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Comment by ramchip | Hacker News Reader

[The sun] is hot because its enormous weight – about a billion billion billion tons – creates vast gravity, putting its core under colossal pressure.

But, isn't it hot because the confinement permits nuclear fusion? Just sitting there and having gravity is totally related to being hot or not; it's not like you can create energy out of nothing. If the sun were made of bananas, wouldn't it just become a very compact, cold sphere of crushed bananas?

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Banana's, if I'm not mistaken consist mostly of carbon and hydrogen. Since hydrogen is the easiest to fuse you'd get a hydrogen fusion reaction in the core of the bananasun. Over time heavier elements are created as the product of fusion.

The only thing that remains of the original bananas is the color yellow, which explains the color of the sun.

By mass, mostly oxygen and carbon (googling around, ~70+% water, ~20+% carbohydrates). Compared to the sun (~70+% hydrogen, almost all of the rest is helium), the amount of hydrogen is tiny . The density of the sun is substantially higher than its banana-replacement as well - 1.4 g/cm^3 vs a bit over 1 g/cm^3. It seems like you end up with a star that would fuse the limited amounts of hydrogen and resulting helium but is too small to get any further. The 'would be just as hot' thing seems like a bit of newspapery oversimplification - at solar masses (and below) bananium doesn't appear to be very good stellar fuel.

It's going to become a very dense, very hot (due to the squishing) bananasphere. Which is roughly comparable to a ball of water. The composition of the Sun would change drastically, it will contain a great deal more heavier nuclei and dramatically less hydrogen. The banana-sun will probably have to get a lot hotter and denser a lot sooner and start fusing helium (the hydrogen fusion product) and given its mass probably end up somewhere around here in terms of stellar evolution.

http://en.wikipedia.org/wiki/White_dwarf

Although it would probably be a off-white bananaish dwarf.

The huge mass causes a big gravitational pull towards the centre which in turn increases the temperature and pressure inside the core of the star. This enormous temperature and pressure starts nuclear reactions.

... which, in turn, resists the gravity (iirc?) i.e. supernovas are formed when this balance collapses and a series of fission/fusion reactions fail to stabalise the star. This helps create heavy elements, as the star explodes and some magnificent forces are unleashed, seeding the surrounding space with the necessary stuff for "further development" - later stage stars, planets, coments/asteroids and life.

I highly recommend Stardust by John Gribbin for a thorough and accessible read on the subject of stars and their evolution.

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