|Manu||Date: Tuesday, 17-March-2020, 6:38 PM | Message # 1|
|How common are Tatooine worlds?|
By Paul Sutter
Luke Skywalker's home planet is not so sci-fi after all.
Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of "Your Place in the Universe." Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.
We all know that iconic scene: Luke Skywalker staring forlornly — and perhaps wistfully — at the double sunset of his home planet, Tatooine.
Long a staple of science fiction, the possibility of habitable planets orbiting a pair of stars has been a challenge to solve for astronomers. But a recent analysis has shown that double sunsets may be just as common in our galaxy as the solitary kind that we know on Earth, and this has big implications for our search for life outside the solar system.
A good fraction of the stars in our galaxy are in binary pairs (or part of even larger collectives). Upwards of two-thirds of the most massive stars live with a companion, while at the other end of the mass spectrum, only one-third of the small red dwarfs find themselves in a pair. But when it comes to finding life beyond Earth, we’re most interested in sunlike stars, and for them it’s split 50/50, with half flying solo and the other half making friends.
So if half the sunlike stars in the galaxy are in pairs, could those systems host Earth-like planets?
For some time, it was thought that the complicated gravitational dynamics of multiple stars would prevent the formation of planets in the first place. But we now know there are two ways for a planet to find a stable home with multiple stellar parents. In the first case, if the binary stars are far enough apart, then a planet can orbit one of them safely, without any gravitational disturbance from its star’s sibling. In this case, the other star is so far away it would appear as just a peculiarly bright star in the planet’s night sky.
The other allowable scenario is if two stars orbit extremely close together. If you place a planet in orbit around the pair at a far enough distance, then all the planet (gravitationally speaking) sees is a single, larger star, and is able to orbit in peace.
While we have found exoplanets in both of these configurations, it was previously thought that these setups were rare and special, and we therefore shouldn’t bother directing our ET searches at binary stars, instead focusing on more promising, more likely homes for life.
Read more/source - https://www.space.com/how-common-are-tatooine-alien-planets.html