The movements of some-more than 300 000 stars surveyed by ESA’s Gaia satellite exhibit that singular tighten encounters with a Sun competence disquiet a cloud of comets during a apart reaches of a Solar System, promulgation some towards Earth in a apart future.As a Solar System moves by a Galaxy, and as other stars pierce on their possess paths, tighten encounters are unavoidable – yet ‘close’ still means many trillions of kilometres.
Waiting for a stellar encounter
A star, depending on a mass and speed, would need to get within about 60 trillion kilometres before it starts to have an outcome on a Solar System’s apart fountainhead of comets, a Oort Cloud, that is suspicion to extend out to 15 trillion kilometres from a Sun, 100 000 times a Sun–Earth distance.
For comparison, a utmost world Neptune orbits during an normal stretch of about 4.5 billion kilometres, or 30 Sun–Earth distances.
Tracking stellar motions
The gravitational change of stars that pass nearby a Oort Cloud could worry a paths of comets staying there, jarring them onto orbits that move them in to a middle Solar System.
While this is suspicion to be obliged for some of a comets that seem in a skies each hundred to thousand years, it also has a intensity to put comets on a collision march with Earth or other planets.
Understanding a past and destiny motions of stars is a pivotal idea of Gaia as it collects accurate information on stellar positions and motions over a five-year mission. After 14 months, a initial catalog of some-more than a billion stars was recently released, that enclosed a distances and a motions opposite a sky for some-more than dual million stars.
By mixing a new formula with existent information, astronomers began a detailed, large-scale hunt for stars flitting tighten to a Sun.
So far, a motions relations to a Sun of some-more than 300 000 stars have been traced by a Galaxy and their closest proceed dynamic for adult to 5 million years in a past and future.
Of them, 97 stars were found that will pass within 150 trillion kilometres, while 16 come within about 60 trillion km.
While a 16 are deliberate pretty near, a quite tighten confront of one star, Gliese 710, in 1.3 million years’ time, stands out. It is expected to pass within only 2.3 trillion km or about 16 000 Earth–Sun distances, good within a Oort Cloud.
The star is already well-documented, and interjection to a Gaia data, a estimated confront stretch has recently been revised. Previously, there was a 90% grade of certainty that it would come within 3.1–13.6 trillion kilometres. Now, a some-more accurate information advise that it will come within 1.5–3.2 trillion km, with 2.3 trillion km many likely.
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