How much hydrogen does a star have?

We find out what that magic amount is to keep a star alive

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A high proportion of stars possess around 90 per cent hydrogen gas

A high proportion of stars possess around 90 per cent hydrogen gas

Asked by Ben Sulivan

Many stars are made of about 90 per cent hydrogen, with most of the remainder being helium and a very small fraction of heavier elements.

Stars form from the sudden collapse of clouds of interstellar matter and during its lifetime a star burns its hydrogen to form helium. In fact, in order for a star to form, it must be able to start the process of burning hydrogen. Whether or not a star can begin this process is dependant on the collapsing interstellar cloud’s mass.

The original conditions of the interstellar cloud can determine a star’s type, how bright it is and how long it’s likely to last. Stellar composition can vary – newer stars are found to have a relatively higher percentage of heavier elements. However, for their birth they need conditions that enable them to burn their hydrogen.

Answered by Zoe Baily at the National Space Centre

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