About 70,000 years ago, a red dwarf star came within one light-year of our Solar System. And it turns out we can still see some of the results of that close passage.
Called Scholz’s star, it passed less than a light-year from our Sun, the closest passage of a star we know about. This was near enough to disturb the Oort Cloud, a huge mass of trillions of comets that surrounds our Solar System out to about several light-years.
And a team of astronomers from the Complutense University of Madrid and the University of Cambridge have found dozens of comets in our Solar System that appear to have been disturbed by this star. Their findings are published in the journal Monthly Notices of the Royal Astronomical Society: Letters.
These comets are in V-shaped hyperbolic orbits, with their paths extending far out of the Solar System before swinging in again. Studying the known orbits of these objects, of which there were 339 in total, the team worked out that 36 seem to have been affected by the passing star.
"Some of them seem to be coming from the same region in the sky (an area on Gemini) that appears to have been crossed by the Scholz's star nearly 70,000 years ago," Carlos de la Fuente Marcos from Complutense University, the study's lead author, told IFLScience.
The star has just 9 percent of the Sun's mass, and is now located about 20 light-years from our Solar System. But that’s still a decent size, and its close proximity meant it sent our Oort Cloud haywire. It’s even possible that our distant ancestors saw its faint reddish light in the night sky.
Back in 2015 researchers first discovered that Scholz’s star, which is thought to actually be part of a binary system, passed our Solar System. It’s important to see the impact it had, not least because we think another star – Gliese 710 – may pass quite close in about 1.35 million years.
Interestingly, there’s another significant finding hidden in this latest study. The researchers also said that they had found evidence for eight comets that could be interstellar objects, one of which – C/1999 U2 – is still in the Solar System today. It's tough to know for sure as we haven't seen it again since 2005, although it's possible that another body (C/2005 W5) is the same object.
You may remember ‘Oumuamua, the first interstellar visitor ever seen in our Solar System, was spotted last year. But astronomers have thought there could be more, and this study appears to suggest that’s the case.
“Interstellar interlopers could be the result of the gravitational slingshot effect,” the researchers note in their paper. “The prospect of detecting these bodies has been considered for decades.”