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About Stars: Young Stars

Stars form in groups of a few up to many thousands. This happens when one of the numerous interstellar nebulae begins to collapse (interstellar = between the stars). It gets denser and denser and breaks up into segments, so called Bok globules. These are the progenitors of the protostars, which can still have a size of some light-years.

The protostars densify more and more because of their own gravitation and begin to shine due to the released gravitational energy. Meanwhile the cloud of the protostar still can break up, depending on its angular momentum, in multiple systems and dust disks, the progenitor of planets. The early days of stars are very turbulent and the star can erupt from time to time.

When finally pressure and temperature in the center of the cloud excess a certain value the star begins its nuclear fusion. First all available deuterium is fusioned into helium 3. Is this done the star shrinks for a last time until the real hydrogen fusion can start. From there on the star is stable and has reached the main sequence, its up to 100 000 years lasting youth is over.

Example: T Tauri

Back: About Stars | Continue: Main Sequence Stars
Stellar birth in the Eagle Nebula (M16), several Bok globules are visible.
Photo: Nasa

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