| Summary: | International audience The imminent return of comet 8P/Tuttle is expected to cause Ursid shower outbursts on December 22. There are occasional visual and forward meteor scatter observations of such outbursts from the previous perihelion return of 1994, and the one before that in 1980. In this paper, we investigated what may cause these outbursts and make predictions on what to expect from dust trails ejected in the period AD 300 - 1400. Younger trails do not contribute to these Filament-type outbursts. Our knowledge of the position of older trails suffers progressively from an uncertain position of the comet in its orbit. The comet passed close to Jupiter's orbit 15 000 years ago, at which time it may have been captured. We find that Jupiter's influence at the ascending node causes some meteoroids to evolve into resonant orbits that move into Earth's path. For 2007, we expect a strong shower with a peak ZHR = 40 - 80 per hour and a duration of FWHM = 2 - 8.5 hours, centered on December 22 at 20.0 h - 22.2 h UT (most likely 21.4 h - 22.2 h UT). Peak rates in 2008 - 2012 will be less. The exact peak time and duration, as well as structure in the shower profile, can identify the age of the stream. To find out, an airborne observing campaign is being prepared that would deploy from NASA Ames Research Center in California and would observe the 2007 December 22 Ursid shower over the Canadian arctic.
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