Recently-discovered comet to pass Earth in December

BY MAEVE BRADY ’20

A traveler from another star, a comet named 2I/ Borisov, was identified this past summer by Crimean amateur astronomer Gennady Borisov. 2I/Borisov will reach the closest point to the sun in its trajectory, its perihelion, on Dec. 7. at a distance of about 180 million miles, and will be closest to Earth on Dec. 29.

Borisov spotted the interstellar object through his homemade two-foot telescope. The comet appeared as a blurry blob of light cruising through the constellation Cancer and looked like it was moving too fast — about 20 miles per second—to be captured by the sun’s gravity, which made it unlikely that this object was in orbit around the sun.

2I/Borisov has been confirmed as an interstellar object; its velocity is much higher than what is typical of objects orbiting the sun at that distance, which is indicative that it came from outside our solar system and will eventually depart from it as well.

This comet is actually the second interstellar object that we have detected. The first, 1I/Oumuamua, was discovered in 2017, when its tour through our solar system was already coming to an end. The fact that 2I/ Borisov is currently inbound has stirred up great excitement among astronomers, as it means that there will be much more time to gain information from this visitor than there was from 1I/Oumuamua. Additionally, 2I/Borisov is bigger and brighter than its predecessor, which gives astronomers more to work with as they study its light and composition and make the most of this rare opportunity.

“We’re very interested in the formation of planetary bodies around other stars,” Professor Jason Young of the Mount Holyoke astronomy department. “One of the first things they did, in the couple of days after they discovered [2I/Borisov], was ask the question, ‘could we send a spacecraft to visit it?’”

Being able to send a spacecraft to intercept the comet could be invaluable in terms of the information it would provide, but it may not be practical right now.

According to Professor Young, “the last convenient launch date would have been in 2018, so the easy window has passed.” Instead, focus has shifted to the future.

“There’s more of a sense now that [interstellar objects] might be more common than we realized,” Professor Young explained. “So maybe a better strategy is to be prepared for the next one, [and] have a vehicle sitting on the launch pad.”

Pending the arrival of a new interstellar visitor, astronomers are trying to glean as much as they can from 2I/Borisov while it passes through our solar system. The International Astronomical Union’s September press release on the topic expressed excitement at the discovery of not just one, but now two interstellar objects within a two-year span. This frequency suggests the thrilling possibility that we may soon identify more of these objects for observation and the data we gather could grant us new insight into planetary systems far beyond our own.