• Question: what is a star and why do we have them in space and is it true there are about a million lightyears old

    Asked by jennifer9623 to Alastair, Emma, Hywel, Keith, Vicki on 16 Jun 2010 in Categories: .
    • Photo: Alastair Sloan

      Alastair Sloan answered on 16 Jun 2010:

      A star is a massive ball of superheated plasma held together by gravity. It shines due to a process called thermonuclear fusion which releases energy that radiates into space. We have them in space because they form from molecular clouds (hydrogen and helium in space) which are found in certain areas of space. And yes, some stars could be a million light years old. The oldest start is nearly 14 billion years old and dates back to the big bang and formation of the universe.

    • Photo: Keith Brain

      Keith Brain answered on 16 Jun 2010:

      Stare are lumps of matter that are so big that they squash themselves so tightly (because of gravity) that they set of a nuclear reaction! This causes them to light up, and radiate heat (along with all sorts of other rays and particles). Our sun is also a star, but just looks different because we’re so close to it. Its actually a rather puny, uninteresting star.

      A light year is a measurement of distance, rather than of time, so they are not “light years” old. The current age of the universe is estimated to be about 14 billion years, so all stars have to be younger than this. My understanding is that most of them are just a few billion years old (our own sun is about 4.5 billion years old).

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