Physics Question #138
Kay, a 14 year old female from the Internet asks on February 23, 2000,
How can a star become small and dense enough to become a black hole? My understanding is that a neutron star forms when a star collapses and everything is destroyed except its protons and electrons which combine to form neutrons. If a star is big enough, it will crush the neutrons as well, and collapse into nothingness. This is the only way a star can become smaller than a neutron star. If this is so, then how is it possible for a star to become small and dense enough to be a black hole?
viewed 13576 times
answered on February 23, 2000
I think the confusion is in your interpretation of the phrase, "collapse into nothingness." A sufficiently massive neutron star does not stop collapsing when the neutrons get close enough together to see the strong close-range repulsive potential of the neutrons, but just keeps on shrinking to a point; that part is right, but it is wrong to think that because it becomes infinitely small it loses some of its gravitational "oomph". Quite the opposite: in fact, the collapsed object (once called a "collapsar") is just what we mean by a "black hole" -- although of course there are lots of possible complications associated with its spin and electrical charge.
So just remember, a black hole is a collapsed neutron star (or something even heavier). There may be smaller and lighter black holes around too, but they would probably have to be left over from the Big Bang.
Add to or comment on this answer using the form below.
Note: All submissions are moderated prior to posting.
If you found this answer useful, please consider making a small donation to science.ca.