller companions, may have been one of the last significant collisions in our solar system, astronomers say.
NEOs, with orbits around the solar system that sometimes bring them close to the path of the Earth, are studied for possible collision threats.
They can come from the asteroid belt or the more distant regions of the solar system, and scientists have attempted to discover the reservoirs of bodies within our solar system that feed the population of NEOs.
Researchers at NASA's Jet Propulsion Laboratory in Pasadena, California, say they think the Euphrosynes group could be the source for some NEOs determined to have distant, highly inclined orbits.
They say gravitational interaction with Saturn could move some of the asteroids into new orbits that eventually see them heading toward the sun — and the Earth.
"The Euphrosynes have a gentle resonance with the orbit of Saturn that slowly moves these objects, eventually turning some of them into NEOs," says Joseph Masiero, lead JPL researcher on the study. "This particular gravitational resonance tends to push some of the larger fragments of the Euphrosyne family into near-Earth space."
Masiero and his colleagues used Neowise to study 1,400 Euphrosyne objects with highly inclined elliptical orbits, characteristics the researchers say make them, and the entire Euphrosyne family, likely candidates as the source for some of the NEOs that have been detected.
"Neowise is a great tool for searching for near-Earth asteroids, particularly high-inclination, dark objects," Masiero says.
