Red Supergiant collapse

A type II supernova occurs in stars with greater than 8 solar masses. Successively heavier elements are fused until it reaches iron, where the binding energy is greatest and no more energy can be derived from fusion, at which point gravity wins.

https://en.wikipedia.org/wiki/Nuclear_binding_energy

"The cores of these massive stars directly create temperatures and pressures needed to cause the carbon in the core to begin to fuse when the star contracts at the end of the helium-burning stage. The core gradually becomes layered like an onion, as progressively heavier atomic nuclei build up at the center, with an outermost layer of hydrogen gas, surrounding a layer of hydrogen fusing into helium, surrounding a layer of helium fusing into carbon via the triple-alpha process, surrounding layers that fuse to progressively heavier elements. As a star this massive evolves, it undergoes repeated stages where fusion in the core stops, and the core collapses until the pressure and temperature are sufficient to begin the next stage of fusion, reigniting to halt collapse.^[3][4]"

The onion-like layers of a massive, evolved star just before core collapse. (Not to scale.)

https://en.wikipedia.org/wiki/Type_II_supernova

Really interesting! Now, where are the elements heavier than iron formed?

It use to be the stellar heavier elements formation debate was between the ideas of a parasitic formation in a star where energy was consumed in neutron capture and decays and during a supernova event. (I would assume primordial heavy elements would also be formed by the Big Bang too. An extremely tiny percentage of a truly astronomical number is still a lot of stuff.) Apparently, it is now considered that both stellar processes produce heavier elements. I suspect most of the heavier elements found in planets come from supernova events.

Now, where are the elements heavier than iron formed?

My understanding is that exothermic reactions proceed in the forward direction because one of the output products is energy, which dissipates into the environment. In a supernova explosion, there is enough available energy, an input product of endothermic reactions, that they proceed in the forward direction producing the heavier elements.

"Nuclear fusion reactions that produce elements heavier than iron absorb nuclear energy and are said to be endothermic reactions. When such reactions dominate, the internal temperature that supports the star's outer layers drops. Because the outer envelope is no longer sufficiently supported by the radiation pressure, the star's gravity pulls its mantle rapidly inward. As the star collapses, this mantle collides violently with the growing incompressible stellar core, which has a density almost as great as an atomic nucleus, producing a shockwave that rebounds outward through the unfused material of the outer shell. The increase of temperature by the passage of that shockwave is sufficient to induce fusion in that material, often called explosive nucleosynthesis.^[2][20] The energy deposited by the shockwave somehow leads to the star's explosion, dispersing fusing matter in the mantle above the core into interstellar space."

https://en.wikipedia.org/wiki/Supernova_nucleosynthesis

Who’s says so,… Betelgeuse may have already collapsed…

Possible, but not likely. The ~600 years since light left Betelgeuse is a mere instant in the life of a star, even a giant star.

Seeing it explode would be quite a sight, but unfortunately, it's highly unlikely anyone alive now will see it.

You so you’re saying it’ll be a while and that I should bring a chair…

You really must like raining on my parade,…

Sorry, yes. On the other hand, I've always liked the Orion constellation, and blowing up Betelgeuse would kind of mess it up.

I feel the same way with the Milky Way, with it as a spiralgalaxy, that is, it’s orderly and pleasing and some what symmetrical.

and now entering the impending collision (so to speak) with the Andromeda Galaxy is going to really mess that up… but I try not to let this keep me up at night…

sorry about the distraction…

When does that time scale start? Now or 4 billion years ago?

Yes, and yes,… Doesn’t matter,… it already started… You can’t stop it, it’s happening…

"Milkomeda"?