This has been discovered in August 2019, but the interstellar comet 2I/Borisov was already found inside the Solar System at that point. After taking a look at all the data they gathered, astronomers found the object, which appeared in images from December 2018. The distance of the comet when it was discovered was three astronomical units from the Sun, that’s about twice the distance of Mars’ average orbit. The farthest distance that we can see is eight astronomical units, which is past the planet Jupiter.
This discovery will help us in understanding the properties of the interstellar visitor, and we can better calculate its trajectory. The research has been published in The Astronomical Journal. 2I/Borisov was in something we call solar avoidance zone before its discovery.
Scientists Knew About The Interstellar Comet Long Before It Was Actually Discovered
This particular region of the sky is too close to the Sun to give us clean observations because solar radiation creates too much noise, a thing that can damage the signal. The radiation of the Sun can also damage some of the instruments. This zone is avoided, and 2I/Borisov was there between May and September 2019., so we really had no choice.
A team of scientists, led by Quanzhi Ye from the University of Maryland, has taken a look at the data collected by the Catalina Sky Survey, the Zwicky Transient Facility, and Pan-STARRS to see if they caught something of the comet. All the sky time surveys, which search the skies to find changes in some cosmic objects, are looking at skies when objects are not there. And because they were made to find unusual objects, they’re really good at detecting objects before they are actually officially discovered.