Neutron Stars

Physical theory predicts neutron stars. Are they there?

• Mass around 2 solar masses
  • M > 1.4 M_sun because of Chandrasekar limit.
  • M < 3 M_sun because new limit where size appears to go to zero but theory says we need to account for general relativity.
  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).

  Jocelyn Bell's discovery in 1967

  • 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
  Interpretation (to be discussed later in this class)
  • 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 soper@bovine.uoregon.edu