2I/Borisov, the second observed interstellar visitor (after ʻOumuamua) and first known interstellar comet, is about to reach its closest approach to the sun on December 8, 2019. While astronomers know it’s from another solar system, they don’t know which star exactly. However, a new study has uncovered how 2I/Borisov may have arrived and, in the process, identified two comets in our solar system’s Oort cloud that were highly likely to have been affected or perturbed by nearby stars, which they also identified. Is this fair? Can our Sun perturb some of THEIR comets?
“Since 1950 when Oort published his paper on the structure of the cloud of comets it is believed that stars passing near this hypothetical cometary reservoir play an important role in the dynamical evolution of long period comets and injecting them into the observability region of the Solar System.”
In a new paper accepted for publication in the journal Monthly Notices of the Royal Astronomical Society, Rita Wysoczańska, an astronomer at the Institute Astronomical Observatory at Adam Mickiewicz University in Poland, and fellow Polish astronomers Piotr A. Dybczyński, Małgorzata Królikowska, refute the generally-accepted idea that the Oort Cloud – a shell of space debris around the solar system that is also generally accepted even though it’s still hypothetical – is made up of space rocks flung out there from the birth and early days of our Sun. Instead, they explore the idea that some rocks in the Oort cloud were picked up by the Sun’s gravity – as weak as it is at that distance (about 100,000 astronomical units) – as other stars pass nearby.
Using data from the ESA’s Gaia astronomy spacecraft, which has collected info on over 1.7 billion astronomical objects, they found about 650 that came close enough to perturb a comet into Oort. They compared this to the orbits of 270 long-period comets which can take from 200 years to as long as 30 million years to complete one trip around the Sun. (Hale-Bopp, which passed by Earth in 1997, takes 2,500 years.) Using models to pair stars to comets, they looked for pairs where the star appeared to affect the comet. They found two.
“Anyway we found our results to be the first confirmation of the Oort concept using real stars that make close approaches and significantly change the cometary orbits.”
The pairs were star HD 7977 (constellation Cassiopeia) and comet C/2002 A3, and star Gaia DR2
57002737233036464 (shortened in the paper to Star B) and comet C/2012 F3. Factoring in uncertainties, the team still concluded that these “two comets might have their orbits fundamentally changed due to a close stellar encounter.”
Could this be how 2I/Borisov came to visit our solar system? The report doesn’t answer that question, but …
“We are determined to continue our research on close stellar passages and their influence on LPCs’ dynamical history, still waiting for more numerous and better quality stellar data.”
Once again, astronomy and astrology cross as science confirms that certain nearby stars can affect our Sun and us.