RE: A planet with four suns
October 18, 2012 at 3:50 pm
(This post was last modified: October 18, 2012 at 3:57 pm by Anomalocaris.)
(October 18, 2012 at 3:36 pm)Welsh cake Wrote: *looks around*
Goodness, we're having a lot of interesting discoveries in astronomy lately aren't we? Talk about an influx. ^^
Quote:Astronomers have found a planet whose skies are illuminated by four different suns - the first known of its type.
http://www.bbc.co.uk/news/science-environment-19950923
You wouldn't ordinarily think the celestial body could stabilise an orbit with four suns pulling on it at once... but our cosmos is anything but ordinary...
Not really, there can be many stable configurations for planets with 4 suns.
For example, if the 4 suns orbit each other very closely, and the planets are very far away in an extended orbit, then the planets would be stable because the 4 suns would be essentially equivalent to a single point mass in the middle.
Or the 4 suns are relative far apart, but the planets are very close to one of them. In the case the planets could be stable because the gravitational influence of one primary star totally dominate the planets, the other stars just excert faint perturbations like Jupiter perturb the orbit of earth around the sun.
Or there could be a combination. The 4 stars could in the the configuration of two muturally bond pairs of binary stars. In this case the planet could orbit in a medium sized orbit about one pair of close binary stars, because in relation to the size of the planet's orbit the distance between the binary stars are small, so the binary star forms approximately a single point mass for the planet. The other pair of binary star in orbit around the first pair would be very far away compare to the size of the planetary orbit, so they would form just a distant faint perturber for the stable planetary orbit.
There could also be some more goofy orbits where the planet actually transfers between two or more of the stars. Or planets could orbit one star or pair of stars but be in a stable resonance orbit in relation to another star or the other pair of stars.
The thing is there are as yet no analytical solution to the orbital mechanics involving multiple bodies of individually substantial mass. So it's not easy to analytically derive how many stable configuration there might be in an arbitrary system. But computational solutions (ie trial and error using computers to actually simulate the system rather than obtain close form mathematical solutions) show there can many unexpected stable configurations for planets in multibody systems.
