Pluto Occultation — A First Report

By: The Editors of Sky & Telescope March 26, 2007 0

Amateur astronomer Chris Peterson recorded the March 18th Pluto occultation with a 12-inch telescope and CCD camera at his Cloudbait Observatory in Guffey, Colorado. In the time before and after the occultation the planet and star could not be resolved, and appeared as a single starlike object (indicated by tick marks) in the view above.

Chris Peterson

Professional and amateur astronomers are continuing to sift through and analyze data they collected during the March 18th occultation involving Pluto and a 15th-magnitude star in Sagittarius. It was the best-ever Pluto occultation predicted for North America, and according to occultation expert David Dunham, the event was successfully recorded at more than 20 locations in the central and western United States.

Preliminary analysis of the data by Bruno Sicardy of Paris Observatory, who observed with the 2.3-meter Bok Telescope in Arizona, indicate that the occultation occurred about 4.8 minutes later than predicted, and that the occultation track was somewhat north of predictions.

Amateur astronomer Chris Peterson recorded the March 18th Pluto occultation with a 12-inch telescope and CCD camera at his Cloudbait Observatory in Guffey, Colorado. During the roughly five minutes that it took for Pluto and it's atmosphere to pass in front of the 15th-magnitude star, the total light from the pair dropped by nearly ½ magnitude.

Chris Peterson

As such, observers in the southern portion of the track that crossed Arizona and Texas witnessed a gradual drop in the combined light of Pluto and the star followed immediately by a gradual increase in brightness. This is indicative of an occultation by Pluto's atmosphere, but not by the planet's solid surface, which would have caused a flat-bottomed light curve during the time the star was completely hidden behind the planet.

Dunham's website has a summary of the occultation observations, including links to results obtained at a number observatories, both amateur and professional.