Red+giant

A red giant is the second stage in the death of a star. Stars only become red giants if they have the mass of our current sun (about 199 million trillion trillion kilograms). This is not to be confused with a red supergiant (ten times mass of sun). Red giants like our sun will last for an average of 10 billion years before becoming a red giant. When it does, it will inflate upto 100 times its original size, also increasing its gravitational force. According to the Encarta Encyclopedia, it will have reached 2000 times its original luminosity. The red giant will turn into a white dwarf, the final stage of a star with the mass of the Sun, when it finally uses up all of its fuel.
 * Red Giant**

How the sun becomes a red giant in the first place is an entirely different topic. A star must keep on producing enough pressure to keep it from collapsing onto itself. The only way it can do this is to raise its own temperature. As it raises its temperature, it becomes more and more luminous. This happens even though its supply of hydrogen is steadily running out. This also raises the rate at which nuclear reactors are reacting within the sun. Eventually it cannot sustain its pressure any more because its supply of hydrogen has run out. this is when it turns into a red giant.

Three good examples at least can be listed of red giants. The best possible about-to-be-red-giant example is our Sun. It is estimated to turn into a red giant in 4.5 million years after which it will inflate and swallow Mercury, Venus and Earth. Mars and the beyond planets will be well out of the red giant's orbit. The Sun is about 1 AU (astronomical unit) away from Earth. However, it is not yet a red giant. The Aldebaran (Alpha Tauri) is an example of a red giant. It is about 60 light years away from Earth. Its surface temperature is about 3700 degrees celsius and is very bright in the night sky. A second example can be Arcturus (Alpha Bootis). It is the third brightest star in the sky and it about 43.9 light years away from Earth. The last example is Gamma Crucis (Gacrux). It is about 88 light years away from Earth and is third brightest in its constellation, Crux. A video showing a normal star growing into a red giant can be found by clicking [|here].

A red giant **could not** sustain human life because primarily, it's surface temperature would be way beyond human control. Second of all, before humans could adapt to the changes in the atmosphere, the red giant would collapse again to become a white dwarf, which has a very small diameter. The reasons **for** sustaining human life there might be because it had a huge space for the population of humans.

However, if we wanted to sustain human life on there, we would have to do it by going to another planet or star first. this is because when the star becomes a red giant it stretches beyond its normal diameter (immensely) and therefore swallows all matter around it. Another option might be going to another 'ready-made' red giant. However this might take thousands of years on the fastest rocket in the world because the nearest red giant (apart from the sun) happens to be about 40 light years away from Earth.

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