On August 30th, amateur astronomer Gennady Borisov spotted a comet of extrasolar origin passing through our Solar System. This is the second time in as many years that an interstellar object has been observed (the last being ‘Oumuamua 2.0 in 2017). Thanks to the Gemini Observatory, we now have pictures of this comet, making it the first object of its kind to be successfully imaged in multiple colors!

The comet, designated C/2019 Q4 (Borisov), was captured by the Gemini North Telescope’s Gemini Multi-Object Spectrograph on the night of September 9-10th. The image showed a very pronounced tail, which is indicative of outgassing and confirms that the object is a comet. This is another first, where C/2019 Q4 is the first interstellar visitor to clearly form a tail as a result of outgassing.

Artist’s impression of the interstellar object, `Oumuamua, experiencing outgassing as it leaves our Solar System. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser

Andrew Stephens, an astronomer with the Gemini Observatory, was responsible for coordinating the observations. As he explained:

“This image was possible because of Gemini’s ability to rapidly adjust observations and observe objects like this, which have very short windows of visibility. However, we really had to scramble for this one since we got the final details at 3:00 am and were observing it by 4:45!”

The color image was produced by combining the Gemini observations, which were taken in two color bands. These were obtained as part of a project led by Piotr Guzik and Michal Drahus at the Jagiellonian University in Krakow (Poland), which seeks to capture images of astronomical “targets of opportunity”.

At present, C/2019 Q4 is close to the apparent position of the Sun and is therefore difficult to observe. Over the next few months, its hyperbolic flight path will bring it to more favorable observing conditions. It is this same path that led astronomers to conclude that it is likely to be interstellar in origin, and follow-up observations are expected to reveal more about its composition.

Artist’s impression of the first interstellar asteroid/comet, “Oumuamua”. This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser

Since asteroids and comets are believed to be leftover material from the formation of a system, knowing what this comet is composed of will allow astronomers to learn a great deal about where it came from. This is one of the greatest benefits of interstellar objects, in that they allow us to learn more about distant star systems without actually having to send robotic spacecraft there.

In the case of C/2019 Q4, astronomers also have the benefit of knowing about it in advance. When ‘Oumuamua was first detected, it had already made its closest pass to the Sun and flew by Earth on its way out of the Solar System. In other words, the most opportune times to study it had largely passed by the time it was spotted.

And if there is even the slightest chance that this interstellar visitor is an extra-terrestrial probe (as was suggested about ‘Oumuamua), then future studies will reveal far more than we ever expected! But let’s not get ahead of ourselves here…

Further Reading: Gemini Observatory