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Q & A: death of sun

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Hi, I want to know if the sun is a star then when it blows up will there be light on earth?
- stewart maclean (age 10)
parkdale, sherwood,canada
After the sun burns out, there will be very little light around here.

Here's a quick summary of the expected future of the sun:

From the pattern followed by other stars, astronomers expect that the sun will get slowly brighter. About four billion years from now, the sun is expected to be about 40% brighter than it is today, leading to a runaway greenhouse effect, making the planet Earth quite a lot like Venus (really hot). If the sun is like most other stars its size, it will run out of hydrogen, start burning helium, and turn into a "red giant" with an expected maximum radius possibly engulfing the orbits of Venus and the Earth at a time of about 8 billion years from now. Even if the "surface" of the sun doesn’t make it all the way out to the Earth’s orbit, all the gases emitted from the sun during the red giant phase will be enough to slow down the Earth in its orbit due to friction with the gas, causing the Earth to fall into the sun. If the sun loses enough mass early enough, then the Earth’s orbit will get larger and the Earth may escape falling in, but still it will be severely baked (or even vaporized).

After the red giant phase, the sun will eject material and shrink down to a white dwarf. There will be some light left on Earth (if there is one left after all this) from the white dwarf, but not very much.

Mike W. and Tom J.

(republished on 07/19/06)

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