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M. F. A'Hearn (UMD), M. J. S. Belton (BSEI), C. J. Crockett, T. L. Farnham, L. Feaga, O. Groussin (UMD), N. Mastrodemos, W. M. Owen (JPL), J. M. Sunshine (SAIC), Deep Impact Team
The Deep Impact (DI) project provided unprecedented, intensive monitoring of comet Tempel 1 not only by the DI spacecraft, but also by numerous ground-based and Earth-orbital facilities. This led to the serendipitous discovery of frequent, small outbursts by the comet prior to impact. The initial realization of outbursts came from processed observations at Calar Alto (Lara 2005) but a combination of real-time and retrospective analysis of data from the spacecraft showed 6 outbursts between May 15 and July 2 (A'Hearn et al 2005), one of which was also observed serendipitously by HST (Feldman, priv. comm.).
The outbursts are of very short duration (typically no more than ten minutes) and the ejecta dissipate into the background within a day in most cases. Analysis of the shape model shows that several of the outbursts occurred at a very similar rotational phase, one very close to the time of sunrise over a large, relatively flat portion of the nucleus. The spatial distribution of the ejecta is consistent with the outburst occurring from that area. Spectra taken serendipitously during one of the outbursts show features in the near-IR that are not yet identified at the time of preparing this abstract. Since the comet is very typical in many ways, it seems likely that outbursts such as these occur on many comets and analysis of these outbursts should shed light on the much larger outbursts, observed much less frequently, in other comets.
This work was funded by NASA through the Deep Impact project.
A'Hearn, M. F., et al. 2005. Science, Oct 15 issue.
Lara, L. M., et al. 2005. Astron. Astrophys., in press.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.