Compact Stars: Nuclear Physics, Particle Physics, and General Relativity (Astronomy and Astrophysics Library)

Rating:
Summary: A very interesting but advanced textbook
Review: Compact stars are fascinating objects. It is sad that it is difficult to adequately explain many of their properties in a book for the layman. This book does a great job, but it is basically a textbook for graduate students.

This book does review the fundamentals of compact stars. It shows the evidence that the source of energy for a supernova is the binding energy of a neutron star (that binding energy is about ten per cent of the mass).

Compact stars are relativistic, the book teaches us General Relativity, in what I consider a very readable and instructive chapter. The Oppenheimer-Volkoff equations are then derived to obtain the gravitational mass and pressure gradient for a static and spherically symmetric compact star. We're also reminded of a famous test of General Relativity provided by the Hulse-Taylor pulsar binary discovered in 1974. That test found a decay in the orbital period of 0.76 microseconds per year, agreeing to within a percent of the calculations of energy loss through gravitational radiation predicted by General Relativity: convincing evidence if you ask me!

And we're reminded that some of these compact stars rotate at very high rates. And that objects falling towards them starting at rest from a great distance fall not towards the center of the star but instead acquire ever larger angular velocities as they approach.

After that we learn some theoretical basics about white dwarves and neutron stars, their temperatures, the stellar sequences that produce them, and black holes.

Next we find we need to learn some Lagrangian Field Theory, so that we can try to derive a relativistically covariant theory of dense hadronic matter (the likely constituent of neutron stars). We learn about sigma-omega models and the isospin force. And the author also gets to the question of whether neutron matter is bound or unbound. While neutron stars are clearly bound by gravity, not the nuclear force, the issue is whether there is a bound state of neutron matter at any density. If so, then the surfaces of neutron stars are, well, neutrons, rather than some overlying layer of matter at subnuclear density.

There's a section on the observational evidence for neutron stars, namely pulsar observations. And then we get into the constitution (including the hyperon density) and phase transitions in neutron stars, followed by an extensive discussion of rotating neutron stars.

There's a discussion of pulsar "glitches" which are hypothesized to be starquakes, caused by deceleration-induced stress on the crust of the star. I wish Glendenning had said more about an additional possibility, namely that the star is a rotating neutron superfluid, penetrated by an array of vortex lines, and that the glitches are transitions between metastable states of the vortex array. There are also analogies with experiments done on superfluid liquid helium that support this, so I was hoping to see a discussion of it. Either way, the glitches seem to imply the existence of a crust, ruling out theories of a bound state of neutron matter.

Finally, we've gotten to the fun stuff: quark stars. After all, quarks are the constituents of nucleons, and they're asymptotically free. So are there hybrid stars, with quark matter in the central region and a nuclear matter mantle? That gets us into our introduction to the concept of strange and charm stars, and the MIT bag model of quark confinement. And at the end of the book, we see discussions of the structure of strange quark stars. This is an exciting field, as observations of sub-millisecond pulsars would imply the existence of these strange quark stars. That in turn would imply that the actual ground state of the stong interaction is not quarks confined in hadrons but deconfined strange quark matter. In short. "it would tell us that the universe is in a very long-lived but excited state."

This is a very interesting book, and it is a shame that it requires so much background material to appreciate it.