How Do Stars Form?

Quick Answer

Stars form when cold clouds of gas and dust collapse under gravity until the core becomes hot and dense enough to begin nuclear fusion.

The Full Story

Stars are born in giant molecular clouds made mostly of hydrogen. A disturbance, such as a nearby supernova shockwave, can cause dense clumps to collapse under their own gravity. As a clump shrinks, it spins faster and flattens into a disc, with a hot protostar forming at the centre. When the core reaches around 10 million degrees Celsius, hydrogen nuclei fuse into helium and the star begins to shine. Leftover material in the disc can form planets, which is how our Solar System formed about 4.6 billion years ago.

Key Facts

1.The Orion Nebula, about 1,300 light-years away, is one of the closest large star-forming regions.

2.Star formation from collapse to fusion can take a few hundred thousand to tens of millions of years, depending on mass.

3.The Milky Way forms very roughly a few new stars each year.

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