There’s a 90 percent chance that a nearby star will be approaching Earth within the next half million years. Known as Hipparcos 85605, the stellar dwarf is currently 16 light years away from us, and it could come as close as 0.13 light years away.
To hunt for close encounters of this stellar kind, Coryn Bailer-Jones of the Max Planck Institute for Astronomy modeled the past and future motion of 50,000 stars using data from the European Space Agency’s Hipparcos satellite, which scanned the sky in the 1990s. He found 14 stars that will be coming within 3.26 light years (that’s one parsec) of the us. And four stars will pass within 1.6 light years (0.5 parsec) of the sun.
Of these, the closest encounter appears to be HIP 85605, which is either a K star (an orange dwarf) or an M star (a red dwarf) in the constellation Hercules. The star has a 90 percent probability of coming between 0.13 and 0.65 light years (0.04-0.20 pc) between 240,000 and 470,000 years from now. The next closest will be Gliese 710 (pictured above), a K7 dwarf that’s about 63 light years away right now in the constellation Ophiucus. This stellar dwarf has a 90 percent probably of coming within 0.32 to 1.44 light years (0.10-0.44 pc) in about 1.3 million years.
While HIP 85605 and GL 710 pose no direct collision danger, their gravitational forces could, however, scatter comets out of the Oort Cloud in our outer solar system -- sending them careening inwards in our direction. "I think we can safely predict that comet orbits would indeed be disrupted by the closest encounters," Bailer-Jones tells New Scientist. He’ll be following-up with the probability of Earth being hit by a comet strewn by a passing star. A larger perturbation may have been caused by gamma Microscopii, he writes, a G6 giant that came within 1.14 to 4.37 light years (0.35-1.34 pc) around 3.8 million years ago.
And will any of these stars bring along their pack of exoplanets? Likely, but they won’t be close enough for us to visit. According to Bailer-Jones, their fast speed as they swing by the sun would make reaching those planets as difficult as traveling to more distant star systems.
He also cautions that some of the stars simulated have “questionable data,” so these estimations could be slightly off. “This study is limited to stars for which we have accurate distances and velocities; which, in turn, limits us to stars currently within a few tens of [light years] from the Sun,” Bailer-Jones tells Forbes. His calculations show that 42 stars have or will come within an estimated 6.4 light years (2 pc) of the sun over a time-frame spanning 20 million years in our past to 20 million years in the future.
The work will appear in Astronomy & Astrophysics, and it’s available online at arXiv now.
Image via NASA APOD