Scientists have discovered that 1.3 million years from now a star will brush past our solar system, potentially sending a huge mass of comets hurtling towards Earth.
The star, Gliese 710, will come within 1.4 trillion miles of our sun—well within the Oort Cloud, a huge shell of icy objects surrounding the solar system and extends around 9.3 trillion miles. When it gets this close, the gravitational force of the star has the potential to disrupt this body of comets, the impact of which could be catastrophic for the inner solar system planets.
The discovery of this forthcoming close encounter was made by looking at the past and future trajectories of 320,000 stars in the Milky Way. Coryn Bailer-Jones, from the European Space Agency, used data from the ESA’s Gaia Mission—a project to create a 3D map of the Milky Way, surveying over 1,000 million stars in the process. He combined this data with existing information, he was able to find the stars that will come closest to use over the next five million years.
His findings, published in Astronomy & Astrophysics, show that there are 16 stars that will come within two parsecs (one parsec is equivalent to around 19 trillion miles) of the sun over the next five million years. He found 97 stars that come within 93 trillion miles of the sun. To exert an influence over the Oort Cloud, it is estimated a star would need to come within 37 trillion miles.
Of the 16 closest—a few of which Bailer-Jones acknowledges have “dubious data”—Gisele 710 will come closest.
This star, the ESA notes, has a mass of around 60 percent of our sun and is travelling very slowly—around half the speed of most stars in our galaxy. This will give it plenty of time disrupt the Oort Cloud, possibly sending comets hurtling towards us.
Overall, Bailer-Jones estimates that over the past five million years, and five millions years into the future, the average rate of a stellar close encounter is one every 50,000 years. “It is important to note that it is not guaranteed that a star would actually perturb any comets such that they entered the inner regions of the Solar System, and even if they did, if Earth would be in the firing line,” the ESA said in a statement.
While the risk of Gisele 710 poses to Earth is unclear, we do know that in about four billion years, the Milky Way will collide with our neighboring galaxy Andromeda. When this happens the consequences will be catastrophic, throwing both into disarray and eventually leading to the formation of one, giant hybrid galaxy.