(This goes along with Brant's "Suppose there is no such thing as a singularity?") Another Black hole question

Question

I've read in books that they suppose in order to make earth a black hole we would suppress it to a size of a penny, but why size would a star that are billions the size of our earth need to be suppressed down to a grain of dust, shouldn't it be bigger than a coin due to the higher mass?

Answer 1

Apples and oranges.  A mass like the sun would have to shrink down to about 3 km (radius) to become a black hole. A grain of dust for that kind of mass would just be a denser black hole.  I guess you were referring to my comment that I didn't believe a singularity could actually exist, but rather the shrinkage could only approach being one.

One thing I find interesting is that the sun is about 100 times the diameter of the earth, yet the size of the sun's mass which would become a black hole is 600,000 times the size at which the earth's mass would become one.

Answer 2

Stars are as big as they are because nuclear fusion releases energy, in the form of heat, which expands them.

When nuclear fusion stops in our Sun, it will eventually become a white dwarf - held up by electrostatic forces.  It will be about the size of the Earth, but with much of the Sun's mass.  Very dense.

Bigger stars leave a more massive corpse - a neutron star.  These stars are too heavy for electrostatic forces, and are compressed to a neutron soup.  They're more massive than the Sun, and are the size of a big city.

Bigger stars yet can leave even a more massive corpse - a quark star.   Even higher compression - they are a quark soup.  Really tiny, but i've no idea how big.  We've just recently found evidence of big supernovae, called hypernovae, which may lead to quark stars.  Maybe we'll get to study object of this type soon.  That would be cool.

Bigger stars yet can leave something so massive that they collapse to a point - a singularity, a black hole.  The mass is so huge that not even light can escape their gravity.  What's inside?  All the mass is there.  But even the quarks are superimposed on each other, more or less all in one spot.  But we really don't know for sure what's in there.  Oddly, the star's magnetism seems to be conserved.  Black holes generally have very powerful magnetic fields. What generates them?

Of interest is that proxima centauri, the closest red dwarf star, has had it's diameter measured.  It's much more massive than Jupiter, but it's about the same size.  More mass, just squished down.  In fact, Jupiter is about as big as gas giant planets can get.  Add more mass and it shrinks.

Answer 3

A 2 solar mass star compressed to a 3 km diameter sphere would be a black hole.

  If the earth were compressed to a black hole it would be about one-tenth of a mm in diameter.

  There are several very good reasons why black holes are non viable entities.

Answer 4

what if there is no such thing as a black hole. human eyes vision is processed by our brain. it tries to make sense of what we see. if we have no info on something then wouldn't we come up with reasoning based on what we have learned?  Einstein's cross, could that have been reflection?  i really don't know,