Star power shifts?

[Meem]

I don't know why but, I have the thought, and it goes something like this.

From my understanding, a star grows larger before it goes supernova. My question is, in the initial phase of running out of fuel and before actual collapse begins, would/does a star go through a "power-down" phase? Like a "small" contraction before the growth (red giant) and actual collapse phase?

secondary:

How long would one have to be able to observe a star or stars to even begin to consider that, or does physics offer any computational suggestions?

[Graybeard]

SUPERNOVA

The acceleration of evolution towards a time of infinitely rapid change is not so exceptional as one might at first suppose. The evolution of matter in a star follows a similar pattern.

For 99.99 percent of its existence a star burns hydrogen, fusing the atoms into helium and radiating the energy released as light. Eventually the hydrogen runs out. For a star the size of our Sun this happens after about 10 billion years -- it is currently about half way through its life. Larger stars burn up more quickly, smaller ones can last as long as a 100 billion years.

When all the hydrogen has been consumed, a star can, if it is sufficiently massive, switch to burning the helium it has created, transforming it into carbon. This keeps the star going for another million years or so. When the helium is used up the star can survive for another thousand years by fusing the carbon into neon. And when the carbon runs out the star burns the neon to form silicon. But the neon is exhausted within a year. Then, in a process that lasts only a few days, the silicon fuses into iron.

That is as far as a star can go along this particular path. Fusing iron does not release energy; it requires additional energy. The star’ s fire begins to die, and with it the energy that until now has supported the weight of its outer layers. Very quickly it begins to collapse.

As its matter becomes increasingly compressed, its gravitational field increases. Within minutes it becomes so intense that even atoms cannot withstand the pressure. Electrons are stripped away and atomic nuclei pack in upon each other, reaching densities of more than a million tons per cubic inch. This disintegration releases enormous amounts of energy, blowing off the star’ s outer layers in what is known as a “supernova.” This is one of the Universe's more spectacular shows, more energy being released during these few seconds than over the rest of the star’ s entire life.

Left behind is a neutron star -- a solid mass of neutrons a mere fifteen or so miles across. For a sufficiently massive star (one about three times the mass of the Sun) the gravitational field has now become so strong that matter itself breaks down. The star is said to have reached a singularity: a point at which the laws of physics no longer work. Mathematical equations become filled with zeros and infinities and cease to make any sense. There is a hole in space.

So intense is the gravitational field nothing can escape it. Even light is pulled back down. If no light can escape, then nothing can be seen of the star. It becomes a “black hole.”

Source Unknown

[Graybeard]

Well thanks for that Graybeard

kind regards ... Meem

[Meem]

sorry sorry!

You know, a head like mine rattles around a lot and I forget stuff! Thanks on demand!

So a short answer could be a yes? They do power shift as they change fuel sources? It's beyond me how people would even begin to calculate the age of our sun, but I guess is has something to do with the suspected age of our planet. Anyhoo, time for more Christmas music.