Star system

In addition to individual stars, binary star system can be two or more stars gravitationally bound in orbit around each other , the most common binary star system is a binary star , but three or more star systems have been found . And because the reason you want a stable orbit , these binary star systems often form the Star class rail system . There are also larger , known as cluster group : ranging from only a few stellar co- stars , the most massive with hundreds of thousands of stars , called globular clusters in the group .
Star system is a long time in the gravitational field under the constraint of a particular group of stars , often by huge O and B stars form , and 80% of stars are binary star system is a multiple star system . But some stars because of the smaller individual stellar objects were found and increased only 25 percent were found to have red dwarf companion . Because 85% of the stars are red dwarfs , so the majority of stars in the Milky Way are separate .
Distribution of stars in the universe is not uniform , and usually with the interstellar gas , dust in galaxies together . A typical galaxy has hundreds of billions of stars , and then the number of galaxies in the observable universe is also more than one hundred billion ( 1011 ) . I believe that the past exists only in galaxies of stars , but in intergalactic space has also been found in stars. Astronomers estimate there are at least 700 universe Gai (7 × 1022) stars.
In addition to the Sun, the Earth 's closest star is Proxima Centauri star distance is 39.9 trillion ( 1012 ) kilometers , or 4.2 light-years. Light from Proxima Centauri star to 4.2 years to reach Earth . On the space shuttle orbiting the Earth orbit speed of about 8 km / sec ( about 30,000 kilometers per hour ), you need 150,000 years to arrive there. Like distance , including the neighboring regions of the solar system , the galaxy disk is typical . In the center of the galaxy and globular clusters , the distance will be much closer to the star , and the distance of the halo stars are more distant .
Since relative to the center , from the galaxy of stars is very open , so the stars collide with each other is very rare. But in the center of globular clusters or galaxies , stellar collisions are very common . Such collisions will form blue stragglers , these abnormal clusters of stars than in the same sequence with the same stellar luminosity of the main has a higher surface temperature.
The distance between the very distant stars , astronomy general use light years to measure the distance between stars . The determination of the distance can be measured by annual parallax method , cluster parallax method , mechanical parallax method , Cepheid method.