Compared to other stars, the Sun is rather modest, belongs to a class of so-called yellow dwarf.The temperature of the surface of about 6000oS.Such stars (spectral type G) live about 9-10 billion years, until hydrogen contained in them is converted into helium.When stocks run out of hydrogen, comes the last stage of their lives.The star begins to rapidly cool the temperature of the surface drops to about 3000oS, which corresponds to the red stars belonging to the spectral class M. Simultaneously, its dimensions are increased dramatically.Star as it swells, becoming much more, sometimes several hundred times.

Astronomers know of many stars, which is classified as a red giant.For example, the star Betelgeuse in the constellation Orion beautiful diameter is almost 500 times greater than our Sun!About the
same size at the red giant named Antares - the brightest star in the constellation Scorpius.If there had been a sudden some of the stars in the place of the sun, life on earth would cease immediately.As their external border would pass beyond the orbit of our planet.

Alas, that such a fate is likely and expects Earth.After all, astronomical observations and physical-mathematical calculations show that with very high probability our Sun end their way of life will become a red giant.And it does not matter whether it will swallow the Earth, or only then will be quite close to her.Even in the second case, the temperature on the surface of the Earth rises to such an extent that the biological life becomes impossible.

A comforting that such a catastrophe will happen a very long time.According to the calculations of astrophysicists sun, there are about 5 billion years.That is, it is in his prime, reaching only half of life.Before coming cataclysm will take at least another 4 billion years.So while the inhabitants of the earth can not worry.And in the distant future, when interstellar travel will be commonplace, perhaps, be able to find another planet suitable for life and have her start a new civilization on earth.