A Pulsar (from Pulsating Star) is an astronomical object that cycles between more and less radiation on a time scale of a few seconds or less, the fastest having a cycle of a few milliseconds. The cycles are very precise, like clockwork. They are unresolved point sources, like stars.
They are assumed to be rotating, sending a beam of Electromagnetic Radiation (EMR) that sweeps a circle, hitting Earth, like a rotating beacon or lighthouse light. They are further assumed to be Neutron Stars and their beam caused by the effects of a rotating magnetic field. A rationale is that a rotation of hundreds of times a second implies a small object able to affect a sufficiently-strong EMR source, e.g., a neutron star.
The first pulsar observation was in 1967, being nicknamed LGM-1 ("little green men 1" because the clockwork Frequency of pulses suggested an artificial source), later officially named CP 1919, then PSR B1919+21. Today there are over a thousand known pulsars.
The remarkably consistent cycles and the high density of the neutron stars offer astrophysicists unique opportunities for testing and observing physical phenomena such as the influence of Gravitational Waves (GW).
An X-ray Pulsar (i.e., Binary X-ray Pulsar) is a neutron star with an exceptionally strong magnetic field accreting matter from its companion star (which is not a neutron star), whose magnetic poles are misaligned with its spin. The material is channeled to a circular-moving magnetic pole, and the shock heating produces X-rays directed along the axis of the magnetic poles.
Active Galactic Nucleus (AGN)
Black Widow Pulsar (B1957+20)
European Pulsar Timing Array (EPTA)
Extra Solar Planet
Galactic Electron Density
Green Bank 140 Foot Telescope
Gravitational Wave (GW)
International Pulsar Timing Array (IPTA)
Crab Nebula (M1)
Millisecond Pulsar (MSP)
Nanohertz Gravitational Waves
Parkes Pulsar Timing Array (PPTA)
Hulse-Taylor Binary (PSR B1913+16)
Pulsar Timing Array (PTA)
Refractive Interstellar Scintillation (RISS)