Pictures captured by the Hubble Space Telescope show the second known interstellar object, 2I/Borisov, in all its cometary glory.
The images were taken by the telescope’s Wide Field Camera 3 on Oct. 12, when 2I/Borisov was 260 million miles from Earth. The object was discovered by Crimean amateur astronomer Gennady Borisov in August, and since then its path has been traced to far beyond our solar system.
2I/Borisov is currently zooming through our celestial neighborhood at a speed of 110,000 mph. The comet won’t come any closer than 190 million miles to us, with the closest approach expected on Dec. 7 — and it’s on a course to leave our solar system for good.
The next few weeks afford a golden opportunity to study one of the most alien objects ever known to come this close. And based on the analysis conducted to date, 2I/Borisov looks surprisingly familiar. The shape of the nucleus can’t be made out in the Hubble images, but it has the characteristic fuzzy look and chemical composition associated with comets in our own solar system.
“Though another star system could be quite different from our own, the fact that the comet’s properties appear to be very similar to those of the solar system’s building blocks is very remarkable,” Amaya Moro-Martin of the Space Telescope Science Institute said today in a news release.
The only other known interstellar object to be observed is ‘Oumuamua, a cigar-shaped asteroid that was spotted in 2017 as it swung through the solar system.
“Whereas ‘Oumuamua appeared to be a rock, Borisov is really active, more like a normal comet. It’s a puzzle why these two are so different,” said UCLA astronomer David Jewitt, who led the team behind the Hubble observations of the comet.
Hubble observations of 2I/Borisov are planned through next January, with more being proposed. Astronomers from the University of Washington are also on the case, analyzing observations made at the Apache Point Observatory in New Mexico.
Max Mutchler, a member of the Hubble observing team who’s based at the Space Telescope Science Institute, said there could be more surprises ahead.
“New comets are always unpredictable,” Mutchler said. “They sometimes brighten suddenly or even begin to fragment as they are exposed to the intense heat of the sun for the first time. Hubble is poised to monitor whatever happens next with its superior sensitivity and resolution.”