Less than 100,000 years ago, a cool, small star flew within 0.8 light years of our sun, brushing past the icy Oort cloud that lies at the outer edges of our solar system, according to research published this week.
Scientists say it is the closest a known star has ever come to our planet in the recent past.
The stellar encounter likely took place about 70,000 years ago, researchers said in a paper in Astrophysical Journal Letters.
In a study led by Eric Mamajeck of the University of Rochester, astronomers ran 10,000 simulations of possible paths the star could have taken as it flew past our solar system. Ninety-eight percent of them take it through the Oort cloud, the scientists reported.
Although the fly-by was particularly close in astronomical terms, the researcher said, it was not necessarily dramatic.
The star, nicknamed Scholz's star after the German astronomer Ralf-Dieter Scholz who discovered it, is a dim red dwarf that is currently about 20 light years from our planet.
Its mass is just 8% that of our sun, and it is so faint that even at the time of its closest approach to our solar system, it would need to be 50 times brighter to be observed with the naked eye.
It would not have put on a dazzling light show on Earth, and the scientists said it likely did not have much of an effect on the comets in the Oort cloud either.
Mamajeck said this result is not surprising. He noted that stars pass through the Oort cloud "all the time" -- about 10 stars every million years. However, very few of them are massive or slow-moving enough or come close enough to produce any significant effect on the comets in the Oort cloud, he said in a statement.
He also said he expects that the European Space Agency's Gaia mission, which aims to make a 3-D catalog of 1 billion stars may reveal other stars that have come closer to our sun than Scholz's star.
It might also reveal stars that will come close to the sun in the future, he said.