Radio-quiet neutron star ten bodies have been proposed as rotation-powered neutron stars that are not visible as radio sources, but are visible as x–ray and gamma ray sources. Indicators that they are indeed neutron stars include them having a high x-ray to lower frequencies emission ratio, a constant x-ray emission profile, and coincidence with a gamma ray source. Quark stars, theoretical neutron star-like objects composed of quark matter, may be radio quiet, according to some theories. More plausibly, however, radio-quiet neutron stars may simply be pulsars which do not pulse in our direction. As pulsars spin, it is theorized they emit radiation from
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