Right ascension 04 42 53.64 Constellation Auriga | Declination +36° 06′ 53.4″ | |
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Designations CRL 618, IRAS 04395+3601, 2MASS J04425364+3606534, RAFGL 618 Similar Egg Nebula, CW Leonis, NGC 7027, Calabash Nebula, Frosty Leo Nebula | ||
Westbrook Nebula (CRL 618) is an aspherical protoplanetary nebula which is located in the constellation Auriga. It is being formed by a star that has passed through the red giant phase and has ceased nuclear fusion at its core. This star is concealed at the center of the nebula, and is ejecting gas and dust at velocities of up to 200 km/s. The nebula is named after William E. Westbrook, who died in 1975.
This nebula began to form about 200 years ago, and primarily consists of molecular gas. The outer part of the nebula is the result of interaction between rapid bi-polar outflow and the gas that was ejected when the star was passing through its asymptotic giant branch phase. The lobes are inclined about 24° to the line of sight. The energy being radiated from the nebula consists of scattered light from the star at the core, light being emitted from a compact HII region surrounding the star, and energy from the shock-excited gas in the lobes.
The core star is believed to be of spectral class B0 and has 12,200 times the solar luminosity.