A revised historical light curve of Eta Carinae and the timing of close periastron encounters

Nathan Smith, David J. Frew

Research output: Contribution to journalArticlepeer-review

83 Scopus citations


The historical light curve of the 19th century 'Great Eruption' of η Carinae provides a striking record of the violent instabilities encountered by massive stars. In this paper, we report and analyse newly uncovered historical estimates of the visual brightness of η Car during its eruption, and we correct some mistakes in the original record. The revised historical light curve looks substantially different from previous accounts; it shows two brief precursor eruptions in 1838 and 1843 that resemble modern supernova impostors, while the final brightening in 1844 December marks the time when η Car reached its peak brightness. We consider the timing of brightening events as they pertain to the binary system in η Car. (1) The brief 1838 and 1843 events rose to peak brightness within weeks of periastron passages if the pre-1845 orbital period was ∼5 per cent shorter than that at present due to the mass-loss of the eruption. Each event lasted only ∼100d. (2) The main brightening at the end of 1844 has no conceivable association with periastron, beginning suddenly more than 1.5yr after periastron. It lasted ∼10yr, with no obvious influence of periastron encounters during that time. (3) The 1890 eruption began to brighten at periastron, but took over 1yr to reach maximum brightness and remained there for almost 10yr. A second periastron passage mid-way through the 1890 eruption had no visible effect. While the evidence for a link between periastron encounters and the two brief precursor events is compelling, the differences between the three cases above make it difficult to explain all three phenomena with the same mechanism.

Original languageEnglish (US)
Pages (from-to)2009-2019
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Aug 2011


  • Binaries: close
  • Instabilities
  • Stars: individual: Eta Carinae
  • Stars: mass-loss
  • Stars: massive

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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