NOTABLE STARS 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 CH Cygni The nebula around CH Cygni imaged by the 2.6m NOT telescope of La Palma. Credit: Villaver, Corradi, and Mampaso The brightest and one of the most unusual known symbiotic stars; it lies in the constellation Cygnus, 2° south-southwest of Iota Cygni at a distance of about 870 light-years. CH Cygni has ranged in brightness from magnitude 5.6 (visible to the naked eye) to 10.5. It was originally thought to be a semi-regular variable, with a 90- to 100-day period and an amplitude of about one magnitude. However, in 1976 a hot blue continuum appeared in the spectrum, together with emission lines of hydrogen, helium, calcium, and iron; at the same time, CH Cygni grew brighter than it had ever been seen before and showed rapid fluctuations, especially in ultraviolet light. This superposition of two distinct spectra – a hot blue continuum with emission lines on top of a late-type absorption spectrum – led to CH Cygni’s reclassification as a symbiotic star. It is thought to consist of an M-type red giant and a much hotter, smaller star, possibly a white dwarf, in a 2.07-year orbit. The pair are embedded in a dusty cloud of material that has been pulled off the giant by the hot dwarf; there also appears to be a third star in a wider, 14.5-year orbit. CH Cygni remained in its "blue outburst" state from 1976 to 1986, then faded abruptly by about 2.5 magnitudes. Subsequently it continued to fade, reaching an all-time low magnitude of 10.5 in 1997. However, the decline wasn't smooth and there were semi-periodic oscillations with each minimum fainter than the last. Since 1997, CH Cygni has varied between magnitudes 7.7 to 9.1. In 1984, radio emission was detected in the CH Cygni system, further studies of which revealed a bipolar jet-like structure. Although the physical mechanism of jet formation in symbiotic systems are still poorly understood, one possibility is that CH Cygni’s jet is ejected from an accretion disk around the hot companion. Related categories    • NOTABLE STARS    • VARIABLE STARS Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP