Our solar system is located about 2/3rds of the way from our galactic center, in the Orion spur (of the Perseus spiral arm), which is relatively empty compared to the more cluttered area surrounding the super-massive black hole situated at the center of the Milky Way. However, that’s not to say that no stars or celestial objects pose a danger to us here on Earth. In fact, one particular star may actually pose a significant danger to us. New models uncovered in 2010 say that a rogue star could seriously upset the icy comets in the Oort cloud, a theoretical region located on the fringe of our solar system.
The star, tentatively known as Gliese 710, is an orange dwarf star currently located some 63.8 light-years from Earth in Serpens constellation. The star is relatively unremarkable, coming in with only 60% of the sun’s total mass (or about 67% of the sun’s radius), but recent simulations, undertaken by Vadim Bobylev (from the Pulkovo Astronomical Observatory in St Petersburg) believe it could have a remarkable impact on us. Recently, astronomers were working on the Hipparcos Catalog, which aimed to collect data (such as the position, velocity and trajectory) of the 100,000 stars located in the vicinity of the sun, initially found 156 stars that could dwell a little bit too close for comfort.
Whilst uncommon, it’s not unheard of for stars to make an appearance on the outer end of a planetary system. It’s just in this case, we find that the solar system in question is ours. In fact, it’s estimated that once every 2 million years, a rogue star arrives in our galactic neighborhood (defined by an area extending about 1 parsec [31 trillion kilometers/19 trillion miles] or 3.26 light-years of the sun). The last of which, Gliese 208, passed within four light years of us about half a million years ago. But to suss these stars out in advance, many variables must be considered (and lots of data painstakingly sorted through). So Bobylev did just that by taking a look at the latest data collected by Hipparcos to recalculate the likelihood of a collision. What he found was (by his own admission) “shocking.”
First, the 156 stars estimate was way off base. Instead, only 9 may actually fall into the “dangerous” category. But with Gliese 710, he estimated that there is an 86% chance of a that the star will come as close to us as about half a parsec (the outer boundary of our solar system), which is home to millions of comets. Of course, the area we are talking about is substantially large and quite a way away from Earth, meaning none of our planets are in danger of colliding with the star, but a gravitational perturbation could very well dislodge a large number of comets located in the Oort Cloud, which could in turn bombard our planet with icy balls of death. (Ask the dinosaurs… oh wait. Too soon?)
According to Bobulev, “86 percent is about as close to certainty as this kind of data can get.” . Plus, there is an even smaller chance (about 1 in 1000) that G170 will come any closer to Earth than the asteroid belt, so we need not worry too much about it. Besides, a lot can happen in 1.5 million years!
You can read the full paper “Searching for Stars Closely Encountering with the Solar System” here.