Re: How long does it take a star to form?

For a human being, a star takes a long time to form. For an average star, like our own Sun, the process takes millions of years. But compared to the lifetime of a star like the Sun, 10 billion years, that's not very long at all. So astronomers tend to think of star formation as a pretty "fast" process. Since human civilization has only been around for 10,000 years or so, we can't actually follow the process of star birth by just watching an example. Astronmers are forced to look at many stars at different stages of formation and try to figure out what is going on. There are some stages of the formation process that do occur rapidly enough for us to watch and see, however. Some very young stars called T-Tauri stars can change how they emit light in less than a year. These young stars have already pretty much completely formed -- what we are seeing is the baby star clearing out the remains of the dusty gas cloud from which it was born.

There are some wonderful pictures of a stellar "nursery" at http://oposite.stsci.edu/pubinfo/pr/95/44.html