« on: Yesterday at 22:23:48 »
Quote from: syphrum
All the mystery of Black holes stems from the belief that matter cannot be compressed to a higher density than that found in a Neutron star, what is the evidence for this ?The surface density of a neutron star is somewhere around the density of a Lead nucleus (just zillions of times bigger, physically).
If you want to see what happens under higher pressures (like the center of a neutron star), you have to do experiments like smash lead nuclei together in a particle accelerator, and just such experiments are done at the LHC. The problem is that with no gravity to confine the results, the lead nuclei shatter into a cloud of other particles, so physicists have to rely on theory.
One theory is that the "strange" quark might be stable under the immense pressure at the center of a neutron star. The strange quark has much higher mass than the more familiar light quarks making up protons and neutrons. So maybe a "strange star" could be denser than a "neutron star"?
There are a few experiments proposed or underway now that may be able to test these theories on neutron stars and pulsars:
LIGO has detected its first neutron star merger. In this case, the final product became a black hole, rather than a bigger neutron star. With increased sensitivity and more detections, astronomers should be able to place tighter bounds on the size of neutron stars before they collapse into black holes.
I saw a proposed satellite-based experiment measuring the radius and density of neutron stars by studying the spectrum of light emitted by pulsars, with very high resolution in time. By monitoring the red and blue shift, the surface velocity can be measured, and the pulse rate gives the rotation speed. Together, it should be possible to work out the size of the neutron star.
Yet another method proposes to use neutron star seismology to study the interior of neutron stars.
But once the central density of a neutron/strange star reaches a critical value where the escape velocity exceeds the speed of light, current theory suggests that nothing can withstand the plunge into a singularity at the center of a black hole.