4 stars within 6 AU

The universe keeps throwing neat stuff up for our telescopes to look at. A team lead by Shkolnik et al. / Univ. of HawaiiEvgenya Shkolnik (University of Hawaii), has observed a tight system of 4 stars crammed within 6 AU of one another – If located in our solar system, all four stars would fit within the orbit of Jupiter! The system consists of 2 tight binaries, with the two binary systems orbiting the center of mass for all 4 stars. There is less than a 1 in 2000 percent chance that stars of this type could form in this 4-star type of a system, and this is the first time a system like this has been found.


The two sets of binaries are very tight. One pair orbits a point between the two stars (their center of mass) with a separation of 0.06 AU, and the other set has a maximum separation of 0.56 AU. For perspective, Callista orbits Jupiter at a distance of 0.01 AU and Mercury orbits the Sun at a distance of 0.46 AU.

This is a system that is neat to model. While brown dwarfs live a long long long long time, as these stars (someday many 10s of billions of years in the future) evolve, the orbits in the system will change, material may exchange between stars, and who knows what else. This is a discovery announcement, and I can’t wait to see what the theorists do with their knowledge that these things can form!


  1. Freiddie January 10, 2008 at 9:07 pm #

    That’s very close.

  2. Richard B. Drumm January 11, 2008 at 10:39 am #

    I have to wonder about the accretion disk these stars formed from…
    -THAT- would have been a crowded house to be sure!
    Would love to know if there are any planets there…

  3. Beth January 11, 2008 at 11:18 am #

    This system sounds like it could be similar to the one in Asimov’s Nightfall. It had six stars. You mentioned that book in the globular cluster podcast. Great book. There’s the original story and then longer book with Silverberg. The Wikipedia entry (http://en.wikipedia.org/wiki/Nightfall_%28Asimov_short_story%29) summarizes the astronomy.

    Could there be planets in such a system? Could they orbit the whole bunch of stars? Could they have stable orbits around a pair? There seem to be so many intriguing questions here.

    Also, the female scientist in me is pleased to see so many female researchers presenting.

  4. Steve J January 11, 2008 at 11:32 am #

    @Beth, I was about to say that they’re not just close, four stars within the orbit of Jupiter is epic Sci Fi close. It’s very cool when you find something in nature that would seem like a nice, but frankly slightly implausible, idea if you read it in a work of fiction.

    From my strictly amateur standpoint, the formation of planets under such conditions seems even less likely, but given the nature of the whole system, as Terry Pratchett might say, reality seems to be stretched a bit thin there. Why not planets?

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