Big Dipper "Star" Actually a Sextuplet System 88
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."
In case anyone was wondering... (Score:5, Informative)
More to come (Score:2, Informative)
It just goes to show you that there's always something more to learn.
Re:Actually a quadruple... (Score:5, Informative)
Re:Only 78 light years away (Score:4, 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.
Nearest sextuplet (Score:5, Informative)
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.
Re:Only 78 light years away (Score:2, Informative)
2539 stars within 80 light years (Score:4, 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).
Re:Only 78 light years away (Score:3, Informative)
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!
Re:In case anyone was wondering... (Score:1, Informative)
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.