|Observation data: J2000 epoch|
|Right ascension||04h 42m 53.64s|
|Declination||+36° 06′ 53.4″|
|Designations||CRL 618, IRAS 04395+3601, 2MASS J04425364+3606534, RAFGL 618|
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.
- "Westbrook Nebula -- Post-AGB Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2009-04-16.
- Christensen, Lars Lindberg; Tielens, A.G.G.M. (2000-08-31). "A stellar cocoon soon to hatch to a butterfly". European Space Agency. Retrieved 2013-06-12.
- Westbrook, W. E.; Gezari, D. Y.; Hauser, M. G.; Werner, M. W.; Elias, J. H.; Neugebauer, G.; et al. (1976). "One-millimeter continuum emission studies of four molecular clouds". Astrophysical Journal. 209: 94–101. Bibcode:1976ApJ...209...94W. doi:10.1086/154695.
- Contreras, C. S.; Sahai, R.; Gil de Paz, A. (October 2002). "Physical structure of the protoplanetary nebula CRL618. I. Optical long-slit spectroscopy and imaging". Astrophysical Journal. 578 (1): 269–289. Bibcode:2002ApJ...578..269S. arXiv: . doi:10.1086/342316.