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posted by Fnord666 on Sunday September 03 2017, @12:22AM   Printer-friendly
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'.


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  • (Score: 2) by mhajicek on Sunday September 03 2017, @05:03AM (3 children)

    by mhajicek (51) on Sunday September 03 2017, @05:03AM (#563072)

    Now our civilization just has to survive 1.3 million years and build a generation ship.

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  • (Score: 4, Interesting) by takyon on Sunday September 03 2017, @05:35AM (1 child)

    by takyon (881) <reversethis-{gro ... s} {ta} {noykat}> on Sunday September 03 2017, @05:35AM (#563079) Journal

    There's no guarantee that it will cause damage to human civilization.

    0.6 solar masses at as close as 0.1 light years.

    https://en.wikipedia.org/wiki/List_of_nearest_stars_and_brown_dwarfs#Future_and_past [wikipedia.org]

    (the list of past and future events could grow as more data like Gaia's comes in)

    These approaches have happened before and they didn't obliterate Earth or remove Earth from its original solar system (as far as we can tell).

    If we don't have tight control over the solar system by that time, then we deserve to get wiped out. Maybe we undergo an apocalypse and the surviving civilization is technologically crap. But if that doesn't happen, 1+ million years is plenty of time to spread to all rocks in the solar system, Alpha/Proxima Centauri, and the other stars that are approaching much sooner like Barnard's Star [wikipedia.org], Gliese 445 [wikipedia.org], and HIP 85605 [wikipedia.org]. When Gliese 710 approaches, that will be a great time to travel there as well. Meanwhile, computing will have gone through every forthcoming era [wikipedia.org] to arrive at some [kurzweilai.net] final level of performance. Combined with much better telescopes, that means more accurate and precise celestial mechanics. Combine that with much better space technology, and we can deflect any comets or other space junk that would impact Earth, Mars, et al. If something unavoidable like Planet Nine is sent on a collision course with Earth (Nibiru!), evacuate to one of the many other colonies in the solar system.

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    • (Score: 0) by Anonymous Coward on Sunday September 03 2017, @05:52AM

      by Anonymous Coward on Sunday September 03 2017, @05:52AM (#563080)

      Combine that with much better space technology, and we can deflect any comets or other space junk that would impact Earth, Mars, et al. If something unavoidable like Planet Nine is sent on a collision course with Earth (Nibiru!), evacuate to one of the many other colonies in the solar system.

      MAGAAA!

      Sorry about that, a gratuitous exercise in cynicism, a knee-jerk reaction** to putting unfounded hopes in human's nature: it strikingly resembles Trump's supporters.

      (grin)

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      ** not intended as a jerk-only reaction, even if it may appear so.

  • (Score: 0) by Anonymous Coward on Sunday September 03 2017, @05:53AM

    by Anonymous Coward on Sunday September 03 2017, @05:53AM (#563081)

    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.