| Subject |
has expansion velocity |
is a kind of |
has catalog |
has wavelength |
is an instance of |
has synonym |
has definition |
has distance |
|---|
| radio source | | celestial body | radio source catalog | radio | | | A source of extraterrestrial radio radiation. The strongest known is Cassiopeia A, followed by Cyg A and the Crab Nebula (Tau A) (the capital letters following the name of a constellation refer to the radio sources of the constellation, A being the strongest source). Radio sources are divided into two main categories: Class I, those associated with our Galaxy (which is a weak radio source), and Class II, extragalactic sources. Most radio sources are galaxies, supernova remnants, or H II regions. | |
| X-ray source | | celestial body | | X-ray | | | A class of celestial objects whose dominant mechanism of energy dissipation is through X-ray emission. Galactic X-ray sources appear optically as starlike objects, peculiar in their ultraviolet intensity, variability (on time scales ranging from milliseconds to weeks), and spectral features. All known compact X-ray sources are members of close binary systems; a current popular model is mass accretion onto a compact object from a massive companion. (Four X-ray sources - all variable - are known to be associated with globular clusters.) The 21 known extended X-ray sources associated with clusters of galaxies seem to be clouds of hot gas trapped in the cluster's gravitational field. | |
| Cassiopeia A | 800 km s-1 | | radio source catalog | X-ray | X-ray source | 3U 2321+58 | A radio source in Cassiopeia, the strongest extrasolar source in the sky, believed to be the remnant of a Type II supernova whose light reached Earth about 1667. Optically it is a faint nebula. It has a mass of a few solar masses. It is also an extended source of soft X-rays. | 3 kpc |
Astronomy View all facts Glossary Help
