A star known as Gliese 710 is headed for a close encounter with our star Sol.
Gliese 710 is a star in the constellation Serpens Cauda which is expected to pass through our Solar System’s Oort cloud 1.35 million years from now. Its distance at closest approach is expected to be about 13000 astronomical units, or a mere 77 light days (430 times the orbit of Neptune),[note 4]. For comparison, Proxima Centauri is more than 1500 light days away.
The movements of more than 300 000 stars surveyed by ESA’s Gaia satellite reveal that rare close encounters with our Sun might disturb the cloud of comets at the far reaches of our Solar System, sending some towards Earth in the distant future.
As the Solar System moves through the Galaxy, and as other stars move on their own paths, close encounters are inevitable – though ‘close’ still means many trillions of kilometres.
The unassuming star centered in this sky view will one day be our next door stellar neighbor.
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Credit: Digitized Sky Survey, SkyView
A star, depending on its mass and speed, would need to get within about 60 trillion kilometres before it starts to have an effect on the Solar System’s distant reservoir of comets, the Oort Cloud, which is thought to extend out to 15 trillion kilometres from the Sun, 100 000 times the Sun–Earth distance.
An artist’s rendering of the Oort cloud and the Kuiper belt
Credit: NASA
For comparison, the outermost planet Neptune orbits at an average distance of about 4.5 billion kilometres, or 30 Sun–Earth distances.
The gravitational influence of stars that pass near the Oort Cloud could perturb the paths of comets residing there, jolting them onto orbits that bring them in to the inner Solar System.
While this is thought to be responsible for some of the comets that appear in our skies every hundred to thousand years, it also has the potential to put comets on a collision course with Earth or other planet
Tracking stellar motions
A view of a small part of the sky as if you were staring at a star (centre) approaching nearly head on, and then as it passes by and away again.
The motion can be likened to what an observer standing beside a road would see looking at an approaching car, and then swinging around to continue to follow it as it moves away. As a result, the objects in the background – in this case distant stars – become blurred as you move quickly to maintain a visual on the passing object.
The focus of this animation is the star known as Gliese 710. It will have a close encounter with our Sun in 1.3 million years, passing within the Oort Cloud reservoir of comets in the outskirts of our Solar System. The star is predicted to pass within about 2.3 trillion kilometres, the equivalent of about 16 000 Earth–Sun distances. The star’s motion is set against a background of other moving stars and the visualisation covers, very quickly, the timeframe from about 1.1–1.5 million years in the future.
Credit: Copyright ESA/Gaia/DPAC
The size of the field of view is 10 x 5º (for comparison: the Moon spans 0.5º on the sky) and the colours represent the astronomical colours of the stars as derived from the Gaia data. Gliese 710 is an orange K-type dwarf star, an ordinary star similar to the Sun but less hot and less massive..
Understanding the past and future motions of stars is a key goal of Gaia as it collects precise data on stellar positions and motions over its five-year mission. After 14 months, the first catalogue of more than a billion stars was recently released, which included the distances and the motions across the sky for more than two million stars.
By combining the new results with existing information, astronomers began a detailed, large-scale search for stars passing close to our Sun.
So far, the motions relative to the Sun of more than 300 000 stars have been traced through the Galaxy and their closest approach determined for up to five million years in the 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 the 16 are considered reasonably near, a particularly close encounter of one star, Gliese 710, in 1.3 million years’ time, stands out. It is predicted to pass within just 2.3 trillion km or about 16 000 Earth–Sun distances, well within the Oort Cloud.
The star is already well-documented, and thanks to the Gaia data, the estimated encounter distance has recently been revised. Previously, there was a 90% degree of certainty that it would come within 3.1–13.6 trillion kilometres. Now, the more accurate data suggest that it will come within 1.5–3.2 trillion km, with 2.3 trillion km most likely.
Edited by
mightymoe
on Sun 09/03/17 09:55 AM