|MadSci Network: Astronomy|
Evidence for star formation comes from both observations and theory.
Astronomers observe many regions with cold (< 100 K) dust and gas. Some of these regions contain massive stars, which have 8-15 times the mass of our Sun. These stars have very short lifetimes, less than 10 million years, which means they must have been formed recently. Recall that the Sun's age is about 4,600 million years.
In these dusty, gassy regions, there are also much less massive, cool objects. They emit a lot of infrared radiation, which makes them good targets for infrared telescopes. Many of these are surrounded by disks of material. The disks are what we expect theoretically in the formation of stars. Our own Solar System probably formed that way. The material in the disk later merged to form the planets.
We also can sometimes see the gas breaking up into lumps that are about as massive as the Sun. An especially good laboratory for this is the Eagle nebula. A good article on the Eagle Nebula may be found at http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/44/.
For an article on protoplanetary disks, see http://hubblesite.org/newscenter/newsdesk/archive/releases/1995/45/.
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