Question: why is the sun so hot

Alexander Allen answered on 11 Mar 2019:

Short answer: The sun is so hot because it is a long, drawn-out, continuous nuclear explosion…

Longer answer: The sun is big… and despite this it’s made up primarily of the lightest atoms in the universe. These atoms have condensed together and eventually cause a gravitational field; there is a LOT of hydrogen. This in turn attracts even more hydrogen and the pressure due to all of that hydrogen being there causes the atoms to heat up.

On heating up the atoms are stripped apart with its particles making a big soup of positive and negative charges, called plasma. The pressures get so intense that the atoms are forced together and they like this! If you can get hydrogen atoms close enough together they fuse into a big atom: helium. The process of fusing (although it needs a lot of energy to start) releases energy in such big amounts. The temperature skyrockets up to 15 million degrees in the centre and this allows a chain reaction of all of that hydrogen being forced together and releasing more and more energy… It’s an explosion and it will continue as long as there is hydrogen to fuse… after that it has to get much hotter to fuse the bigger atoms and this is part of the death of a star… but that is billions of years away!