FU Orionis star
A n FU Orionis star is a pre-main-sequence eruptive variable.
FU Orionis stars appear to be a stage in the development of T
Tauri stars. They gradually brighten by about six magnitudes over several
months, during which time matter is ejected, then remain almost steady or
slowly decline by a magnitude or two over a period of years. All known FU
Ori stars (commonly known as fuors) are associated with reflection
nebulae. The prototype is a cF5- to G3 Ia-type star, presently near
the top of its Hayashi track. In 1936
it suddenly appeared in the middle of a dark cloud, and rose by 6 magnitudes
in the photographic band. Its lithium abundance is 80 times that of the
Sun and it has developed a reflection nebula.
| FU Orionis. Photo: ESO Online Digitized
• variable stars