Stunning images of Interstellar visitor captured by Hubble

The Hubble Space Telescope has captured stunning images of the Comet 2I/Borisov — believed to be a visitor from outside the solar system.

On 12 October 2019, the NASA/ESA Hubble Space Telescope observed Comet 2I/Borisov at a distance of approximately 420 million kilometres from Earth. The comet is believed to have arrived here from another planetary system elsewhere in our galaxy ( NASA, ESA, D. Jewitt (UCLA))

The Hubble Space Telescope has granted astronomers their first good look at Comet 2I/Borisov — a fairly unique object, as there is good reason to believe it arrived in our solar system from elsewhere in the galaxy.

The images — made as part of DD Program #16009 — provide the clearest view of the interstellar object thus far, clear enough to reveal a concentration of dust around its nucleus of solid ice. Comet 2I/Borisov is the second known interstellar object to intrude our solar system. The first, an object known as ‘Oumuamua, passed within 38 million kilometres of the Sun in 2017 before exiting the solar system.

Despite their common extrasolar origins, ‘Oumuamua and Comet 2I/Borisov are fundamentally different as David Jewitt of UCLA, leader of the Hubble team who observed the comet, explains: “Whereas ‘Oumuamua looked like a bare rock, Borisov is really active, more like a normal comet.

“It’s a puzzle why these two are so different.”

The comet offers unique opportunities for researchers to investigate the chemical composition of the dust and gas that form the building blocks of planets elsewhere in the galaxy. From there they can compare the similarities and differences of planets formed in our solar system and those forged elsewhere in the Milky Way.

On 12 October 2019, the NASA/ESA Hubble Space Telescope observed Comet 2I/Borisov at a distance of approximately 420 million kilometres from Earth. The comet is believed to have arrived here from another planetary system elsewhere in our galaxy. (NASA, ESA, D. Jewitt (UCLA).)

Amaya Moro-Martin of the Space Telescope Science Institute in Baltimore, Maryland, comments: “Because another star system could be quite different from our own, the comet could have experienced significant changes during its long interstellar journey.

“Yet its properties are very similar to those of the Solar System’s building blocks, and this is very remarkable.”

Comet 2I/Borisov was identified following a week of observations by both amateur and professional astronomers after it was first spotted on 30th August 2019 by Crimean amateur astronomer Gennady Borisov.

The orbit calculated for the comet by the International Astronomical Union’s Minor Planet Center revealed its origins lay outside the solar system. Until now, all catalogued comets have originated from the Kuiper belt — a ring of icy debris that lies beyond Neptune— or from the Oort cloud — a shell-like collection of icy objects in the very outermost region of the solar system.

This illustration shows the path of comet 21/Borisov through our Solar System. This visitor came from interstellar space along a hyperbolic trajectory. It is only the second known intruder to zoom through our Solar System (the interstellar object ‘Oumuamua was detected in 2017). As the graphic shows, the comet’s straight path across interstellar space is slightly deflected by the gravitational pull of our Sun. The comet is travelling so fast, at over 155 000 kilometres per hour, it will eventually leave the Solar System. The panel on the right shows the comet’s position relative to Earth when the NASA/ESA Hubble Space Telescope observed it on 12 October 2019, when it was 420 million kilometres from Earth.(NASA, ESA, J. Olmsted, F. Summers (STScI).)

The comet was snapped by Hubble at a distance of 420 million kilometres from Earth whilst travelling towards the Sun in a hyperbolic arc. Travelling with a tremendous velocity of 1.5 x 10⁵ km/h, Comet 2I/Borisov will make its closest approach on the 7th of December. At this point, it will be at a distance from the Sun that is twice that of the Earth’s.

By mid-2020 it will make its way out of our solar system and back into interstellar space — drifting for millions of years until an encounter with another solar system. This means that astronomers will have to act quickly to investigate it further, with future investigations planned for January 2020.

But even if this opportunity isn’t fully realised, astronomers will take heart in the fact that both ‘Oumuamua and Comet 2I/Borisov are very likely just the tip of an interstellar iceberg in terms of objects briefly intruding into our solar system.

Observations by Hubble — amongst other telescopes — have revealed rings and shells of icy debris are common around young stars during the period of planet formation. Gravitational interactions between these icy objects and other massive bodies have the potential to send them hurtling through space as comets.

In fact, thousands of such objects could be passing through the solar system at any given time — with most being too faint to spot with our current generation of telescopes.