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Big Dipper "Star" Actually a Sextuplet System

Posted by kdawson on 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."

12 of 88 comments (clear)

  1. Only 78 light years away by JoshuaZ · · Score: 5, Interesting

    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.

    1. Re:Only 78 light years away by Urban+Garlic · · Score: 3, Informative

      Actually, that chart only says that there are about 70 stars whose distance is approximately 80 l.y. from here.

      The cumulative total is more than that.

      --
      2*3*3*3*3*11*251
    2. Re:Only 78 light years away by mcgrew · · Score: 4, Interesting

      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...

      --
      Free Martian Whores!
    3. Re:Only 78 light years away by TwineLogic · · Score: 3, Informative

      The chart has a linear regression line fit to it, and it seems like a decent fit line. So we might take the equation for the number of stars at a certain radius (let's call it stars_on_sphere(R) function) would be:

            stars_on_sphere(R) = m R + b

      From the graph it appears m = 5 / 6 and b = -1. The cumulative total suggested by the graph would then be the integral:

            stars_within_distance(R) = Integral( 5 R / 6 - 1 ) = (5/12) R^2 - R

      At 80 l.y. that is around 2600 stars within 80 light years.

      whoot, 2600!

    4. Re:Only 78 light years away by MadnessASAP · · Score: 4, Insightful

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

      --
      I may agree with what you say, but I will defend to the death your right to face the consequences of saying it.
  2. In case anyone was wondering... by Painted · · Score: 5, Informative

    Alcor, the star in question, is the middle star on the "handle" of the dipper.

    --
    http://marsandmore.com - Posters of space, spacecraft, and astronomy.
  3. Re:Actually a quadruple... by asdf7890 · · Score: 4, Informative

    You don't even need to RTFA - it is in the summary. Miza is a binary of binaries and Alcor is a binary. (2+2)+2=6. So you would not guess correctly.

  4. I suggested this... by TheGreatOrangePeel · · Score: 4, Funny

    I suggested to my wife we try the sextruplet system with my big dipper and the neighbors, but she would have none of it.

  5. Re:obvious logical deduction: by Reziac · · Score: 4, Funny

    More likely they'll be discovered to be giant glowing tribbles. How else do you explain it going from one star to six in just a few hundred years? ;)

    --
    ~REZ~ #43301. Who'd fake being me anyway?
  6. Nearest sextuplet by sidyan · · Score: 5, Informative

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

    Note that Beta Geminorum, a.k.a. Pollux, is actually the brightest star in Gemini (whether Johann Bayer 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 orbitting it.

  7. 2539 stars within 80 light years by AlpineR · · Score: 3, Informative

    Indeed. And what an odd way to draw a chart, omitting a key to what counts as "80 light years". Does it count stars 80.1 light years away? 80.5? 82? Probably (79.5,80.5], but I've never seen "at" have an uncertainty of three trillion miles.

    The source for that chart says there are 2539 stars within 80 light years (24.53 parsecs).

  8. Nightfall by hazem · · Score: 4, Interesting

    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.