Physical theory predicts neutron stars. Are they there?
- Mass around 2 solar masses
- M > 1.4 Msun because of Chandrasekar limit.
The density is about 1018 kg/m3. That is
1015 times the density of water. The neutrons are squeezed
until they are just about touching each other. That is, they are squeezed by
a factor of 105 in each direction.
(Recall the sizes of atoms and nulcei).
- M < 3 Msun because new limit where size appears
to go to zero but theory says we need to account for general relativity.
Jocelyn Bell's discovery in 1967
Interpretation (to be discussed later in this class)
- Antony Hewish (Cambridge) builds radio telescope able to detect faint rapidly varying signals.
- Jocelyn Bell Burnell, graduate student, notices unusual signals.
- A radio transmission from intelligent life? What is going on?
- Careful investigation reveals:
- regular pulses (one every 1.3373011 seconds).
- source fixed with respect to the stars.
- other similar sources found. Periods of
- 0.253065 s
- 1.187911 s
- 1.273763 s
- The objects are neutron stars.
- They are rapidly rotating.
- They are emitting a beam of radio waves that points toward Earth
once each rotational period.
Davison E. Soper, Institute of Theoretical Science,
University of Oregon, Eugene OR 97403 USA