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Session 69 - Instabilities in Planetary Systems.
Display session, Friday, January 09
Exhibit Hall,
The gravitational impulse of close approaches of stars to the Oort comet cloud are thought to be responsible for randomizing the orientations and eccentricities of their orbits. Particularly close encounters or combinations of more distant encounters can affect the distribution of comets observed at Earth.
We present calculations of the recent encounter with Algol and the future encounter with Gliese 710. The Algol computation uses a new measurement of the proper motion made with Very Long Baseline Interferometry, which has uncertainties six times less than the Hipparcos measurements. We discuss in detail the various sources of uncertainty. We find that including the galactic rotation and oscillation about the midplane is essential to accurately compute not only the distance of closest encounter, but also which side of the Sun the stars will pass. Finally, we discuss the impact of the Algol passage on the observed distribution of comet orbits.
