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Last Post 5/18/2015 9:44 AM by  Claire Raftery
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5/18/2015 6:51 AM

    Raymond D

    How can you tell how old the Sun is, and about how many years its lifetime really is? Also, whats the next nearest star in space closest to earth like our sun? thanks..

    Tags: Extrasolar planets, sun, stars, hertzprung-russell diagram, star lifecycle

    Claire Raftery

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    New Member

    5/18/2015 9:44 AM
    You know, that's a great question. It's one I didn't understand for a long time. There are lots of techniques that can be used to tell these things but the one that makes most sense to me is this. First, image that a group of aliens were able to take a glance at Earth, just for a second. They wouldn't be able to tell much about the human race if they were only to look at a single person, or even two or three people. However, if they were able to look at every person on the planet for one second, then they would be able to get an idea of the height of humans (most humans are between 1 (babies) and 7 ft), how long they live (there are not 200 year olds on the planet), skin color, gender, hobbies, jobs, living conditions etc. Even though they only looked for one second, they could sample a lot of people and get a huge amount of data. With the stars, it's very similar. Even though we've been studying stars for centuries, in terms of the lifetime of a star (billions of years), its more like only a few seconds. However, if we look at ALL the stars we can see, then we can gather as much generalizable data available, and start putting stars into categories. There is a famous diagram called the Hertzprung-Russell Diagram (–Russell_diagram) that helps to visualize what we know about stars. By placing the Sun in context with other stars, we can start to estimate how long the Sun has been around (about 5 billion years) and how long the Sun has left to live (about 5 more billion years). When you ask what the nearest star like our Sun is, that can mean lots of things. If you mean the nearest star with planets then I think it is Alpha Centauri B which is a little more than 4 light years away.
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