In what ways is the evolution of massive star similar to the evolution of the sun and in what ways is it diff?

Answer 1

Stellar evolution

All stars develop in a similar way.

The sun is an average sized star, much smaller than the really massive stars.

Stars form from spinning nebulae, through friction pressure builds up and through the increasing density of the hydrogen and helium gases within the centre of these spinning clouds, the gases are pushed gravitationally into a sphere called a protostar.

The density at each sphere's centre increases until the hydrogen atoms are really near to one another and their wavefunctions overlap, tunnelling them into heavier nuclei, like helium. This releases heat.

Stars' heat is an outward pressure, counteracting the inward pressure of the star's bulk's mass. Gravity attempts to squish the star thoroughly, the heat 'inflates' it.

Obviously the gravity sucking the star into nothing is much greater for a massive star than for a miserable little star like the sun.

Thus the heat of a massive star must be greater. The massive star's mass crushes down harder than the smaller star's mass. This keeps the density in the core of the massive star greater than the density of the core of the little starlet.

Thus the atoms are closer in the core of the big star and so their wavefunctions overlap more, more nucleosynthesis occurs and more vicious heat is released.

This counteracts the squashing and the squishing of the star's mass.

Small stars, alas, cannot do this.

So, the H atoms are closer in a larger star, so they are converted to He faster.

Unfortunately this means that the star runs out of hydrogen faster than the smaller stars, paradoxically.

One would think that a large bag of potatoes would be consumed slower than a miniscule bag!

Not so, a large sun swallows its whalesworth of H whole while a tiny star nibbles away ineffably slowly at its peanutsworth of H.

The stars, of all sizes fill up with He and lose H.

Since the nucleosynthesis is over, the heat cannot be released any more and so cannot battle the overdominationally crushingnesses of the star's obese bulk.

The star crunches down on itself, which increases the density of the core to such an extreme as to fear disobeying the Pauli exclusion principle.

To cut an extremely several million year long story short is

Small stars have their outer layers waft off, swelling the star into a red giant.

The electrons force themselves apart by the Pauli exclusion principle, with such dramaticness as to increase the sizes of stars terrifyingly. When the star is very large indeed, it may swallow a few planets its solar system.

Then the outer layers drift away leaving a lonely white dwarf behind.

Massive stars on the other hand run away with their collapse and thus Pauli exclusion effects more dramatically, cataclysmically exploding as the electron fly away from one another.

After a cracking explosion in the silence of space's vaccuum which you wouldn't hear, the core, which remains unhappily from a small star, crushes itself even further.

The core responds (maybe, this is my hypothesis) from the effect of Newton's third law of motion, so crushes futher, so much further that the Pauli exclusion cannot exist by the useless little electrons anymore (they're tiring now?), but the job of the Pauli exclusion has to be reacquainted to a different particle, the neutron. When neutrons take over, the core becomes termed a neutron star.

If it, as a white dwarf briefly earlier, was 3 times more massive than our sun, it will crush itself past the stage of neutron star to that of black hole.

Spacetime is stretched around a black hole, so time slows down. Black holes are the end of everything, but at least you'll know, having watched a massive star's demise into a black hole that is about to swallow you, that at least the end of a massive star is at least more exciting than that of a miserably sized star.

information sources

Hawking, S. W. 1988 : a Brief History of Time