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May 26, 2005
What About Twin Stars? Would They Be Suitable for Life, or Are Their Neighborhoods as Sterile as an Irradiated Fruit Fly?
When researchers pivot their radio antennas towards nearby stellar systems, in hopes of picking up the broadcasts of alien intelligence, they invariably target single stars – stars that have only planets as companions, not another star. Why the preference for single suns? It’s not some unreasonable bias toward bachelors, but merely the consequence of considering what can happen to a planet that is born to a double-star system. You may recall that Luke Skywalker once inhabited such a world, and undoubtedly had a fistful of vacation photos with double sunsets and the like. But the changing gravitational tug on planets in such systems will, over millions of years, often kick them out into the cold and unfriendly depths of space. It just didn’t seem reasonable to search for life, let alone advanced life, in such unfriendly star systems. The planets would have moved out of the neighborhood long ago.
That was then, and this is now. Theoreticians, armed with fast computers, have calculated what happens to planets in multiple-star systems. It turns out they’re not all condemned to eventual exile. There are two cases in which planets will just hang around and hang around.
1) Close-in double star systems, where the suns dance about one another in hours or days. Planets that orbit, say, a hundred million miles from this tightly pirouetting pair will experience its gravitational tug as one large star, and their orbits will remain stable for long periods of time.
2) Widely-separated doubles offer a similar opportunity. If the stars are separated by more than five times the distance at which a planet orbits one or the other of them, those planets, too, will be around for the long haul.
You might think this is all much ado about nothing. But roughly half of all stars are in multiple-star systems (doubles, mostly, but also triples and even larger litters). By including the right kind of doubles in our searches, we have doubled the amount of cosmic real estate that is worth checking out for life.
Posted by Seth Shostak on May 26, 2005 06:54 AM
Visit the Planetary Investigation Lab to see the creatures and worlds explored in the show. Go »
Comments
Keep searching. As a participant in SETI at Home I hope that the search for life will yield some results soon. We need this to counter some of the persistent superstition which still pervades our culture.
Posted by: Donald Perry on June 2, 2005 05:43 AM
Oh! I am just crazy about the *Little Twin Stars!* They are so cute!
I luv Sanrio! Little Twin Stars are way better than Hello Kitty!
I am so happy to see scientists finally taking their very special specialness seriously!
Luv, Cyndee (grade 7)
Posted by: Cyndee Keane on May 26, 2005 03:59 PM
Brilliant! I'm hooked, and I can't wait to watch Extraterrestrial on Monday.
Posted by: Amy on May 26, 2005 11:54 AM
