Astronomers recently scrambled to observe an intriguing asteroid that zipped through the solar system on a steep trajectory from interstellar space—the first confirmed object from another star.
Now, new data from Nasa reveal the interstellar interloper to be a rocky, cigar-shaped object with a somewhat reddish hue.
The asteroid, named ‘Oumuamua by its discoverers, is up to 400 metres long and highly-elongated - perhaps 10 times as long as it is wide.
"That aspect ratio is greater than that of any asteroid or comet observed in our solar system to date. While its elongated shape is quite surprising, and unlike asteroids seen in our solar system, it may provide new clues into how other solar systems formed," Nasa said.
This unusual object had been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years
The observations and analyses were funded in part by NASA and appear in the November 20 issue of the journal Nature. They suggest this unusual object had been wandering through the Milky Way, unattached to any star system, for hundreds of millions of years before its chance encounter with our star system.
“For decades we’ve theorised that such interstellar objects are out there, and now – for the first time – we have direct evidence they exist,” said Thomas Zurbuchen, associate administrator for Nasa's Science Mission Directorate in Washington.
An interstellar asteroid similar to ‘Oumuamua passes through the inner solar system about once per year, but they are faint and hard to spot and have been missed until now
“This history-making discovery is opening a new window to study formation of solar systems beyond our own.”
The reddish object is completely inert, without the faintest hint of dust around it, suggesting that it is comprised of rock and possibly metals, has no water or ice, and that its surface was reddened due to the effects of irradiation from cosmic rays over hundreds of millions of years.
'Oumuamua is travelling about 38.3 kilometres per second relative to the Sun. Its location is approximately 200 million kilometres from Earth.
This remarkable object was discovered October 19 by the University of Hawaii’s Pan-STARRS1 telescope, funded by NASA’s Near-Earth Object Observations (NEOO) Program, which finds and tracks asteroids and comets in Earth’s neighborhood.
Astronomers estimate that an interstellar asteroid similar to ‘Oumuamua passes through the inner solar system about once per 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.
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