Second interstellar visitor confirmed, officially named
The International Astronomical Union (IAU) has now confirmed that a strange object discovered in our solar system on August 30 is unambiguously interstellar in origin. This makes it only the second such object, after ‘Oumuamua in 2017, and it’s now been given an official name.
On August 30, amateur astronomer Gennady Borisov discovered what looked like a comet, using a telescope he built himself. After follow-up observations were conducted by astronomers from around the world, it began to look like this object was on a hyperbolic trajectory – meaning it doesn’t circle the Sun but is just passing through our solar system.
Now a few weeks later, astronomers have been able to confirm that not only is the object undoubtedly interstellar, but it’s actually on the most hyperbolic path of any known comet. This confirmation comes from both the IAU and the NASA JPL Solar System Dynamics Group.
With its path now better known, astronomers have also been able to give it a proper name: 2I/Borisov. The 2I indicates that it’s the second interstellar object discovered, after ‘Oumuamua, while the latter part of the name honors its discoverer.
It is a very different object though. ‘Oumuamua is an asteroid, and a strangely-stretched-out one at that. Meanwhile, on closer inspection astronomers have been able to determine that 2I/Borisov is a comet – making it the first interstellar comet ever discovered. Its nucleus is a few kilometers wide, and observations of its spectrum indicate that besides its trajectory, it’s basically the same as any other comet.
Luckily, 2I/Borisov was discovered earlier in its visit than ‘Oumuamua, giving astronomers more time to study it. The window was only open for nine days for ‘Oumuamua, since it was discovered after it had swung past the Sun and was on its way out of the solar system. This time we have several months, with the object not expected to make its closest pass to the Sun until December 7.
After that, it will still be clear in the skies of the Southern Hemisphere through January 2020. Moderate-sized telescopes will be able to see it until about April, and larger professional telescopes can see it until about October 2020. Then it will exit the solar system and disappear into the inky depths of interstellar space once again, never to return.