Could you answer me about this excerpt I found on a book I read?
“We are supposed to believe that the depleted remains of the star collapses into an extremely dense pellet that has such a high gravitational pull that light cannot escape from it and that its gravitational pull can suck in much heavier active stars and eventually form much bigger and more dangerous black holes. I do not understand how they can justify that a burnt-out star that has suffered a substantial loss of mass and size can create a super gravitational force with amazing space-time properties. I have never heard of gravity being affected by density instead of by mass.”
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What’s the question? Gravity is affected by the RATIO of density to mass. It is the fact that a stupefying mass is concentrated in a miniscule space which renders the black hole possible.
No I cannot, or rather I will not bother. You can easily find the mechanics on black holes. I am more concerned that you bother with the subject from the perspective of someone who doesn’t understand the basics. For instance, the writer misses the point that the “much heavier massive star” and the black hole pull on one another. The mass of the larger star can only be transferred to the hole when the 2 are within a critical distance of one another as they effectively circle one another.
The collapsed star has not lost mass. It has been condensed due to the stronger and stronger gravitational field that is being created by the star’s collapse, and it’s continuing collapse.
I think he is referring to the material blown off with the supernova initiating the collapse.
You might have luck looking for “Chandrasekhar Limit In Astrophysics.”
In a star, gravity compresses the immense mass together so strongly that it causes nuclear fusion reactions, which release immense amounts of energy, which creates outward pressure that prevents further collapse. But the reactions change the matter into different forms which have different properties. That changes the situation. Some of those situations eventually lead to conditions where the reactions do not have enough fuel left to produce enough energy to keep the mass of the star at its current size, so at that point the star collapses, leading to new conditions which can eproduce an explosion (nova), dwarf star, or black hole.
Or, as worded by NASA: https://imagine.gsfc.nasa.gov/educators/lessons/xray_spectra/background-lifecycles.html
It is an odd book that says things like “we are supposed to believe” and “I do not understand” when the formation of black holes is well understood and has been described in numerous other publications.
Not all stars will turn into black holes. They need to have a minimum amount of mass.
NASA identifies the smallest known black hole . It is 3.8 times the mass of our sun.
Here is a 10 year time lapse video of stars orbiting around the massive black hole in the center of our own galaxy. From the star trajectories the mass of the black hole can be calculated. It has the mass of approx 4.5 million of our Sun. The black hold is called Sagittarius A
You can do a quick search and find other videos with stars named, orbits clearly marked, simulations of other stars, gas clouds, etc.
I wonder what it would be like to live on a planet orbiting around one of those stars as it whips around the black hole. Would we notice? Would we adjust like we adjust to the seasons?
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