Motion of Pluto

This pair of images shows the apparent motion of Pluto over a span of 3 hours 6 minutes, as seen on 25 June 1993 from the Lowell Observatory 1.1-meter Hall telescope (I think there's some kind of peer pressure to do outer planets from Lowell, no matter your specialty). The position shift in this time amounts to 9.0 arcseconds. For outer planets, their own orbital motion is so slow that their apparent motion is usually dominated by parallax effects from the Earth's own orbit. Clyde Tombaugfh used this in weeding out the many interloping minor planets while searching for Pluto, and modern searchers for Kuiper-belt objects at greater distances use it as well - looking at opposition, straight away from the Sun, the apparent motion of an object in a fairly circular orbit is a good indx of its distance.

Each image is a 3-minute exposure through a V filter. The sections compared here are 106 by 212 arcseconds in angular extent. The separation between Pluto and Charon is about one pixel (i.e. totally invisible, if you must rub it in).

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