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Imaging polarimetry of the dust coma of Comet Tempel 1 before and after Deep Impact at Haute-Provence Observatory |
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| Authors: | E Hadamcik AC Levasseur-Regourd D Bardin |
| Institution: | a Université Pierre et Marie Curie - Paris 6, UMR 7620 (SA/IPSL), BP 3, 91371 Verrières-le-Buisson, France b Université Paris 11, UMR 8617, Bat 121, 91405 Orsay, France c Andromède, Observatoire de Marseille, 2 place Le Verrier, 13248 Marseille Cedex 04, France |
| Abstract: | We have observed the coma of Comet 9P/Tempel 1, the target of the Deep Impact mission, by the polarization imaging technique, before and after the impact event (−32, −7, +43 and +65 h). Our observations were conducted in the red wavelength domain from Haute-Provence Observatory (France), with the 80-cm telescope. The overall polarization of 9P/Tempel 1, as obtained near 41° phase angle, is monitored and compared to data from other (active and less active) comets studied by the same technique. The linear polarization of the dust ejected by the impact is compared to previous observations of dust present in jets, ejected during outbursts or released when comets happen to split. At phase angles of about 41°, the difference in polarization between the comets with a low maximum in polarization and the comets with a high maximum in polarization is about 1%; it may thus be difficult to conclude about the classification. Nevertheless, the overall polarization after the impact rapidly reached a value corresponding to the high polarization class of comets, and later progressively decreased to its initial value. The polarization was measured to be slightly lower (about 1%) before the impact than after it in a 26,000-km aperture. The plume formed from dust ejected by the impact was still present 65 h after it. The variations of the intensity and the polarization in the coma provide some clues to variations of the physical properties of the particles; comparison with other techniques corroborates the presence of large particles and of submicron-sized grains in aggregates. |
| Keywords: | Comets dust Comets coma Comet Tempel-1 Impact processes Polarimetry |
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