Orion Nebula
astronomy
(catalog numbers NGC 1976 and M 42), bright diffuse nebula, faintly visible to the unaided eye in the sword of the hunter's figure in the constellation Orion. The nebula lies about 1,350 light-years from Earth and contains hundreds of very hot (O-type) young stars clustered about a nexus of four massive stars known as the Trapezium. Radiation from these stars excites the nebula to glow. It was discovered in 1610 by the French scholar Nicolas-Claude Fabri de Peiresc (Peiresc, Nicolas-Claude Fabri de) and independently in 1618 by the Swiss astronomer Johann Cysat. It was the first nebula to be photographed (1880), by Henry Draper (Draper, Henry) in the United States.Images of the nebula continued to improve, and technological advances in the late 1980s enabled scientists to photograph infrared-emitting objects in the Orion Nebula that had never before been observed optically. The Hubble Space Telescope in 1991 revealed the sharpest details yet available of known features of the nebula, including what appeared to be a jet (an energetic outflow) related to the birth of a young star.
- Excelsior diamond
- Excelsior Springs
- excess-profits tax
- exchange, bill of
- exchange control
- exchange marriage
- exchange rate
- Exchequer
- excitation
- exciton
- exclusionary rule
- Exclusions of paternity on the ABO system
- Exclusive
- excommunication
- excretion
- executive agreement
- executor
- exedra
- exegesis
- Exekias
- exemplum
- exercise
- exercise-induced pulmonary hemorrhage
- Exe, River
- Exeter