Binary and multiple star systems are very common in our universe. About half of all stars are found in systems containing two or more stars. This web page shows the typical orbits for stars in binary, triple and quadruple star systems. These simulations show perfect star systems with stars of equal masses. Real multiple star systems are usually messier with stars of different masses at very different distances.
Shown on the left is a typical binary star system. The two stars follow elliptical orbits around a common centre-of-mass. Shown on the right is a special example of a binary star system where the stars follow perfectly circular orbits.
|A Binary Star System||A Circular Binary Star System|
Shown on the left is a typical triple star system. There are two stars orbiting each other at close range, and a third, more distant, star orbiting around the first two. Shown on the right is a very unusual type of triple star system. The three stars travel in a figure-of-eight trajectory. Computer simulations have shown that this type of orbit can be stable for billions of years. Nobody has yet found a figure-of-eight triple star system (a few astronomers have tried to find one), but it is possible that somewhere in our Galaxy there are stars which follow this orbit.
|A Triple Star System||A Figure-of-Eight Star System|
Shown on the left is one type of quadruple star system. It consists of two pairs of binary stars orbiting about a common centre-of-mass. Shown on the right is another type of quadruple star system. There are two very close stars orbiting each other rapidly. They are orbited by a third star as in a triple star system. These three stars are orbited by a distant fourth star.
|A Quadruple Star System||A Quadruple Star System|