OH/IR star

OH/IR star

A very large extremely cool giant or supergiant star that is losing mass very rapidly and is detected only by its infrared radiation and by its hydroxyl (OH) maser emission (see maser source). The first OH/IR stars were found in a survey of OH maser sources in 1973; many more were detected by IRAS's infrared survey in 1983. These stars are usually very long period variables. Mira stars often show similar but weaker maser and infrared emission. The OH/IR stars, however, are losing mass a hundred times faster than the Mira stars. They are surrounded by a very dense shell of cosmic dust that shows absorption typical of silicates. The shells have temperatures ranging from 1000 K to only 100 K. Because the stars lose a solar mass of gas and dust in only 10 000 to 100 000 years, they must be changing very rapidly to their next evolutionary state, probably a planetary nebula.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006