Neutron stars are small (about 20km across), rotate rapidly and are incredibly dense. They are mostly made of neutrons that formed as electrons combined with protons in the atomic nuclei of the dying stars' collapsing cores. Their powerful magnetic fields lead to radio pulses that can be detected on the Earth each time they rotate. These objects are known as pulsars when the pulses can be detected on the Earth.
Image: The Vela pulsar jet (credit: NASA/CXC/PSU/G.Pavlov et al.)
Pulsars send signals across the Universe.
Patrick Moore discusses supernovae and the famous Crab.
Sir Patrick Moore and his guest Professor Sir Francis Graham-Smith discuss supernovae that create clouds of gas like the famous Crab Nebula.
Andrew Lyne explains why astronomers study neutron stars.
Sir Patrick Moore and his guest Professor Andrew Lyne discuss what neutron stars are and why we study them.
Kathy Sykes talks to Jocelyn Bell Burnell about her discovery.
As a student at Cambridge, Jocelyn Bell Burnell discovered pulsars using a radio telescope. Pulsars are rapidly rotating neutron stars whose regularly occurring energy pulses are detected by astronomers on the Earth.
Jocelyn Bell, interviewed in 1971, describes her discovery.
Jocelyn Bell (now Jocelyn Bell Burnell), interviewed in 1971, describes how she discovered pulsars. Her supervisor, Anthony Hewish, later shared a Nobel prize with Martin Ryle for their work in radio astronomy. Controversially, Bell Burnell did not share the prize.
Patrick Moore listens to pulsars at Jodrell Bank.
Sir Patrick Moore listens to pulsars at Jodrell Bank Observatory.
A pulsar (portmanteau of pulsating star) is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. This radiation can only be observed when the beam of emission is pointing toward the Earth, much the way a lighthouse can only be seen when the light is pointed in the direction of an observer, and is responsible for the pulsed appearance of emission. Neutron stars are very dense, and have short, regular rotational periods. This produces a very precise interval between pulses that range from roughly milliseconds to seconds for an individual pulsar.
The precise periods of pulsars make them useful tools. Observations of a pulsar in a binary neutron star system were used to indirectly confirm the existence of gravitational radiation. The first extrasolar planets were discovered around a pulsar, PSR B1257+12. Certain types of pulsars rival atomic clocks in their accuracy in keeping time.