Second Interstellar Visitor is Surprisingly Similar to Comets in Solar System: Study – The Weather Channel

Gemini Observatory two-color composite image of 2I/Borisov

Two years ago, on October 19, 2017, a mysterious, elongated, dark-red object was detected in our solar system cruising at around 315,364 km per hour. After several months of research, scientists suggested that it may even be an alien probe investigating our solar system. It was named Oumuamua, which roughly translates to "visitor from afar, arriving first" in Hawaiian. It was only July 2019 that scientists confirmed that Oumuamua has a purely natural origin.

On August 30, 2019, amateur astronomer Gennady Borisov spotted another mysterious object, brighter than Oumuamua. After thorough analysis, the International Astronomical Union confirmed on September 24 that the object has a highly open orbit (with no specified return to a specific angular position). The union named the object 2I/Borisov, confirming that it is the only second interstellar (travelling from or originating in other star-systems) object identified in our solar system.

Now, European astronomers have described the characteristics of the newly identified interstellar comet, 2I/Borisov in a paper published in Nature Astronomy. The findings suggest that, despite its faraway origin, the new comet has strikingly similar colour and structure to that of any active comet in our solar system. Oumuamua, on the other hand, had unusually elongated shape along with the absence of cometary activity.

"Images taken on 10 and 13 September 2019 UT with the William Herschel Telescope and Gemini North Telescope show an extended coma and a faint, broad tail," write the authors, who add that the nucleus is probably around one kilometre in radius, which is common with Solar System comets.

"Based on these early characteristics, and putting its hyperbolic orbit aside, 2I/Borisov appears indistinguishable from the native Solar System comets," the study says.

A comet is usually a cold, icy celestial body which starts to release gasses upon approaching any star. The defining characteristic for any comet is the long outgassing tail. While the tail can be observed very clearly in case of 2I/Borisov, Oumuamua showed no obvious signs of outgassing. Scientists believe that more such interstellar objects might have entered our solar system in the past, but we haven't been able to spot them either due to small size or lack of technology.

The study says that since 2I/Borisov was discovered while it was approaching the Sun, astronomers will be able to acquire more data before it passes in approximately a year from now. The scientists say that the closest encounter is expected on December 8, 2019.