Many stars seem to come in pairs, like twins. Some stars even come in triplets or quadruplets. Even though these twin or triplets were formed at the same time, they're often very different. Sometimes a giant orange star is twinned with a mediium sized blue star. Sometimes a yellow star like our sun is matched with a white dwarf.
Twin stars dance with each other.
If one star is heavier than the other, the lighter one will orbit the heavier one. When the Cartwheel Galaxy collided with the constellation 'Sculptor' it unleashed a shock-wave which damaged the Cartwheel Galaxy, turning it for the better and makking spiral arms visible as faint spokes. A ring of billions of stars were formed from the matter hit by the shock wave which was travelling at 200,000 mph. The earth and eight other planets - Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto orbit the sun. The length of time it takes for each of them to complete its orbit depends on its distance from the sun.