1. Neutron Star

2. Gravitational Crush The balance point to maintain degenerate matter is 1.4 M . When the mass of the core is greater than 1.4 M , electrons cannot support the gravitational force. This is the Chandrasekar limit: beyond that it’s supernova. white dwarf supernova

3. With the pressure and temperature electrons can fuse with protons into neutrons. Degenerate matter is already compressed, but there are both electrons and nuclei. electron nucleus proton neutron Neutrons neutrons only - fewer particles

4. Neutron Core The packed neutrons remain and become a neutron star. –Very hot: 200 billion K –Very small: 10 - 30 km, the size of De Kalb county –Very dense: 100 million tons per cm 3

5. Surface Gravity Surface gravity is proportional to the mass divided by the radius squared. –M ns = M , about 10 6 M earth. –R ns = 0.003 R earth. –The surface gravity, g ns = 10 11 g earth.

6. X-rays The surface gravity creates tremendous accelerations. –Photons from accelerating electrons –X-rays from high energy X-ray telescopes in orbit can spot neutron stars in supernova remnants.

7. Pulsars Neutron stars create very large magnetic fields. –Increased spin from collapse –Spin up to 30 Hz (30 times per second) These pulsars can be observed as repeating flashes of light as the magnetic poles point towards us.

8. X-ray Pulsars Pulsars also emit x-rays. –Appear to blink as pulsar spins –Time between blinks = period of the pulsar crab nebula offcrab nebula on