Detection of Nongravitational Accelerations on Comet 133P/Elst-Pizarro

Details Detection of Nongravitational Accelerations on Comet 133P/Elst-Pizarro Detection of Nongravitational Accelerations on Comet 133P/Elst-Pizarro

Oct 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dps....42.0507c&link_type=abstract

American Astronomical Society, DPS meeting #42, #5.07; Bulletin of the American Astronomical Society, Vol. 42, p.950

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Comet 133P/Elst-Pizarro is the best observed of the main belt comets, with astrometric measurements now spanning more than 30 years and for this reason is so far the only main belt comet confirmed to have recurring periods of activity. Here we report the detection and measurement of nongravitational accelerations acting on the nucleus of Elst-Pizarro.
Using the so-called g(r) formalism of Marsden et al. [1] we estimate the radial and normal nongravitational parameters of Elst-Pizarro as, respectively, A1=12.6±4.1 and A3=7.5±6.3 in units of 10-10 AU/d2. Stated uncertainties are formal. The observational data do not reveal statistically significant transverse accelerations (i.e., A2). The statistical significance of the out-of-plane acceleration is poor, and should be interpreted merely as an indication that the accelerations are likely positive, suggesting a possible predominance of southern hemisphere activity in the case of direct rotation. On the other hand, the 3-sigma significance of the radial acceleration gives good confidence in the estimate, and indeed the estimated value of A1 is stable across a range of fit spans and data treatments.
The above parameters imply a peak acceleration of 2.5×10-10 m/s2 at perihelion. Assuming reasonable values for nucleus mass and gas velocity leads to a mass flow rate roughly of order 10 kg/s. However, the applicability of the Marsden et al. model is dubious in this case where there is good evidence that the out-gassing is governed primarily by seasonal factors rather than the simple g(r) function [2]. Thus the out-gassing could be considerably more spread in time and have a lower maximum, especially if it takes place far from perihelion. The utility of alternate out-gassing models will be considered.
Refs: [1] Marsden et al., AJ 78, 211--225, 1973. [2] Hsieh et al., AJ 127, 2997--3017, 2004.

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