PULSARS
Pulsars, sometimes called neutron stars, are a celestial source of
pulsating radio waves charecterized by a short interval between pulses
and uniformity of the repetition rate of the pulses. The radio signals
are naturally pulsed. Some pulsars stop emitting radio signals then start
up again after a second or a minute.
Pulsars are only around 20 miles across. They are this small because
of their density. They may be
small but they are extremely massive stars. When pulsars were first found,
they raised the hopes for people who believed in black holes. If stars
have collapsed to become such dense stars, they could probably collapse
even further and become even more dense, and become a black hole.