An amateur astronomer has discovered a comet from another star system, divebombing its way into ours.
C/2019 Q4 (Borisov), named after Ukrainian skywatcher Gennady Borisov who first spotted it with his self-made telescope two weeks ago, is only the second such visitor from interstellar space ever recorded.
"Based on the available observations, the orbit solution for this object has converged to the hyperbolic elements shown below, which would indicate an interstellar origin," the International Astronomical Union's Minor Planet Center announced on Thursday (NZ time).
Tiny cigar-shaped 'Oumuamua dropped in at the end of 2017, but wasn't spotted until it was on its way out, leaving scientists little time to figure out what it was and where it came from.
C/2019 on the other hand, is much larger - a few kilometres across at least, possibly 10 - and still on its way here.
"This is the first highly active object that we've seen coming in from something that formed around another star," Queen's University Belfast astronomer Michele Bannister told National Geographic.
It's presently hard to see because of the blinding light of the sun, but from mid-October will reportedly be visible to astronomers for up to a year.
"Further observations are clearly very desirable, as all currently-available observations have been obtained at small solar elongations and low elevations," the Minor Planet Centre said. "Absent an unexpected fading or disintegration, this object should be observable for at least a year."
The best time will be in early December, when it's at its brightest, Sky and Telescope reported.
C/2019's closest approach to Earth will be 300 million kilometres - about twice the distance from here to the sun. 'Oumuamua came much closer - about 33 million kilometres - but wasn't spotted until more than a week later.
Initial suspicions were that C/2019 originated in the Oort Cloud, a large plane of space surrounding the solar system where comets dwell. This was ruled out when astronomers calculated its orbit was on a 44-degree angle to the rest of the planets - so it couldn't have been dragged in by a planet.
That, combined with its speed and trajectory, prove it's from somewhere far, far away.
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When 'Oumuamua was spotted, speculation ran wild on what it could be, thanks to its odd shape and the fact it sped up after slinging around the sun. There were claims it could be an alien probe or perhaps some kind of ancient alien space yacht.
Astronomers eventually settled on it being a comet.
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