|
|||||
|
|
Radio observations of Comet 9P/Tempel 1 before and after Deep Impact |
|
| Authors: | Nicolas Biver Dominique Bockelée-Morvan Jacques Crovisier Alain Lecacheux Gabriel Paubert Matthew Sumner Åke Hjalmarson Anders Winnberg Aage Sandqvist |
| Institution: | a LESIA, CNRS UMR 8109, Observatoire de Paris, 5 pl. Jules Janssen, F-92190 Meudon, France b IRAM, Avd. Divina Pastora, 7, 18012 Granada, Spain c California Institute of Technology, MC 320-47, Pasadena, CA 91125, USA d Swedish Space Corporation, P.O. Box 4207, SE-17104 Solna, Sweden e Onsala Space Observatory, SE-43992 Onsala, Sweden f Stockholm Observatory, SCFAB-AlbaNova, SE-10691 Stockholm, Sweden g Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4, Canada h Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan |
| Abstract: | Comet 9P/Tempel 1 was the target of a multi-wavelength worldwide investigation in 2005. The NASA Deep Impact mission reached the comet on 4.24 July 2005, delivering a 370-kg impactor which hit the comet at 10.3 km s−1. Following this impact, a cloud of gas and dust was excavated from the comet nucleus. The comet was observed in 2005 prior to and after the impact, at 18-cm wavelength with the Nançay radio telescope, in the millimeter range with the IRAM and CSO radio telescopes, and at 557 GHz with the Odin satellite. OH observations at Nançay provided a 4-month monitoring of the outgassing of the comet from March to June, followed by the observation of H2O with Odin from June to August 2005. The peak of outgassing was found to be around  between May and July. Observations conducted with the IRAM 30-m radio telescope in May and July 2005 resulted in detections of HCN, CH3OH and H2S with classical abundances relative to water (0.12, 2.7 and 0.5%, respectively). In addition, a variation of the HCN production rate with a period of 1.73±0.10 days was observed in May 2005, consistent with the 1.7-day rotation period of the nucleus. The phase of these variations, as well as those of CN seen in July by Jehin et al. Jehin, E., Manfroid, J., Hutsemékers, D., Cochran, A.L., Arpigny, C., Jackson, W.M., Rauer, H., Schulz, R., Zucconi, J.-M., 2006. Astrophys. J. 641, L145-L148], is consistent with a rotation period of the nucleus of 1.715 days and a strong variation of the outgassing activity by a factor 3 from minimum to maximum. This also implies that the impact took place on the rising phase of the “natural” outgassing which reached its maximum ≈4 h after the impact. Post-impact observations at IRAM and CSO did not reveal a significant change of the outgassing rates and relative abundances, with the exception of CH3OH which may have been more abundant by up to one order of magnitude in the ejecta. Most other variations are linked to the intrinsic variability of the comet. The Odin satellite monitored nearly continuously the H2O line at 557 GHz during the 38 h following the impact on the 4th of July, in addition to weekly monitoring. Once the periodic variations related to the nucleus rotation are removed, a small increase of outgassing related to the impact is present, which corresponds to the release of ≈5000±2000 tons of water. Two other bursts of activity, also observed at other wavelengths, were seen on 23 June and 7 July; they correspond to even larger releases of gas. |
| Keywords: | Comets composition Comet 9P/Tempel 1 Radio observations |
| 本文献已被 ScienceDirect 等数据库收录！ | |