On October 12, 2019, the NASA/ESA Hubble Space Telescope provided astronomers with their best look yet at the first confirmed interstellar comet – the 2I/Borisov (originally designated C/2019 Q4).

It was given the “2I” designation, where “I” stands for interstellar. It is the second observed interstellar interloper after 1I/‘Oumuamua.

The 2I/Borisov, which astronomers believe to have arrived here from another planetary system elsewhere in our galaxy, will make its closest approach on December 8, 2019.

At the time the images were taken, the Borisov was 260 million miles (418 million km) from Earth. It will never get closer than 190 million miles (305 million km, a little more than twice the distance between the Earth and Sun – 2 AU – Astronomical Unit) from us but will be visible long enough for a lot more analysis.

The comet was named after its discoverer, Gennady Borisov, the Crimean astronomer and veteran comet hunter at the Crimean Astrophysical Observatory. Borisov discovered C/2019 Q4 on August 30, 2019, using his custom-built 0.65-meter telescope.

NASA’s Hubble Space Telescope has given astronomers their best look yet at an interstellar visitor – Comet 2I/Borisov – whose speed and trajectory indicate it is from outside of our solar system. This Hubble image, taken on October 12, is the sharpest ever view of the comet. Hubble reveals a central concentration of dust around the solid icy nucleus. For more information, visit: https://nasa.gov/hubble
Credit: NASA’s Goddard Space Flight Center
Paul R. Morris (USRA): Lead Producer
Music Credits: “Solar Pilgrims” by Francois Vey [ SACEM ] Universal Production Music

The Borisov comet is following a hyperbolic path around the Sun. It is currently blazing along at an extraordinary speed of 110,000 miles per hour (177,000 km/h or 49 km/s).

David Jewitt of the University of California, Los Angeles (UCLA), leader of the Hubble team who observed the comet, said: “It’s traveling so fast it almost doesn’t care that the Sun is there”.

It is way faster than ʻOumuamua, the first known interstellar object detected passing through the Solar System, which has a speed of 26.33 km/s.

Based on the early observed characteristics and its hyperbolic orbit and extraordinary speed aside, 2I/Borisov appears indistinguishable from the native Solar System comets.

Hubble image of 2I/Borisov
Hubble image of 2I/Borisov, originally designated C/2019 Q4 (Borisov), and popularly known as the Borisoc comet, the first observed interstellar comet, and the second observed interstellar interloper after ʻOumuamua. This image was acquired by the Hubble Space Telescope on October 12, 2019.

According to the Hubble Space Telescope website, future Hubble observations of 2I/Borisov are planned through January 2020, with more being proposed.

According to NASA, the comet will streak past Jupiter’s distance of 500 million miles (800 million km) on its way back into interstellar space by the middle of 2020.

There it will drift for untold millions of years before skirting close to another star system.

It seems the interstellar objects entering the solar system are not rare at all. Researchers think Borisov and ‘Oumuamua are only the beginning of the discoveries of interstellar objects paying a brief visit to our solar system.

In fact, there are thousands of such “visitors” here at any given time. But most of them are too faint to be detected with current-day telescopes.


M. Özgür Nevres

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