Results 1 to 25 of 25

Thread: How often do we get close passages?

  1. #1
    Join Date
    May 2004
    Posts
    1,664

    How often do we get close passages?

    Gliese 710 is now expected to miss the solar system by 13,000 AU about the year 1,352,000 AD https://en.wikipedia.org/wiki/Gliese_710
    How often does a star come this close to the sun, per billion years?
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  2. #2
    Join Date
    Jul 2005
    Location
    Massachusetts, USA
    Posts
    21,770
    I'm going to guess about once every million years.
    If you want a more precise number, tell us what the lower bound for what you'd call a star (15 Jupiter masses?), and do you mean exactly 13,000 AU as the threshold?
    Once we have those numbers, the number you ask for should be easy to calculate.
    Forming opinions as we speak

  3. #3
    Join Date
    May 2004
    Posts
    1,664
    Let's cut it at the "classical" red dwarf limit (0.08 solar masses) and have it 13,000 AU or closer.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  4. #4
    Join Date
    Apr 2005
    Posts
    2,292
    There was a list of close approaches published just a few years ago. I remember linking to it on here.

    However, the closest approaches in that article were in the light-year range, I think there is one due in about 35,000 years or so.

    I looked at the Wikipedia link where it says Gliese 710 will approach to 0.2 light years.

    But the reference given on that wiki page does not say this as far as I can see. So where has this information come from?

    It also says there is a more-than-zero probability of it approaching to 1000 AU !

    Anyhow, this GL 710 approach is much closer than in the list I referred to.

    I have also linked in the past a paper which gave estimates for close stellar encounter rates in different regions of the galaxy and in globular clusters.

    The upshot was that stellar encounters in the central few kpc of the galaxy and in globular clusters are too frequent to allow complex life to evolve in those regions.

  5. #5
    Join Date
    Apr 2005
    Posts
    2,292
    Quote Originally Posted by Tom Mazanec View Post
    Gliese 710 is now expected to miss the solar system by 13,000 AU about the year 1,352,000 AD https://en.wikipedia.org/wiki/Gliese_710
    How often does a star come this close to the sun, per billion years?
    It's about once every 1 or 2 billion years.

    t = 3.3E+07 years * (100 pc^-3/rho) * (mean relative speed of objects km/s) * (1000 AU/r) * (Msun/Mtotal)

    rho is the stellar density (0.12/pc^-3 in our locality)

    r is the encounter distance, in this case 13000 AU.

    The last term is the ratio of the sun's mass to the sum of the masses of the two stars.

    The one question I have is the mean relative speed of objects. I have assumed 10 km/s as an order of mag but others may know better.
    Last edited by kzb; 2018-Apr-13 at 12:53 PM. Reason: sums wrong

  6. #6
    Join Date
    Jul 2005
    Posts
    16,137
    Twenty years ago, based on Hipparcos data, Sanchez et al. set a lower bound of 4.2 * D2.02/Myr, where D is the distance of closest approach in parsecs. Since 13000AU = 0.063pc, that comes to 0.016/Myr = 16 per billion years. They expected more because Hip was incomplete for low mass stars.

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

  7. #7
    Join Date
    Sep 2003
    Posts
    12,235
    Quote Originally Posted by grant hutchison View Post
    Twenty years ago, based on Hipparcos data, Sanchez et al. set a lower bound of 4.2 * D2.02/Myr, where D is the distance of closest approach in parsecs. Since 13000AU = 0.063pc, that comes to 0.016/Myr = 16 per billion years. They expected more because Hip was incomplete for low mass stars.
    Nice find, Grant. [That paper shows a slightly different equation (3.5D2.12/Myr).] I assume the extrapolation to a billion years would be fairly speculative, but the best available.
    Last edited by George; 2018-Apr-13 at 03:30 PM.
    We know time flies, we just can't see its wings.

  8. #8
    Join Date
    Jul 2005
    Posts
    16,137
    Quote Originally Posted by George View Post
    [That paper shows a slightly different equation (3.5D2.12/Myr).]
    That's interesting. The preprint in my file drawer has the equation I gave. They must have responded to reviewer feedback before publication. The revision takes it down to 10 per billion.

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

  9. #9
    Join Date
    May 2004
    Posts
    1,664
    This is another star I look forward to seeing in the GAIA release coming up. See if the estimated distance gets any closer.
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  10. #10
    Join Date
    Apr 2005
    Posts
    2,292
    <deleted post>
    Last edited by kzb; 2018-Apr-16 at 10:06 AM.

  11. #11
    Join Date
    Apr 2005
    Posts
    2,292
    Whichever equation you believe, it does seem that encounters similar to this are not uncommon.

    Travel between stellar systems that are 0.2 light years apart is less difficult than systems 5 light years apart.

    As I've said before on here, this is an argument against that proposed solution to the Fermi paradox, that interstellar travel is just too difficult.

  12. #12
    Join Date
    Feb 2006
    Posts
    410
    FWIW, "Scholz’s star" (WISE J072003.20-084651.2) probably came within 52,000 AU about 70,000 years ago.
    See http://www.rochester.edu/newscenter/scholz-star/ and

    The Closest Known Flyby of a Star to the Solar System
    Eric E. Mamajek, et al.
    https://arxiv.org/abs/1502.04655

    That paper estimates passages within 0.25 pc happen at a rate of about 0.1/Myr.
    Selden

  13. #13
    Join Date
    Sep 2003
    Posts
    12,235
    Quote Originally Posted by selden View Post
    The Closest Known Flyby of a Star to the Solar System
    Eric E. Mamajek, et al.
    https://arxiv.org/abs/1502.04655

    That paper estimates passages within 0.25 pc happen at a rate of about 0.1/Myr.
    I think that estimate comes from the same folks (Garcia-Sanchez et al) Grant references, but in an updated 2001 paper. [I failed to snag it.]
    We know time flies, we just can't see its wings.

  14. #14
    Join Date
    Feb 2006
    Posts
    410
    Quote Originally Posted by George View Post
    I think that estimate comes from the same folks (Garcia-Sanchez et al) Grant references, but in an updated 2001 paper. [I failed to snag it.]
    You're right. Sorry for my sloppy attribution.
    Selden

  15. #15
    Join Date
    Sep 2003
    Posts
    12,235
    Quote Originally Posted by selden View Post
    You're right. Sorry for my sloppy attribution.
    Just a nit.

    But it's interesting that there seems to be a significant change in their earlier equation. I'm not that great at finding articles and I had no luck in my novice attempt to find this newer one. Perhaps someone will find this 2001 paper so we can update the equation.
    We know time flies, we just can't see its wings.

  16. #16
    Join Date
    Feb 2006
    Posts
    410
    The full text of the published paper is behind The American Astronomical Society's paywall, which probably is why you couldn't find it by a Web search.

    If you have access to a library which subscribes to the journal, you should be able to get it for free from them.

    STELLAR ENCOUNTERS WITH THE OORT CLOUD BASED ON HIPPARCOS DATA
    JOAN GARCIŤA-SAŤNCHEZ, et.al.

    (c) 1999. The American Astronomical Society. All rights reserved. Printed in U.S.A.
    Received 1998 May 15 ; accepted 1998 September 4

    However, its abstract is available for free at http://adsabs.harvard.edu/abs/1999AJ....117.1042G and says
    We find that the rate of close approaches by star systems (single or multiple stars) within a distance D (in parsecs) from the Sun is given by N = 3.5D2.12 Myr-1, less than the number predicted by a simple stellar dynamics model.
    I also found a couple of copies of the preprint. This one has handwritten figure numbers, so it's probably the oldest: http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

    They say
    We find that the rate of close approaches by star systems (single or multiple stars) within a distance D (in parsecs) from t h e Sun is given by N = 4.2 D2.02M yr-1, less than the numbers predicted by simple stellar dynamics models.
    Note that "numbers" and "models" were changed, too, from plural to singular.
    Last edited by selden; 2018-Apr-19 at 08:57 PM.
    Selden

  17. #17
    Join Date
    May 2004
    Posts
    1,664
    When will I find out the refined estimate from GAIA DR2? How long does it take for such data to result in a published prediction?
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  18. #18
    Join Date
    Feb 2006
    Posts
    410
    That's entirely up to whoever is interested in doing the research and whatever other priorities they might have. You could try contacting one of the authors of the papers and ask about it.
    Selden

  19. #19
    Join Date
    May 2004
    Posts
    1,664
    Quote Originally Posted by selden View Post
    That's entirely up to whoever is interested in doing the research and whatever other priorities they might have. You could try contacting one of the authors of the papers and ask about it.
    How would I go about doing that? Should I try to find their email or phone number? And how would I find that information?
    What is the best way of doing this?
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  20. #20
    Join Date
    Feb 2006
    Posts
    410
    All published scientific articles include the names and institutional affiliations of their authors.

    The Web sites of most research and educational institutions include directories of everyone affiliated with them.

    Another location method is to do a generic Web search specifying the author's name and the name of the institution.
    Last edited by selden; 2018-Apr-28 at 01:07 PM.
    Selden

  21. #21
    Join Date
    Jun 2005
    Posts
    12,763
    And just to add, published papers will have at least one ‘corresponding author’ listed, with the email and address.


    Sent from my iPhone using Tapatalk
    As above, so below

  22. #22
    Join Date
    Feb 2006
    Posts
    410
    https://arxiv.org/pdf/1805.02644


    An independent confirmation of the future flyby of Gliese 710 to the solar system using Gaia DR2

    Authors: R. de la Fuente Marcos, C. de la Fuente Marcos

    7-May-2018
    Selden

  23. #23
    Join Date
    Apr 2005
    Posts
    2,292
    Quote Originally Posted by selden View Post
    https://arxiv.org/pdf/1805.02644


    An independent confirmation of the future flyby of Gliese 710 to the solar system using Gaia DR2

    Authors: R. de la Fuente Marcos, C. de la Fuente Marcos

    7-May-2018

    Thanks for posting that!

    This paper finds the Gliese 710 approach will be even closer than the 13,000AU in the previous article. The central expectation is 10,721 +/- 2114 AU.

    There is a small chance it could be as close as 4303 AU.

  24. #24
    Join Date
    May 2004
    Posts
    1,664
    Will future data Releases refine this further?
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  25. #25
    Join Date
    Feb 2006
    Posts
    410
    Yes: future Gaia data releases are intended to have better accuracy in their measurements. Unfortunately, though, the next one (DR3) won't be published for another two years.
    Selden

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •