Cleaning up η Carinae: Detection of ammonia in the Homunculus Nebula

Nathan Smith, Kate J. Brooks, Bärbel S. Koribalski, John Bally

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


We report the first detection of ammonia in the Homunculus Nebula around η Carinae, which is also the first detection of emission from a polyatomic molecule in this or any other luminous blue variable (LBV) nebula. Observations of the NH3 (J, K) = (3, 3) inversion transition made with the Australia Telescope Compact Array reveal emission at locations where infrared H2 emission had been detected previously, near the strongest dust emission in the core of the Homunculus. We also detect ammonia emission from the so-called strontium filament in the equatorial disk. The presence of NH 3 around η Car hints that molecular shells around some Wolf-Rayet stars could have originated in prior LBV eruptions, rather than in cool red supergiant winds or the ambient interstellar medium. Combined with the lack of any CO detection, NH3 seems to suggest that the Homunculus is nitrogen-rich like the ionized ejecta around η Car. It also indicates that the Homunculus is a unique laboratory in which to study unusual molecule and dust chemistry, as well as their rapid formation in a nitrogen-rich environment around a hot star. We encourage future observations of other transitions like NH3 (1, 1) and (2, 2), related molecules like N2H +, and renewed attempts to detect CO.

Original languageEnglish (US)
Pages (from-to)L41-L44
JournalAstrophysical Journal
Issue number1 II
StatePublished - Jul 1 2006


  • Astrochemistry
  • Circumstellar matter
  • ISM: molecules
  • Stars: mass loss
  • Stars: winds, outflows

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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