Here is the plan as we see it now, it is, of course, subject to
revision as the course progresses.
The first evidence for neutron stars
was uncovered during the sixties. The stability and frequency of radio
pulsars alone was sufficient to make a convincing argument that they
were neutron stars.
I encourage you to follow check out this interesting take on the discovery
of pulsars: A Science Odyssey: On The Edge: Little Green Men. Also see how the birth of x-ray astronomy has affected our everyday life at AS&E.
The first neutron stars to be positively identified are the rotation-powered
neutron stars, specifically the radio pulsars. The most famous of the radio
pulsars is the source at the center of the Crab supernova remnant, the Crab
pulsar. The emission from these neutron stars is powered by the rotation
of the neutron star coupled to electromagnetic radiation through the magnetic
dipole moment of the star.
Check out this
Java Applet that simulates the electric field from a moving
charge.
ATNF Pulsar Catalog
and the sounds of pulsars at Princeton Pulsar Group.
Neutron stars are truly relativistic objects. You cannot understand
their structure without general relativity and nuclear physics. The
key observational quantities that probe this physics are the mass and
radius of neutron stars. You can explore some more and less realistic
equations of state using the Mass-Radius
Relation Applet and the Neutron-Star
Structure Applet.
Neutron stars are born in the fiery explosion of a supernova. Although
they are cold in the sense that the Fermi temperature is much greater than
the thermodynamic temperature except in the outermost layers, neutron stars
radiate like any hot bodies. In fact their interiors and crusts radiate
neutrinos and their surfaces radiate soft x-rays. These soft x-rays are some
of the few direct data that we get from neutron stars.
Many neutron stars are paired with other stars and accrete from their
companions. How a neutron star accretes is an interplay between the magnetic
field of the neutron star, the evolution of the orbit and the properties
of the companion star.
The discovery of planets orbiting other stars is one of the most exciting discoveries of the past decade and a half.
I have attached homework due Friday. Becasue of the extension of the last set, I made this set only two problems.
Also attached: Peebles and Yu (1970). Even I was not yet a physicist when this was written. The paper talks about clumping on different mass scales, but it is now looked at as the first paper to sort out what the source of anisotropy of the CMB is. Read it for Thursday morning.
I'd like to offer advice on the sorts of questions you should be thinking about as you read. The detailed ones are great: what are the units of Figure 3? What is a chemical potential?... but also ask some broader ones. I have in mind
What is the main result?
For example, the main result of the Mather paper is that the universe was in good thermal equilibrium when it was hot enough to make e+ e- pairs.
Why did this happen when it did, not before or after?
What did this result allow to happen next? ie Who needed this?
I am reminded of an essay I read by Louis Alvarez, inventor of the bubble chamber. He said when he learned something new he asked himself five questions.
- Do I believe this?
- How do I know it?
- Does it contradict anything else I believe?
- What does it imply?
- Do I believe this?
I can not promise that you will all win Nobel prizes if you ask those sorts of questions, but I'll take credit if you do!
Mark Halpern
Last modified: Thursday, 08 April 2010 14:15:28
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