The shocking near-infrared spectrum of the Homunculus Nebula surrounding η Carinae

Nathan Smith, Kris Davidson

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Near-infrared long-slit spectra of the Homunculus Nebula surrounding η Carinae reveal emission from molecular hydrogen for the first time in this object, as well as strong intrinsic [Fe II] emission. H2 emission is seen only in the polar lobes of the Homunculus, which show v = 1-0 emission in the K band, but no v = 2-1 emission. The strengths of certain [Fe II] lines are enhanced in the same regions of the polar lobes as the H2 emission, where [Fe II] 1.6435 μm is by far the brightest near-infrared line emitted in the Homunculus Nebula. The intrinsic spectrum of the northwest polar lobe resembles the near-infrared spectra of some supernova remnants, and shock excitation is required to explain the strengths of the [Fe II] and H2 lines. Shock-excited emission in the polar lobes suggests that the central star has a fast bipolar wind and a slower equatorial wind. The H2 lines observed in these spectra represent the first detection of any molecular gas in the Homunculus Nebula, which has important implications for the density structure in the polar lobes and in the stellar wind during and after the Great Eruption.

Original languageEnglish (US)
Pages (from-to)L101-L104
JournalAstrophysical Journal
Issue number1 PART 2
StatePublished - Apr 10 2001

Bibliographical note

Funding Information:
We thank Brooke Gregory, Patrice Bouchet, and Hernan Tirado for their assistance with the OSIRIS observations, and we thank the staff at La Serena for their hospitality. During our observing run, Edguardo Cosgrove was kind enough to let us view h Car through the eyepiece of the Lowell telescope on Cerro Tololo, which is a rewarding experience since h Car’s recent brightening. N. S. is grateful for the support of a NASA GSRP fellowship from Goddard Space Flight Center, as well as travel to Chile and accommodations paid for by NOAO.

Funding Information:
1Visiting Astronomer, Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatories, operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.


  • Circumstellar matter
  • Stars: individual (η Carinae)


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