The Pluto stellar occultation of 18 July 2012

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On 18 July 2012 around 04:13 UT, a star in the Sagittarius constellation was occulted by the dwarf planet Pluto. The event was attempted from various sites in South America:

It was successfully monitored from various sites in Chile, Argentina and Peru. It was in particular observed at the Cerro Paranal facility of the European Southern Observatory in Chile, with the 8.2-m Very Large Telescope Yepun, using the infrared NACO camera in H band (1.65 μm), in which star was about five times brighter than Pluto.

The event was observed by Julien Girard during a ToO (Target of Opportunity) triggered as part of run ESO 089.C-0314(C)

The proximity of the dwarf planet to zenith at Paranal, photometric conditions and excellent seeing (about 0.5 arcscec in H band) allowed us to record a high signal to noise Pluto occultation event.

The panels below show 12x5.4 arcsec fields of view around Pluto. The lower panel shows an image using daptive optics, but Charon is also easily resolved even without adaptive optics (upper panel):

The cartoon below shows successive images of Pluto and the occulted star before, during and after the event:

The movie below shows a fast replay of the event at VLT, the duration of that replay corresponding to a real time interval about 2 minutes and 40 seconds:

The stellar occultation by Pluto, 18 July 2012
8.2-m Very Large Telescope/NACO/H band
European Southern Observatory, Cerro Paranal,
the movie

12x5.4 arcsec field of view. Author: Bruno Sicardy

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