Definition of Keyhole Nebula in English:

Keyhole Nebula

See synonyms for Keyhole Nebula

noun

Astronomy
  • (The name of) a small nebula in the southern sky surrounding the variable star η Carinae, with a dark central region shaped like a keyhole.

    η Carinae was formerly called η Argus.

Origin

Late 19th century; earliest use found in The Eclectic Magazine.