Comet Borisov is the first to arrive in the solar system from afar. It has a lot of mystery

The unusual composition of Borisov’s comet may reveal the mystery of its origin. The fact is that this is the first comet from the interstellar medium seen in the solar system.

Two groups of scientists independently of each other found significant differences in its isotopic composition compared with comets that arose in our stellar system.

The comet was probably thrown out of its system and flew millions or even billions of years through the interstellar medium. It was first noticed on August 30, 2019 by an amateur astronomer Gennady Borisov during observations at the Crimean Astrophysical Observatory in Bakhchisarai.

Now scientists have studied the isotopic composition of its atmosphere and compared it with comets from the solar system known to science.

It turned out that Borisov’s comet contains an unusually high amount of carbon monoxide. This conclusion was independently reached by the authors of two scientific articles published in the industry publication Nature Astronomy.

First article owned by a team of experts led by NASA staff at the Goddard Space Flight Center in Maryland. For observations, they used ALMA radio telescopes in Chile.

Second – The work of scientists from Auburn University in Alabama who observed the comet with the Hubble Space Telescope and the Swift orbital observatory.

Both groups of researchers found two compounds in the gases released from the comet – hydrogen cyanide (HCN) and carbon monoxide (CO).

Hydrogen cyanide has been observed in the atmosphere of a comet before, and its content in it does not differ from comets in the solar system.

However, the level of carbon monoxide around Borisov’s comet surprised scientists. Astronomers who used the ALMA telescope for their observations suggested that the CO level in this celestial body could be an order of magnitude or even two orders of magnitude higher than in a normal comet (9-26 times).

“For the first time, we were able to peer inside the comet from outside the solar system, and it is strikingly different from most comets we’ve seen before,” says Martin Cordiner from NASA’s Goddard Space Flight Center.

Carbon monoxide is found in most comets. A higher CO content is characteristic of new comets formed in the solar system – but not at the same level as in Borisov’s comet.

However, its concentration varies greatly from comet to comet – and science does not yet know why. This may be partly due to the position of the comet in the star system at the time of its formation.

This may also be due to how often the orbit of a comet leads to its star, thereby causing the evaporation of part of the ice.

If the new data indicate the place of formation of Borisov’s comet, then it’s possible that it formed differently than the comets of the Solar System, which originated in a very cold part of the distant planetary system.

It could be formed from elements with a high ice content of carbon monoxide, which are found only in the coldest parts of the Universe, where the temperature drops below -250 degrees Celsius.

Martin Cordiner from the Goddard Space Flight Center points out that the conditions necessary for the appearance of such a comet are found in protoplanetary disks from which planets form. Many of these discs contain cold gases and dust. The scientist does not exclude that Borisov’s comet could have formed in such conditions.

However, Dennis Bodewitz from Auburn University in Alabama believes that a comet could have appeared near the red dwarf – this is the most common type of star in the Milky Way. These relatively cold stars contain everything needed to form such a comet, Bodewitz said.

The high speed of the comet (33 km / s) may indicate that it was thrown out of its system after close contact with a passing star or a huge planet, astronomers say.

This is the second celestial body of interstellar origin, discovered in the solar system. The first was spotted in 2017 and named 1I / Oumuamua (“scout” or “pioneer” translated from Hawaiian). It was first mistaken for a comet, but after studying the chemical composition, it was classified as an asteroid.

In April, a study was published in the journal Nature Astronomy, the authors of which suggested that Oumuamua could be shard of the planettorn apart by gravity of a star in its system.

–