I was wondering what would happen in the sun if fusion reactions suddenly shut off?

Answer 1

We would all die.

Answer 2

OK, first, that simply could not happen due to the overall mass density of the free Hydrogen that makes up 99.5 percent of the suns bulk, but, hypothetical, if it did, the ongoing act of hydrogen fusion creates an outward pressure that is counter balanced by the gravitational effect of the mass, if the fusion process stopped the gravitational pull would kick in and the sun would shrink until the density of the mass grew great enough to restart the fusion process, at witch point the outer non fusing mass on the surface would suddenly blow off creating a supernova like effect, this is essentially what happens when a star runs out of hydrogen to fuse, it takes a slightly greater density and temperature to start the fusion process in helium, then. when the star sequences thru the helium fusion cycle, it happens again in a true supernova when the mass has collapsed enough to kick off the fusion process in the noble gasses , argon,krypton,neon, and freon, once those are burned out you get a final nova and what is left is called a white dwarf, the other possibility is if a star is at least 4 times ( approx ) the size of our sun, when the hydrogen/helium fusion process ends the mass collapses past the Nobel gas kick off to fast and you end up with a runaway implosion that could end at the neutron star stage, but is more likely to form a new black hole

Answer 3

Scientists expect this, eventually.

Fusion exerts energy upon the atoms that comprise it. This "pushes" most of the sun's mass outward like a balloon, yet gravity holds that mass central to the suns core. There is a balace between the push of fusion, and gravity.

Without fusion energy, the gravity would gather all material that our sun has towards its center. This would actually create ANOTHER FUSION REACTOR that would push the sun's size much larger. Once this second reactor "burned itself out", a second collapse will occur. Our sun will then explode; not all do.

Answer 4

There are some good answers here, but there is one problem - the sun is not sufficiently large (massive) enough to go nova or supernova.

As it is sequencing, it will become a red giant expanding slightly larger than the earth's orbit. Then it will contract while shedding any residual energy to a burnt cinder approximately the size of the earth.

Answer 5

In about 4.5-billion years exactly that will happen. At that time, the sun will become a white dwarf star, with a diameter not much larger than Earth. If this happened today, all life on Earth would end.

Answer 6

We would all be dead just over 8 minutes after this happened as that is how long it takes the sun's electromagnetic energy to reach Earth travelling at the speed of light. It would get so cold so fast you would instantaneously freeze and you would not even know it.

Answer 7

I'd rather not think about it...

Answer 8

It would not be good.