unclebobmartin on Nostr: Most of the stars were see in the night sky are extremely luminous giants. Stars the ...
Most of the stars were see in the night sky are extremely luminous giants. Stars the size of our Sun are too faint to be seen beyond a few dozen light years. This is ironic because the Sun is much larger than the majority of stars. There are a vast number of nearby stars that we simply cannot see with the naked eye.
Giant stars burn very hot, and very bright, and for a very short time. A giant can fuse hydrogen into helium thousands of times faster than the Sun. It can exhaust its fuel in as little as ten million years.
In their cores, they first fuse hydrogen into helium, then helium into carbon and oxygen. However, unlike the Sun they are massive enough to continue the process and fuse carbon into a number of other elements, that eventually are fused into silicon
At each stage the rate of fusion must increase because the reactions become less efficient.
On the very last day of a giant star‘s life, it begins to fuse silicon into iron. This reaction is so feeble that the star will burn through a full solar mass of silicon in a matter of hours; all the while a nugget of iron, the size of the Earth, with the mass of the Sun, accumulates in its core.
Fusion reactions with iron are endothermic. They consume energy as opposed to producing it. So when the silicon is exhausted, and the iron begins to fuse under the weight of the star above it, the core cools.
The cooling core collapses, it can no longer produce the energy needed to hold up the mass of the star. The collapse proceeds so rapidly that the material at the center approaches a sizable fraction of the speed of light. The rest of the matter within the star is pulled down with it at a slower pace.
When the core has shrunk to approximately 10 miles in diameter the pressures are so great that the electrons and protons within it are forced to combine into neutrons. This reaction creates a barrage of neutrinos heading outward at the speed of light. Meanwhile the neurons in the core rapidly arrange themselves into an energy shell structure that resists any further collapse. The collapse stops dead.
The outrush of neutrinos carries a vast amount of energy that is more than sufficient to reverse the inflowing matter of the star and blow it out into space at a fraction of the speed of light. This reversal creates temperatures and pressures that stimulate even more fusion within the outrushing guts of the star.
The explosion is so energetic that the dying star’s luminosity increases by approximately twelve orders of magnitude. For several weeks it will outshine the galaxy it lives in.
This is a type 2 supernova, and we don’t want to be close to one. 50 light years is not far enough. Within that radius the radiation slamming into the Earth would be disastrous for life. Fortunately there are no stars within that radius that are likely to blow up soon.
But keep your eye on Betelgeuse — it’s likely to blow in the next few thousand years — maybe tomorrow. At 500 light years it would put on a hell of a show. It would be brighter than the full moon and you could read by it at night.
Giant stars burn very hot, and very bright, and for a very short time. A giant can fuse hydrogen into helium thousands of times faster than the Sun. It can exhaust its fuel in as little as ten million years.
In their cores, they first fuse hydrogen into helium, then helium into carbon and oxygen. However, unlike the Sun they are massive enough to continue the process and fuse carbon into a number of other elements, that eventually are fused into silicon
At each stage the rate of fusion must increase because the reactions become less efficient.
On the very last day of a giant star‘s life, it begins to fuse silicon into iron. This reaction is so feeble that the star will burn through a full solar mass of silicon in a matter of hours; all the while a nugget of iron, the size of the Earth, with the mass of the Sun, accumulates in its core.
Fusion reactions with iron are endothermic. They consume energy as opposed to producing it. So when the silicon is exhausted, and the iron begins to fuse under the weight of the star above it, the core cools.
The cooling core collapses, it can no longer produce the energy needed to hold up the mass of the star. The collapse proceeds so rapidly that the material at the center approaches a sizable fraction of the speed of light. The rest of the matter within the star is pulled down with it at a slower pace.
When the core has shrunk to approximately 10 miles in diameter the pressures are so great that the electrons and protons within it are forced to combine into neutrons. This reaction creates a barrage of neutrinos heading outward at the speed of light. Meanwhile the neurons in the core rapidly arrange themselves into an energy shell structure that resists any further collapse. The collapse stops dead.
The outrush of neutrinos carries a vast amount of energy that is more than sufficient to reverse the inflowing matter of the star and blow it out into space at a fraction of the speed of light. This reversal creates temperatures and pressures that stimulate even more fusion within the outrushing guts of the star.
The explosion is so energetic that the dying star’s luminosity increases by approximately twelve orders of magnitude. For several weeks it will outshine the galaxy it lives in.
This is a type 2 supernova, and we don’t want to be close to one. 50 light years is not far enough. Within that radius the radiation slamming into the Earth would be disastrous for life. Fortunately there are no stars within that radius that are likely to blow up soon.
But keep your eye on Betelgeuse — it’s likely to blow in the next few thousand years — maybe tomorrow. At 500 light years it would put on a hell of a show. It would be brighter than the full moon and you could read by it at night.