First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Sextup

[Nyrath]

http://www.sciencedaily.com/releases/2009/12/091210092005.htm

 

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. The two stars, Alcor and Mizar, were the first binary stars -- a pair of stars that orbit each other -- ever known.

 

Modern telescopes have since found that Mizar is itself a pair of binaries, revealing what was once thought of as a single star to be four stars orbiting each other. Alcor has been sometimes considered a fifth member of the system, orbiting far away from the Mizar quadruplet.

 

Now, an astronomer at the University of Rochester and his colleagues have made the surprise discovery that Alcor is also actually two stars, and is apparently gravitationally bound to the Mizar system, making the whole group a sextuplet.

 

So the Alcor system could contain six solar systems with habitable planets. And the inhabitants could reach the other systems with ordinary spacecraft, no star ships required.

 

Though it does seem like the Alcor binary proper is at a greater distance than the others. So the four other systems can be close knit, up until that fateful day when an exploration mission to Alcor stumbles over the xenophobic Tarantula-Crabs of Alcor 2 and their star empire.

[KawangaKid]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

So the Alcor system could contain six solar systems with habitable planets. And the inhabitants could reach the other systems with ordinary spacecraft' date=' no star ships required.[/quote']

 

What are the travel times involved? Days? Months?

[Sundog]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

Modern tech? Months in the case of the close binaries, years/decades to Mizar from Alcor. But then, with modern tech we're talking months to reach Mars.

[BobGreenwade]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

Twins becoming sextuplets?

 

This was quite an impressive bit of labor.

[ajackson]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

years/decades to Mizar from Alcor.

More than that. The separation is at least a quarter of a light year; with current tech we're talking millennia.

[Nyrath]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

More than that. The separation is at least a quarter of a light year; with current tech we're talking millennia.

 

Ah, and the first exploration ship with post-current-tech reaches Alcor in a matter of a few years, only to unleash the horror. The Tarantula-Crabs empire slaughters the exploration mission, reverse-engineers the propulsion system, and the Mizarians are blissfully unaware that the count-down to total war has begun.

 

"But doctor! These telescopic observations seem to indicate a vast array of spacecraft approaching our star systems! They might be hostile. We have to start building defenses."

 

"Bah, sthuff und nonsense you silly underling tool of der military-industrial complex! You probably botched der observation. Und anyway efferbody knows that any species that is advanced enough to make spaceships has also grown out of war mongering and udder hostile sthuff. "

 

( and when the invasion fleet arrives, the situation will look like one of the Terminator movies, except all the nasty robots will have eight legs )

[Lawnmower Boy]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

There's a vaguely similar situation in Vinge's Deepness in the Sky that is way creepier than xenophagous aliens.

[austenandrews]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

Out of curiosity, how likely is it that gravitationally-bound stars could have planets? Is it equivalent to moons circling a planet circling the sun, or are the stellar forces much greater? I'd always heard binary stars had very little chance of developing stable planetary orbits.

[Cancer]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

If the orbit sizes are very different, it's possible. In effect, if the planet is so close to its own star that exterior stars are unimportant, then a planet could survive. Planet systems are much more problematic. Alternately, if the planet is so far out that all the stars are (in effect) just a single mass, then the planet could have a stable orbit from the point of view of the star system. With a wide system like Mizar-Alcor that distance would be so large the planet would be at best very weakly bound to the system.

 

Long ago IIRC the rule of thumb was a factor of 25 for the distance ratio; that is, if your planet was no further out than 1 AU, the other star needed to get no closer than 25 AU. That's assuming a single planet. Systems of planets are probably not going to be stable in the long run no matter what.

[austenandrews]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

Doesn't sound like a lot of hope for terrestrial planets.

[novi]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

On the one hand, the current thinking is that for planets in binary star systems, the factor is actually three (i.e., 1/3 the separation, or 3 times the separation between the stars). So more room to work with.

 

The system itself? To start with, all the stars are Type A, bigger and brighter than the sun, and a life span of under a billion years, so if they have planets, they've barely had time to settle down. Steve's guess in Star HERO is that the habital zone for such a system is about 3 AU to 9 AU. Mizar A has a period of 20.5 days, which doesn't rule out planets circling both stars. Mizar B does it in 6 months, which is probably about an AU seperation, so it might also have planets around both. The seperation between each pair is at least 500 AU, so there's plenty of room between them. But this is subject to the caveat that the eccentricity of the whole system is not known. The pairs may pass close enough to scatter their planets, And who knows what Alcor is up to in its million year orbit.

[Markdoc]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

Doesn't sound like a lot of hope for terrestrial planets.

 

Unless, of course, the whole setup is artificial

 

cheers, Mark

[McCoy]

Re: First Known Binary Star Is Discovered to Be a Triplet, Quadruplet, Quintuplet, Se

 

Doesn't sound like a lot of hope for terrestrial planets.

Then again, many if not most of the planets discovered outside our solar system are in orbits that would have been considered impossible 20 years ago.