Pan-STARRS 1 observations of the unusual active Centaur P/2011 S1(Gibbs)

Abstract

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 $g_{P1}-r_{P1}=0.5\pm 0.02$, $r_{P1}-i_{P1}=0.12\pm 0.02$ and $i_{P1}-z_{P1}=0.46\pm 0.03$. The comet remained active from 2010 to 2012, with a model-dependent mass-loss rate of $\sim 100$ 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 $\sim 40$ 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.

30 pages, 6 figures, Accepted to AJ

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• The Active Centaurs
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• Outburst activity in comets: II. A multi-band photometric monitoring of comet 29p/Schwassmann-Wachmann 1
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Cited by in corpus (5)

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• Photometry of active Centaurs: Colors of dormant active Centaur nuclei
• Evolution of pits at the surface of 67P/Churyumov-Gerasimenko