Currently, Alpha Centauri is the closest star to our Sun, at a distance of four light-years. But about 70,000 years ago, an interstellar interloper brushed past less than a light-year from us, making it the closest recorded pass of another star. A new study has found that the effects of this close encounter are still felt today, as the orbits of hundreds of comets and asteroids still bear the star's gravitational influence.
WISE 0720−0846, better known by the nickname Scholz's Star, is a binary red dwarf/brown dwarf system that's currently about 20 light-years away. But around the time that modern humans were first migrating out of Africa, it swung past our neighborhood at the incredibly close distance of 0.8 light-years. That means its trip would have taken it through the Oort Cloud, the swarm of icy objects that surrounds the Solar System, and its visit wouldn't have gone unnoticed by the locals.
Now, researchers from Cambridge and the Complutense University of Madrid have calculated those effects on the asteroids and comets that would have called the Oort Cloud home. The most likely candidates to still carry the mark of Scholz's Star are those with hyperbolic orbits that take them on extremely long journeys between the inner and outer Solar System. On studying almost 340 objects with this kind of trajectory, the researchers found that many of them seem to originate from the same area – near where the star passed.
"Using numerical simulations we have calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come," says Carlos de la Fuente Marcos, co-author of the study. "In principle, one would expect those positions to be evenly distributed in the sky, particularly if these objects come from the Oort cloud; however, what we find is very different: a statistically significant accumulation of radiants. The pronounced over-density appears projected in the direction of the constellation of Gemini, which fits the close encounter with Scholz's Star."
The team says that the find could be a coincidence, but that seems unlikely since it lines up both in space and time. Interestingly, the team's simulations suggest the star's trek might have brought it even closer than previously thought, to within 0.6 light-years of the Sun.
The research was published in the journal MNRAS Letters.
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