(USA Today) It came from outer space.
For the first time ever, astronomers have discovered an asteroid that’s entered our solar system from interstellar space.
The object is shaped like a cigar and is about a quarter-mile long.
“This thing is an oddball,” said Karen Meech of the University of Hawaii’s Institute for Astronomy, who led an international team that studied the interstellar interloper.
Although the object is similar in composition to some objects in our solar system, its long shape is unlike anything found around our sun.
“For decades we’ve theorized that such interstellar objects are out there, and now — for the first time — we have direct evidence they exist,” said NASA's Thomas Zurbuchen in a statement. “This history-making discovery is opening a new window to study formation of solar systems beyond our own.”
Named Oumuamua, (Hawaiian for "scout" or "messenger"), astronomers say the asteroid may well have been wandering through our Milky Way galaxy, unattached to any star system, for hundreds of millions of years before its chance encounter with our own solar system.
This "reflects the way this object is like a scout or messenger sent from the distant past to reach out to us," the authors wrote in the study, which was published Monday in the peer-reviewed British journal Nature.
The asteroid was first spotted in October by Meech's team using the Pan-STARRS1 telescope atop Mount Haleakala in Maui, Hawaii. In the weeks, since, other ground-based telescopes around the world and space-based telescopes in orbit have continued to monitor Oumuamua as it zips through the solar system at about 85,700 mph.
It will pass out of range of our telescopes in mid-December, bound for the constellation Pegasus.
The object "has a reddish color, similar to objects in the outer solar system," and is completely inert, without the faintest hint of dust around it, Meech said.
This suggests that Oumuamua is dense, made up of rock and possibly metals, has no water or ice and that its surface was reddened because of the effects of irradiation from cosmic rays over hundreds of millions of years.
The title of the study is "A brief visit from a red and extremely elongated interstellar asteroid."
Astronomers believe that interstellar asteroids such as Oumuamua pass through our solar system about once a year, but they are faint and hard to spot and have been missed until now. It is only recently that survey telescopes, such as Pan-STARRS, are powerful enough to have a chance to discover them.
“What a fascinating discovery this is,” said Paul Chodas of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It’s a strange visitor from a faraway star system, shaped like nothing we’ve ever seen in our own solar system neighborhood.”