Cistus, with its many hybrids and cultivars, is commonly encountered as a garden flower. The common name rockrose is applied to the species, a name also shared by the related genera Halimium, Helianthemum and Tuberaria, all in the family Cistaceae. The common name gum cistus is applied to resin-bearing species, especially C. ladanifer.
Quasars are part of a class of objects known as active galactic nuclei (AGN). Other classes include Seyfert galaxies and blazars. All three require supermassive black holes to power them.
Quasar 3C 273, the brightest and closest of the quasi-stellar radio sources. Courtesy of the National Optical Astronomy Observatories quasar 3C 273, the brightest quasar, photographed by the Hubble Space Telescope's Advanced Camera for Surveys. The black region at the centre of the image is blocking light from the central object, revealing the host galaxy of 3C 273. NASA/STScI/ESA; Learn about this topic in these articles: significance as quasar In quasar: Discovery of quasars â¦pattern of emission lines in 3C 273, the brightest known quasar, could be understood as coming from hydrogen atoms that had a redshift (i.e., had their emission lines shifted toward longer, redder wavelengths by the expansion of the universe) of 0.158.