Introduction to general relativity this energy loss would be too small to be detectable, but this energy loss was observed in 1974 in a binary pulsar called PSR1913+16. In such a system, one of the orbiting stars is a pulsar. This has two consequences: a pulsar is an extremely dense object known as a neutron star, for which gravitational wave emission is much stronger than for ordinary stars. Also, a pulsar emits a narrow beam of electromagnetic radiation from its magnetic poles. As the pulsar rotates, its beam sweeps over the Earth, where it is seen as a regular series of radio pulses, just
Relativistic beaming accreting compact object, but are thought to be merely a particular variety of AGN.) Beaming (short for relativistic beaming) affects the apparent brightness of a moving object just as a lighthouse affects the appearance of its light source: the light source appears dim or unseen to a ship except when the rotating lighthouse beacon is directed towards a ship, where it then appears very bright. This so-called lighthouse effect illustrates how important the direction of motion (relative to the observer) is in relativistic beaming: if a blob of gas emitting electromagnetic radiation is moving towards the observer then it will