NASA and ESA astronomers have released new Hubble Space Telescope images of one of the two interstellar objects yet discovered, known as 2l/Borisov. The captures detail the way the objects look just before and immediately after its apogee that occurred on December 8th.
The images are momentous, as we have never seen an interstellar body sweeping so close to the Sun. 2I/Borisov was discovered on August 30th of this year by comet hunter Gennady Borisov in Crimea and is now labeled as a comet. The object was approximately twice as far as our planet is from the Sun at its closest approach, and is located in the winner margin of the asteroid belt found between Mars and Jupiter.
The Second-Known Interstellar Object so Far
Its recent passing near the Sun was, in fact, not a close encounter for a comet. However, because comets are most dynamic when they pass close to a star, scientists hoped to capture 2I/Borisov demonstrate an outburst or some other movement. Even so, there were no outbursts coming from 2I/Borisov, but the Hubble Space Telescope’s observations did provide some significant insights.
Astronomer David Jewitt of UCLA, who led the team of researchers that found the images, said: “Hubble gives us the best upper limit of the size of comet Borisov’s nucleus [core], which is the really important part of the comet. Surprisingly, our Hubble images show that its nucleus is more than 15 times smaller than earlier investigations suggested it might be. Our Hubble images show that the radius is smaller than half-a-kilometer [3 miles].”
Knowing the overall size of the nucleus is useful for beginning to predict how regular such cosmic bodies might be in the Solar System and our galaxy,” he added.
2I/Borisov is the second interstellar object that is captured passing through our system and the first known interstellar comet. The first interstellar body was found by researchers in Hawaii in 2017, and was named 1I/’Oumuamua, which, translated from Hawaiian means ‘Scout.’
More Interstellar Objects to be Discovered
‘Oumuamua was detected as coming from outside the Solar System, based on its orbit shape. However, it could not be labeled as a comet, in spite of the fact that comets are most probably nominees for becoming interstellar bodies. This comet was, though, a peculiarly long and slim object, and did not show any signs of expelling gas or a tail. It looked more like an asteroid than a regular comet.
Moreover, it had already had its apogee when astronomers first detected it, already heading out of our Solar System once again. Spotting the second-known interstellar object, 2I/Borisov, before and after its apogee, was an incredible achievement for researchers.
Now, both interstellar objects are traveling out of our Solar System, and by the middle of the year 2020, 2I/Borisov will have passed by Jupiter‘s distance of 500 million miles (800 million kilometers) on its journey to the interstellar space.
Now that they’ve discovered the first two interstellar bodies, astronomers are hoping to find many more in the years to come.