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Space Science

Big Dipper "Star" Actually a Sextuplet System 88

Posted by kdawson
from the toil-and-trouble dept.
Theosis sends word that an astronomer at the University of Rochester and his colleagues have made the surprise discovery that Alcor, one of the brightest stars in the Big Dipper, is actually two stars; and it is apparently gravitationally bound to the four-star Mizar system, making the whole group a sextuplet. This would make the Mizar-Alcor sextuplet the second-nearest such system known. The discovery is especially surprising because Alcor is one of the most studied stars in the sky. The Mizar-Alcor system has been involved in many "firsts" in the history of astronomy: "Benedetto Castelli, Galileo's protege and collaborator, first observed with a telescope that Mizar was not a single star in 1617, and Galileo observed it a week after hearing about this from Castelli, and noted it in his notebooks... Those two stars, called Mizar A and Mizar B, together with Alcor, in 1857 became the first binary stars ever photographed through a telescope. In 1890, Mizar A was discovered to itself be a binary, being the first binary to be discovered using spectroscopy. In 1908, spectroscopy revealed that Mizar B was also a pair of stars, making the group the first-known quintuple star system."
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Big Dipper "Star" Actually a Sextuplet System

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  • by JoshuaZ (1134087) on Friday December 11, 2009 @01:54PM (#30404430) Homepage
    The surprising thing is that this is only about 80 light years away. That's practically our next door neighbor. The fact that there would be undiscovered stars that close is nothing short of amazing. The new star is very small and dim which helps explain why it was not previously discovered. Still this is a good example of how much we have left to learn. We don't even have a good understanding of our nearby stellar neighbors.
    • Re: (Score:2, Interesting)

      by Anonymous Coward

      And being stars, even dim, they're easily some of the most visible objects in the sky. Consider just the Solar system and how many things in it that we don't know about. There's probably more we don't know about just within the heliopause than there is that we do know about.

    • by mcgrew (92797) * on Friday December 11, 2009 @02:46PM (#30405172) Homepage Journal

      The surprising thing is that this is only about 80 light years away. That's practically our next door neighbor.

      And if that star has a planet that had a species that had a SETI fifty years ago, they would have to keep searching for another twenty to forty years to pick up evidence of Earth having an intelligent species. They'd be waiting until 2119 before they heard the first human voice.

      I'm curious, does anyone know how many stars there are within a hundred light year radius of the sun? My googlefu is weak today...

      • Re: (Score:2, Funny)

        And if that star has a planet that had a species that had a SETI fifty years ago, they would have to keep searching for another twenty to forty years to pick up evidence of Earth having an intelligent species. They'd be waiting until 2119 before they heard the first human voice.

        And in 2200 the 2000kg tungsten slugs traveling at .9c begin crashing into the earth

        • by MadnessASAP (1052274) <madnessasap@gmail.com> on Friday December 11, 2009 @03:46PM (#30405938)

          at .9c I'm pretty sure they would be crashing through the earth. Not that it would matter, at least not for very long.

          • by rahvin112 (446269)

            Funny comment, but I seriously doubt a 2k slug going .9c could even breach the crust and hit the mantle. The crust is ~50 miles thick. People can't grasp just how big the earth is. Sure at .9c it would likely kill everything within a few thousand miles except for the bacteria and send the earth into a very long ice age, but it's not going to penetrate the core or go through the planet. If something were physically large enough and moving fast enough to penetrate the planet it's not going to punch a hole thr

            • by khayman80 (824400)
              You're right- normal objects couldn't penetrate the Earth significantly without completely destroying it. Degenerate matter could, though. For instance, a strangelet (if they exist and are stable) would probably go straight through the Earth for the same reason that bullets fly through air: the density contrast is enormous. Same with primordial mini black holes and non-interacting particles like neutrinos and (probably) dark matter.
            • by Kjella (173770)

              But the sheer force of speed is also beyond people's grasp. At 0.9c it doesn't matter what it is, it's got kinetic energy enough to be more than a bomb even if it's full of feathers. A quick search indicates the formula is E_k = mc^2( 1/(v/c)^2 -1 ) that for a 2000 kg projectile at 0.9c would be 7.7*10^20 joules or 183 gigatons. And it's not spherical, 99% of the force will be in the direction of the impact like a shaped detonation. I'd rather not check what that'll do.

          • "Through" is just another way of saying "into and then out of." And I doubt anyone would be around for the second part, so "into the earth" works for me. =)

      • by Tuoqui (1091447)

        I'm still trying to find intelligent life on Earth, if these Aliens can find some I'd appreciate them contacting me.

        • Re: (Score:2, Insightful)

          by mcgrew (92797) *

          Intelligence is relative. A housecat is incredibly intelligent, compared to an omeba. We are incredibly intelligent compared to the species we evolved from. Compare us to whatever we become in another five million years and you're right, there is no intelligent life on earth.

          OT - your sig:
          How about +5 troll? [slashdot.org]

      • by lousyd (459028)
        googlefu... Wolfram Alpha?
    • by suso (153703) *

      I think what happens is that people get interested in the latest thing and we don't fill in all the gaps of knowledge in between. Its kinda like that whole
      thing with water being spun really fast. It seems like its something simple, but its just one of the gaps in knowledge that occur when people jump ahead to the
      latest thing. Its also probably why the U.S. has such large areas of nothing in between Illinois and California. Sure there are cities and such, but its not nearly as developed as say PA or OH are.

      • by Coren22 (1625475)

        "Its kinda like that whole thing with water being spun really fast"

        Huh? Do you have a link to describe what you are trying to say?

    • It may be the same reason why people go everywhere on the planet but don't even know their own home town: It's not that interesting to look at stuff that's "always been 'round" anyway. You wouldn't expect some new insight from something that has been studied for centuries, would you? It's far more likely to make that headline news discovery somewhere where nobody looked before.

  • by Painted (1343347) on Friday December 11, 2009 @01:54PM (#30404440) Homepage
    Alcor, the star in question, is the middle star on the "handle" of the dipper.
    • by wwest4 (183559)

      The handle bend isn't really a star as much as it's an asterism, of which Mizar is the prominent member... Alcor is the much dimmer (still visible) partner. Contrary to the article, it's not merely a minority opinion that Mizar and Alcor comprise a false binary... calling the whole thing a sextuple system might be a bit of an exaggeration.

    • by wjsteele (255130)
      Wait a minute... I thought Mizar was the middle star! :) (It is, afterall, the brightest of the cluster.)

      Bill
    • And in case anyone outside the US is wondering, the big dipper is Ursa Major otherwise known as the plough.
      I'm also not from the states and am at a loss as to why it's called the bigger dipper. Could anyone inform me?
      • by wjsteele (255130)
        It is because they resemble a dipping ladel. (Which is generally referred to as a "Dipper" in the US.)

        Bill
        • by wjsteele (255130)
          I wish Slashdot would allow you to edit a previous post.

          Before any Spelling Nazis get a hold of it, it is "Ladle!"

          Bill
        • Re: (Score:3, Funny)

          by mforbes (575538)
          More specifically, the Pleiades cluster is sometimes erroneously referred to as a dipper. Thus, what we Americans usually call the Little Dipper (Ursa Minor) becomes the Big Dipper, and Ursa Major the Bigger Dipper.
          • Re: (Score:1, Informative)

            by Anonymous Coward

            Not quite. Ursa Minor == Little Dipper. The pleiades (or Subaru in Japan, look at their logo), though some confuse it as the little dipper. Ursa Major != Big Dipper. The Big Dipper is a *part* of Ursa Major.

            Sorry, but I worked in a planetarium for a number of years.

      • I'm from outside the US (Canada), and we know it as the big dipper, too. Of course, the latin name Ursa Major is known to those of us here who have a particular interest in constellations. But the name "the plough" is mostly unknown here.
        • by ceoyoyo (59147)

          Technically the big dipper, or plough in most of England, is an asterism (a recognizable pattern of stars that is NOT a constellation) composed of stars that are part of the constellation Ursa Major (the big bear).

    • by klui (457783)
  • More to come (Score:2, Informative)

    by z4ns4stu (1607909)
    From TFA:

    Mamajek is continuing his efforts to find planets around nearby stars, but his attention is not completely off Alcor and Mizar. "You see how the disk of Alcor B doesn't seem perfectly round?" says Mamajek, pointing toward an image of Alcor and its new companion. "Some of us have a feeling that Alcor might actually have another surprise in store for us.

    It just goes to show you that there's always something more to learn.

  • in the year 2110, the mizar-alcor system will be discovered to actually be a septuple star system

  • by TheGreatOrangePeel (618581) on Friday December 11, 2009 @02:14PM (#30404694) Homepage
    I suggested to my wife we try the sextruplet system with my big dipper and the neighbors, but she would have none of it.
  • by Fry-kun (619632)

    That group has also recorded a rough spectrum of the star, which Mamajek says confirms his prediction that the companion is a cool and dim M-class dwarf star.

    ...so it should at least have Roddenberries

  • FTFA: "In ancient times, people with exceptional vision discovered that one of the brightest stars in the Big Dipper was, in fact, two stars so close together that most people cannot distinguish them."

    In ancient times the atmosphere was cleaner than now, and had a lot less light pollution from towns. Yet it apparently took "exceptional vision" to see Alcor and Mizar as separate stars. I must have phenomenal eyesight then to be able see them any night it isn't cloudy.

    • by Coren22 (1625475)

      I believe they were meaning that the bigger of the two you can see was found to be a binary, not that the two you see were found. So in other words, Mizar A and B in the 1700s, Alcor was discovered much earlier as it is easy to see that it is there.

      • by Chris Burke (6130)

        Naw, TFA is talking about distinguishing Alcor and Mizar as distinct stars with the naked eye. It took telescopes to resolve Mizar as the Mizar A and B system.

        Personally, I haven't been able to see Alcor/Mizar with the naked eye on a cloudless night far away from cities and I don't need glasses, so maybe the OP just has exceptional vision.

        • by ceoyoyo (59147)

          Mizar/Alcor are distinguishable even by people who do need glasses (maybe you should get your vision checked). It's been suggested that the only-the-people-with-the-sharpest-vision thing is actually referring to another, dimmer star that appears between Mizar and Alcor and WOULD require exceptional vision to see.

    • You havent reached whatever comes after middle age then. I have trouble splitting them in a city now, but cant tell whether its because of the city lights or because my eyes are shot. They look great through a 10" dobsonian in any case :-)

    • by osu-neko (2604)

      In ancient times the atmosphere was cleaner than now, and had a lot less light pollution from towns. Yet it apparently took "exceptional vision" to see Alcor and Mizar as separate stars. I must have phenomenal eyesight then to be able see them any night it isn't cloudy.

      By ancient standards, you probably do. Especially if you have it without the use of corrective lenses that weren't available in ancient times.

  • Nearest sextuplet (Score:5, Informative)

    by sidyan (110067) on Friday December 11, 2009 @03:19PM (#30405596)

    In case anyone was wondering (and since TFA doesn't mention it), the nearest sextuplet star, is, of course, Alpha Geminorum [wikipedia.org], a.k.a. Castor, the second-brightest star in the zodiac sign of Gemini [wikipedia.org], a.k.a. the Twins. It's some 50-odd lightyears away.

    Note that Beta Geminorum [wikipedia.org], a.k.a. Pollux, is actually the brightest star in Gemini (whether Johann Bayer [wikipedia.org] labelled Castor as the alpha star because it rises first in the night's sky, or because mythologically, the twins are always labelled "Castor and Pollux", is unknown). Pollux is a single star, with one confirmed exoplanet, Polydeuces [wikipedia.org] orbitting it.

  • Nightfall (Score:5, Interesting)

    by hazem (472289) on Friday December 11, 2009 @03:54PM (#30406004) Journal

    I couldn't help but think of Asimov's story, Nightfall. In it, a planet is in a 6-star system and is never dark. Interesting things happen.

    • by ceoyoyo (59147)

      It is almost never dark.

      Whoops, should have warned about that spoiler, hey?

      • by Valdrax (32670)

        Man, you couldn't blown that more than if you'd put the spoiler in the title of the book.

  • So you are telling me that this system now has 6 suns instead of 4?
    I think this calls for George Lucas to redo all the star wars movies YET AGAIN, with
    a new backdrop featuring the 6 suns, as it could very well be a cooler movie with 6 instead of 2!!!

  • Astrobooboos (Score:3, Insightful)

    by DynaSoar (714234) on Friday December 11, 2009 @05:53PM (#30407454) Journal

    Alcor is not one of the brightest stars in the Big Dipper. It is a dim double with Mizar. We usually consider the dipper to have 7 stars: 4 in the 'pot' and three in the handle. Mizar is the center of the handle. Alcor is so close to Mizar and relatively dim that it's not even considered a point in the constellation.

    Not incorrect but misleading, Castelli was the first to see it as a double 'with a telescope'. The names themselves being Arabic, should be a tip off. Would Alcor have an Arabic name if they didn't see it? They are a visual double, not requiring a telescope to see if one has good vision (as opposed to an optical double, being line of sight but not necessarily naked eye). Such as noted by the Arabic chroniclers of astronomy, as well as the Native Americans who saw the bowl of the dipper as the bear, and the three stars in the handle as three bear cubs or some as three hunters (or sever, per the Mikmac) following the bear. All knew of the two stars. Sir Patrick Moore suggests the early writings refer to Mizar A and B instead, and gives good logical thinking, though I know of pre-tlescope maps of Mizar and Alcor, but not Mizar A and B,

    • by ascari (1400977)
      You got your mythology all wrong, dude. It's common knowledge that Alcor invented the Internet and then went on to discover Global Warming.
    • by ceoyoyo (59147)

      Resolving Mizar A and B (14 arcsecond separation) exceeds the theoretical resolving power of the human eye, and even with perfect vision your eye can't come close to that limit in the dark because your pupil dilates.

      Sir Patrick Moore suggests that the reference is to splitting Mizar and a dim star that appears between Mizar and Alcor.

  • How close do the stars have to be to be considered a binary (or n-ary) system? Isn't every star in the galaxy ultimately rotating around every other star in the galaxy?
    • I beg to differ with your question. Think of the solar system [wikipedia.org] comprising the sun, planets of various sizes and compositions (including several "gas planets" that are, arguably, just slightly-too-small proto-stars, and right out to the "scattered disc [wikipedia.org]" and even the Oort cloud [wikipedia.org]. So, from Mercury outwards*, there are objects that orbit the sun. Distance, like size, does not matter: It's all orbital mechanics [wikipedia.org]. (* And, yes, some objects notably comets [wikipedia.org] 'orbit' - for some of their regular orbital period - well insi
    • by osu-neko (2604)

      Isn't every star in the galaxy ultimately rotating around every other star in the galaxy?

      No. Every star in the universe is gravitationally affected by every other star in the universe, but none are known to actually revolve around all the others (and none rotate around anything but their own axis).

We warn the reader in advance that the proof presented here depends on a clever but highly unmotivated trick. -- Howard Anton, "Elementary Linear Algebra"

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