Pan-starrs 1 observations of the unusual active centaur P/2011 S1(Gibbs)

H. W. Lin, Y. T. Chen, P. Lacerda, W. H. Ip, M. Holman, P. Protopapas, W. P. Chen, W. S. Burgett, K. C. Chambers, H. Flewelling, M. E. Huber, R. Jedicke, N. Kaiser, E. A. Magnier, N. Metcalfe, P. A. Price

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9 Scopus citations


P/2011 S1 (Gibbs) is an outer solar system comet or active Centaur with a similar orbit to that of the famous 29P/Schwassmann-Wachmann 1. P/2011 S1 (Gibbs) has been observed by the Pan-STARRS 1 (PS1) sky survey from 2010 to 2012. The resulting data allow us to perform multi-color studies of the nucleus and coma of the comet. Analysis of PS1 images reveals that P/2011 S1 (Gibbs) has a small nucleus <4 km radius, with colors g P1 rP1 = 0.5 ± 0.02, r P1iP1 = 0.12 ± 0.02, and i P1 zP1 = 0.46 ± 0.03. The comet remained active from 2010 to 2012, with a model-dependent mass-loss rate of ∼100 kg s -1. The mass-loss rate per unit surface area of P/2011 S1 (Gibbs) is as high as that of 29P/Schwassmann-Wachmann 1, making it one of the most active Centaurs. The mass-loss rate also varies with time from ∼40 kg s -1 to 150 kg s-1. Due to its rather circular orbit, we propose that P/2011 S1 (Gibbs) has 29P/Schwassmann-Wachmann 1-like outbursts that control the outgassing rate. The results indicate that it may have a similar surface composition to that of 29P/Schwassmann-Wachmann 1. Our numerical simulations show that the future orbital evolution of P/2011 S1 (Gibbs) is more similar to that of the main population of Centaurs than to that of 29P/Schwassmann-Wachmann 1. The results also demonstrate that P/2011 S1 (Gibbs) is dynamically unstable and can only remain near its current orbit for roughly a thousand years.

Original languageEnglish
Article number114
JournalAstronomical Journal
Issue number5
StatePublished - May 2014


  • Kuiper belt objects: individual (Centaur asteroid)
  • comets: general


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