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.
Quasars can shine with the brilliance of a trillion suns and astronomers can use this light to silhouette objects nearer Earth. Average galaxies, such as the sunâs home, the Milky Way, can contain 100 billion stars. A light year is the distance light travels in a year in space, about 6 trillion miles.