A comet that entered our solar system from interstellar space may never return. Material eruptions were observed in comet 2I / Borisov as it moved away from the Sun.
These outbursts indicate that the comet is disintegrating, according to Polish astronomers at the Jagiellonian University in Krakow and the University of Warsaw, who recorded this activity.
“This behavior is compelling evidence of ongoing core fragmentation,” they wrote in a notice posted to Astronomers Telegram.
2I / Borisov first came to the attention of the world at the end of August last year, when it was discovered sweeping through the solar system on a trajectory indicating an interstellar origin.
Scientists later decoded the observations and found images of the comet dating back to December 2018. These numerous additional data support conclusions about the comet's interstellar origin and allow more accurate predictions of its future trajectory.
What astronomers especially wanted to see was what happened after the comet reached perihelion – its approach to the Sun – on December 8, 2019.
This is because there are two types of comets in the solar system. Short-period comets usually come from the Kuiper belt or closer and have an orbital period of less than 200 years. They are much more likely to remain intact when they pass the Sun.
Long-period or dynamically new comets come from afar – the Oort cloud – and are more likely than short-period comets to decay. Analysis of the color and composition of 2I / Borisov showed that it is very similar to comets with a long period, therefore decay due to heating from the Sun was expected, but not guaranteed.
“For comets in the solar system, dynamically new comets are known to be 10 times more likely to disintegrate than short-period comets, probably due to their original state and weaker structural strength,” wrote the researchers led by Quanzhi Ye from University of Maryland.
This would be seen as a change in brightness in the comet – and indeed, this is what was observed, from 5 to 9 March 2020, the comet flashed twice. As the comet decays, observations of its spectrum will reveal its internal chemistry, including its core.
This is a great opportunity to study the inner structure of a comet and compare it with comets in our solar system to see how similar or different they are.
Therefore, astronomers will continue to closely monitor 2I / Borisov.
