I’m just passing by? Rogue Star brushed past our solar system very recently

Around 70,000 years ago, a binary star formation skimmed past our solar system – and it could have been visible from Earth.

It’s pretty terrifying that Earth is essentially a cosmic shooting gallery for passing asteroids. But in the grand scheme of things, that’s pretty normal – Earth has survived such impacts in the past, after all. Plus, there are whole stars drifting through space that could have completely ruined our day – and we actually came very close to encountering one recently. If you were looking at the right spot in the sky 70,000 years ago – a time when modern humans were just getting established – you might have spotted a small blazing binary star system as it streaked through the cloud. from Oort.

The Oort cloud, for those unaware, is a spherical cloud of ice-based comets on the outskirts of our solar system, about 100,000 AU from the sun. This binary star system – dubbed Scholz’s Star – passed at a distance of 52,000. In more conventional terms, that’s just 0.8 light-years away. For context, the closest star to Earth (Proxima Centauri) is 4.2 light years away from us.

Scholz’s Star, which is technically a star and a brown dwarf, was spotted about 20 light-years away. It still managed to attract the attention of scientists because it had a very slow tangential motion – which is the language of astronomers for its trajectory in the sky.

“Most nearby stars show much greater tangential motion,” explained Professor Eric Mamajek of the University of Rochester. “The small tangential motion and proximity initially indicated that the star was most likely heading for a future close encounter with the solar system, or that it had ‘recently’ moved closer to the solar system and away from it. Indeed, radial velocity measurements were consistent with it moving away from the vicinity of the Sun – and we realized it must have had a close flyby in the past.

At this distance, Scholz’s star is 50 times fainter than what is usually seen with the naked eye. That said, it is a magnetically active system, meaning it periodically flares up to become thousands times brighter than normal. Our ancestors could very well have spotted it for minutes or even hours at a time when such a searing event occurred. Whether they knew the light was an entire star system is another matter altogether.

Before Scholz’s Star, astronomers predicted that the rogue star HIP 85605 would approach our solar system within the next 240,000 to 470,000 years. However, thanks to new calculations generated from this information, it now appears that HIP 85605 will not even enter the Oort cloud at all. In the meantime, this data will be used to determine which other stars have passed through our solar system recently – and which are still on their way.

Source: The Astrophysical Journal, via the University of Rochester

Arline J. Mercier