It was magnetically active, producing flares that make a star appear thousands of times brighter
An international team of astronomers has identified the closest known encounter of a star to our solar system. Researchers led by Eric Mamajek of the University of Rochester said Tuesday that a red dwarf star and its brown dwarf companion passed through our solar system’s Oort Cloud about 70,000 years ago. Oort Cloud is a region at the outer edge of our solar system, filled with trillions of comets.
Our ancestors might have seen Scholz’s star with the naked eye
The rogue star is named WISE J072003.20-084651.2 or Scholz’s star after its discoverer. Findings of the study were published in the latest issue of The Astrophysical Journal Letters. Scholz’s star’s trajectory suggests that it passed just 0.8 light years (52,000 astronomical units or 5 trillion miles) from the solar system about 70,000 years ago.
It may seem like a huge distance, but it’s very close astronomically. No other known star has ever approached our solar system this close. By comparison, our closest neighbor star Proxima Centauri is located 4.2 light years away. After missing our solar system by a small distance, Scholz’s star is still traveling. It’s now 20 light years away in the Monoceros constellation.
At its closest encounter, Scholz’s star was only a 10th magnitude star, meaning it could not be seen with the naked eye at night. However, it was magnetically active, producing flares that make a star appear thousands of times brighter. So, it’s possible that our ancestors in Africa might have seen it during the rare flaring events 70,000 years ago.
Scholz’s star passed through the Oort Cloud
Lead author Eric Mamajek said that most stars this close show much larger tangential motion. Scholz’s star’s proximity and small tangential motion suggested that it either “recently” had a close encounter and was moving away, or moving towards a future close flyby. Researchers studied its speed and current direction and then worked backwards to find that it must have passed through the Oort Cloud.
Mamajek said its radical velocity measurements revealed that Scholz’s star was moving away from our solar system, so it must have had a close encounter in the past. Researchers studied its radical velocity and tangential velocity using spectrographs on telescopes in Chile and South Africa.