Space rock may be a unique visitor
A mysterious object detected hurtling past the Sun could be the first space rock traced back to a different solar system, according to astronomers tracking it.
While other objects have previously been mooted as having interstellar origins, experts say the latest find, an object estimated to be less than 400 metres in diameter, is the best contender yet.
‘‘The exciting thing about this is that this may be essentially a visitor from another star system,’’ said Dr Edward Bloomer, astronomer at the Royal Observatory Greenwich.
If its origins are confirmed as lying beyond our solar system, it will be the first space rock known to have come from elsewhere in the galaxy.
Observations published by the Minor Planet Centre at the Harvard-Smithsonian Centre for Astrophysics reveal that the object is in a strong hyperbolic orbit – in other words, it is going fast enough to escape the gravitational pull of the Sun.
Objects originating from, and on long-period orbits within, our solar system can end up on a hyperbolic trajectory, and be ejected into interstellar space – for example, if they swing close by a giant planet, since the planet’s gravity can cause objects to accelerate. But Dr Gareth Williams, associate director of the Minor Planet Centre, said this wasn’t the case for the newly discovered body.
‘‘When we run the orbit for this [object] back in time, it stays hyperbolic all the way out – there are no close approaches to any of the giant planets that could have given this thing a kick,’’ he said. ‘‘If we follow the orbit out into the future, it stays hyperbolic. So it is coming from interstellar space and it is going to interstellar space.’’
According to observations made by astronomers, the object entered our solar system from above, passing just inside Mercury’s orbit and travelling below the Sun, before turning and heading back up through the plane of the solar system towards the stars beyond. At its closest, on September 9, the object was 37.6 million kilometres from the Sun.
The object was first spotted earlier this month by an observatory in Hawaii, and astronomers around the world are now following its path.