Quote:
Originally Posted by renormalised
Hi Mike. Also to add to what Rob has written, a red star is not necessarily old, either. Small stars...those with less than 0.5 times the mass of our Sun, are cool stars. As Rob has mentioned, these stars glow with a "red" heat and so are orange-red in colour. These stars can be as new as newborn babies. Because these stars are so small, they stay reddish in colour for all of their lives, which can be up to quite a few trillion years, for the smallest of them. These types of stars are the ordinary red stars, that like the Sun, are burning hydrogen in their cores. If the star is a large star and is red, then it can be an old star. When they're like this, they call them red giants or red supergiants. At this stage, they are red because they have gotten so huge their surface has cooled down to glow red and they have stopped burning hydrogen in their cores. They have become old stars, but even so, they may not be older than the Sun. When astronomers say a star is old, it maybe older than the Sun, but it also means that the star is getting on in age so far as the stage of life it is in. Very big stars age quickly, because they burn up their hydrogen very quickly. So they become red giants or supergiants before the smaller stars, like the Sun. Small stars can take a very long time to reach that stage in life, so they can hang around for a lot longer than the big stars.
So, you can see, when they say a star is red, it can mean many things.
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Interesting Carl, I also thought that red stars were old stars. Yesterday I was reading up on Antares, and was surprised to see that its a lot younger than the Sun. It was once a blue supergiant with 12 x the mass of our sun, and was burning its fuel at a much quicker rate. Hmmm.
The article said that the bigger the star, the harder they fall.
http://my.execpc.com/60/B3/culp/astr.../scorpius.html