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from the where-close-is-measured-in-kiloAUs dept.
The European Space Agency (ESA) is reporting on some early results of its Gaia mission. Close approaches of our solar system by other stars could disrupt the orbits of objects in the Oort cloud causing some of them to hurtle sunward.
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 [1 million AU], while 16 come within about 60 trillion km [400 thousand AU].
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.
The report The completeness-corrected rate of stellar encounters with the Sun from the first Gaia data release was published in Astronomy & Astrophysics. DOI: https://doi.org/10.1051/0004-6361/201731453 PDF (2.26 MB)
[Note: 1 Astronomical Unit ~ 150 million Kilometers]
I find it fascinating that, in astronomy, a light-fortnight is considered 'close' and a million years is considered 'soon'.
(Score: 0) by Anonymous Coward on Sunday September 03 2017, @05:53AM
If we survive the next 1.3 million years, I can't see why we'd need a generation ship to travel a fraction of a light year. If we decided to build a nuclear pulse propulsion ship for such a trip today, we could develop the tech within a couple decades, and the trip itself would only take a few years (25 years at 1% of c; speeds up to 10% of c are considered practical). Surely 1.3-million-year-future us can do at least that well, whether by pulsed nuclear propulsion or some other means.