home I the formation of stars I the evolution of stars I animations I references
The formation of stars takes place within large clusters of dust and gas. These low density clouds of gas in which a star is born are called nebulae (See figure 1.2, 1.3). The clouds, which are mostly composed of hydrogen, collapse in on itself, due to gravity. This slow process can be quickened by a passing star or shockwave from a supernova. As the cloud collapses, it starts to swirl. Over millions of years, more hydrogen gas is pulled in the spinning cloud. The collisions, which occur between the hydrogen atoms, start to heat the gas in the cloud. Once the temperature reaches 15, 000, 000 ºC, nuclear fusion may begin in the core.
Nuclear fusion occurs when atoms fuse to form an element with larger atoms, releasing large amounts of energy. In this case, nuclear fusion will form the heavier element, Helium. This causes the cloud to glow and form a protostar. The protostar will stop collapsing at this point because of the energy surge from fusion, which flows out of core, stopping its collapse. The protostar will continue to gain mass (which varies depending on the matter available in the nebula), until it is stabilized. At this point the protostar will become what is known as a main-sequence star, which may last millions and maybe even billions of years to come.
Figure 1.1- (above) Three examples of nebulae.
Figure 1.2 (left) A group of young stars.
Did you know... that baby stars are bigger than an adult star in the main-sequence star.
1 http://map.gsfc.nasa.gov/m_uni/uni_101stars.html
2http://www.telescope.org/rti/nuffield/research/res8.html
3http://www.imsa.edu/edu/astro/astrostudents/97_98_1/t109p2/birth.html
4 http://www.mstc.fayette.k12.ky.us/~atruszcz/starsandbebula/ life_cycle_of_a_star.htm