Pan-STARRS 1 - a telescope in Hawaii created to find near-Earth objects - spotted the asteroid on October 19. This is the first time scientists have discovered an asteroid from outside the solar system, and the finding has been published in Nature. The longest known objects in the solar system now are no more than three times as long as they are wide. Spectroscopic measurements show that the object's surface is consistent with comets or organic-rich asteroid surfaces found in our own Solar System. But they're hard to detect and until recently telescopes weren't strong enough to detect them.
One of the things that makes this rock super special is that the rock is the FIRST to be discovered that formed in another solar system and travelled to our solar system. Once bigger telescopes start to come online, like the Large Synoptic Survey Telescope that's being built in Chile, astronomers will be able to see even more visiting rocks.
Along with its technical title of 1I/2017 U1, the cosmic rock has been given the Hawaiian name of 'Oumuamua, which the university statement says "reflects the way this object is like a scout or messenger sent from the distant past to reach out to us". This high "orbital eccentricity" as it is called, therefore suggests the most likely explanation is 'Oumuamua made the journey from outside our solar system.
The shape of the object, believed to be the first asteroid or comet to be observed by humans, is 10 times as long as it width and has never been seen before.
Astronomer Jayadev Rajagopal said in an email that it was exciting to point the Arizona telescope at such a tiny object "which, for all we know, has been traveling through the vast emptiness of space for millions of years". While that might be true in terms of the object's composition, calculations of its orbit revealed that it could not have come from our own solar system.
"'We also found that it has a dark red colour, similar to objects in the outer Solar System, and confirmed that it is completely inert, without the faintest hint of dust around it". Early estimates suggest that it is coming roughly from the direction of bright star Vega, in the northern constellation of Lyra, an ESO report said.
An artist's impression of the first confirmed interstellar asteroid.
The asteroid is now heading towards Jupiter and is predicted to leave our solar system in 2019, continuing its long journey towards the Pegasus constellation. These objects, usually identified by the highly angled paths they take through our solar system, could provide clues about the composition of far-off solar systems. "This serendipitous discovery is bonus science enabled by NASA's efforts to find, track and characterize near-Earth objects that could potentially pose a threat to our planet".
"We are continuing to observe this unique object", said ESO's Olivier Hainaut, and added "we hope to more accurately pin down where it came from and where it is going next on its tour of the galaxy". So we should probably expect many more of these interstellar visitors to get spotted now we are looking for them.