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
Tractor beam Intended applications include remotely manipulating space objects at distances up to about 100 km, removal of space debris, and retrieval of adrift astronauts or tools on-orbit. In March 2011, Chinese scientists posited that a specific type of Bessel beam (a special kind of laser that does not diffract at the centre) is capable of creating a pull-like effect on a given microscopic particle, forcing it towards the beam source. The underlining physics is the maximization of forward scattering via interference of the radiation multipoles. They show explicitly that the necessary condition to realize a negative (pulling) optical force is the