San Pedro de Atacama Celestial Explorations

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Double occultation, 134340 Pluto and Charon, June 4th 2010

Published on Saturday 11 June 2011


This is the first time a simultaneous double occultation is observed at three different sites : Pico dos Dias in Brazil, TRAPPIST telescope in La Silla, and here.

There was a double occultation of Pluto and Charon observed the 22nd of June 2008, but Charon was "above" Pluto and a given sites could not observed both occultations from the same site and same instrumentation. This occultation will not substantially change our knowledge of the diameters of Pluto or Charon, but will give a very precise measurement of the projected distance between Pluto and Charon which will help refine the orbit of Charon and help for example to predict the position of Charon compared to Pluto during the flyby of the New Horizon mission in 2015.

This is a very preliminary (quick and very dirty) light curve of the even as observed using the Harlingten 50cm telescope by myself.


One can see around image 390 the result of the occultation of Charon, a fairly square dip in magnitude (in this diagram, fainter magnitudes are up, larger magnitude, meaning fainter) and then starting at image 600 the result of the occultation of the star by Pluto, being a rather smooth, almost gaussian curve, because Pluto has an atmosphere which refracts the star behind it.

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