TYPES OF STAR STELLAR ASTROPHYSICS A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z                    HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site X-ray nova Artist's representation of an X-ray nova. The compact object on the right – a neutron star or a black hole – accretes gas from a normal companion star. The gas swirls in a disk around the compact object at very high velocity close to the speed of light from where it emits X-rays. Credit: ESA A short-lived X-ray source that appears suddenly in the sky and dramatically increases in strength over a period of a few days and then decreases, with an overall lifetime of a few months; it may have an optical counterpart. Unlike a conventional nova, in which the compact component is a white dwarf, an X-ray nova may be caused by material falling onto a neutron star or a black hole. Related entry    • X-ray transient Related categories    • TYPES OF STARS    • STELLAR ASTROPHYSICS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP