Question 1

Why doesn't the sun combust all at once instead of bits at a time? when you light a plume of gas, or pool of gasoline, it flashes and burns all at once.  Why doesn't the sun do the same?  Does it have to do with the fact that it's not a gas, but a plasma, or maybe the absence of oxygen?  To be clear, I'm not asking why it doesn't explode apart from the energy of the fusion reaction taking place there, I'm aware that is balanced by the massive gravity of the sun, but rather why is it hanging around long enough to get to the point of fusion in the first place.  What prevented the entire thing from combusting all at once as soon as temperatures go high enough to ignite the gases?  I think it has to do with the presence of O2, and ratios needed for combustion.  Either there isn't enough O2 for combustion to take place or the ratios are not correct for combustion, but it could be something else all together.   Thanks, T.S.

Accepted Answer

There is no "combustion" happening in the sun.   The heat & light are by products of fusion.

Question 2

Why does it take so long (100k years) for photons to reach the surface of the sun? What have they been doing below the surface for all that time?

Accepted Answer

The photons don't fly out in a straight path.  They bounce along.  They hit an atom, are absorbed and remitted all along the path from birth to moment they escape the sun.  So you can imagine the photon as a pinball, bouncing its way, randomly out of the radiative zone.  That immense size of the zone (relative to the photon) and the density of atoms is why the process takes so long.

Question 3

see we all know that FUSION REACTION takes place in the sun .. now in fusion reaction the atoms combine to form heavy molecules correct? then why isn't the sun expanding? 
if any body knows pls ans above quest

Accepted Answer

Because the rate of fusion is constant, putting out the same amount of outward energy. It won't expand until the core gets hot enough to start fusing helium into larger elements, increasing the released energy. Then the sun will turn into a red giant.

https://www.khanacademy.org/science/cosmology-and-astronomy/stellar-life-topic/stellar-life-death-tutorial/v/becoming-a-red-giant

https://www.khanacademy.org/science/cosmology-and-astronomy/stellar-life-topic/stellar-life-death-tutorial/v/becoming-a-red-giant

Question 4

You know there is a point when the sun goes out. What will happen to the planets because they are pulled in orbit by the sun's gravitational pull? Will they scatter around space? What will happen?

Accepted Answer

The mass of the Sun will be largely unchanged. The planets that weren't destroyed during the red giant phase will likely still be around, maybe migrated outward a bit more due to the sun casting off some of its mass in its end stages.

Question 5

Hypothetically speaking, if the sun were to lose it's gravity and combust- how many planets would it wipe out? It's powerful enough to wipe out Earth? What about the rest of the solar system though?

Accepted Answer

Well, technically the sun couldn't combust, because combustion is the process of burning, the sun is undergoing fusion. It is hard to say accurately, but likely the sun will explode in another 4 billion years, which would completely wipe out the inner planets. The outer planets may survive, but the intense ejections of energy from the explosion would have devastating effects on them.

Course: NOVA Labs > Unit 1

The Sun's energy

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