A recently discovered nearby binary star system has been tracked backwards to a near collision with our own Solar System, astronomers are saying. The pair came so close they grazed the outer edge of the Solar System, skimming that comet-heavy belt of objects known as the Oort Cloud. In fact, the stellar duo are now believed to be the closest any alien stars have ever come to our own.
Phys.org reported Feb. 17 that Sholz’s Star and its companion passed through the Solar System about 70,000 years ago at a distance of 0.8 light years, a relatively short distance in space terms. It equates to a mere 5 trillion miles and less than a fifth of the span between Earth’s Sol and the nearest star, Alpha Proxima, which is 4.2 light years away.
Eric Mamajek from the University of Rochester and Valentin D. Ivanov of the European Southern Observatory authored the paper (published in the Astrophysical Journal Letters) after studying the low-mass red dwarf star and its brown dwarf companion. They first became interested in Sholz’s Star when they discussed its slow tangential motion across the sky. Closer examination of the stars, which are only about 20 light years away, indicated that the slow tangential motion was due to the binary star system’s nearly straight trajectory away from our Solar System. And they were moving at a tremendous speed as well.
To determine just how close Sholz’s Star actually came to the Solar System, Mamajek employed the help of former University of Rochester undergraduate Scott Barenfeld (now a Caltech graduate student) to construct simulations of the star’s fly-by. Barenfeld projected 10,000 orbits, with 98 percent indicating that the binary stars passed through the outer Solar System’s Oort Cloud. Only one showed the stars passing through the inner Oort Cloud (something that would have set off a cometary showers).
Mamajek told BBC News that the effects of Sholz’s star’s fly-by were likely “negligible,” but of the trillions of objects in the Oort Cloud, it was liley “some of them were perturbed by this object.” He added, “But so far it seems unlikely that this star actually triggered a significant ‘comet shower’.”
It is as yet unknown just how many rogue stars there are in the Milky Way, or just how many might be headed toward our Solar System, but Mamajek noted that fly-bys like that of Sholz’s Star occur about every 100,000 years. A study published last year indicated that most rogue stars could be found in the vast regions between galaxies, concluding that about half of all stars in the universe existed outside of galaxies as rogue stars.
The closest star fly-by previously calculated by astronomers was that of rogue star (a star gravitationally independent of other star systems, groups, or galaxies) HIP 85605, which is set to pass relatively near in some 240,000 to 470,000 years. And by “relatively,” it is meant that said rogue star will pass some 200 light years distant when it finally enters our stellar neighborhood.
Sholz’s Star is currently flying away from the Solar System and located in the constellation Monoceros. The researchers found that it is a magnetically active star as well, which means that when it made its fly-by 70,000 years ago, it might have been seen by humans due to such stars’ ability to emit sustained flares that would have been visible to the naked eye.
Sholz’s Star was discovered by astronomer Ralf-Dieter Scholz of the Leibniz-Institut für Astrophysik Potsdam (AIP) in Germany in 2013. The binary star system is just one of the many billions of stars mapped by NASA’s Wide-field Infrared Survey Explorer (WISE) mission.