Pluto's near miss still provides useful information

  • Published
  • By Jeanne Dailey
  • Air Force Research Laboratory
KIRTLAND AIR FORCE BASE, N.M. --  Pluto was recently of special interest to some scientists because it was expected to occult, or overlap, a star, providing information on Pluto's atmosphere.

This occultation would be visible on Earth only in the Hawaiian Islands, so the Southwest Research Institute in Boulder, Colo., asked Dr. Keith Knox, Air Force Research Laboratory's Directed Energy Directorate scientist at the Air Force Maui Optical and Supercomputing site, to participate in a collection of photos of the event.

AFRL had the telescope for the job - the Advanced Electro-Optics System, or AEOS, a 3.6-meter telescope which is largest telescope in the Department of Defense.

The occultation of a dim star by Pluto was predicted to be visible in Hawaii on June 29, 2012. AFRL researchers arose at 1 a.m. at their 10,000-foot observatory location, on the extinct volcano Haleakala, to begin collecting data. The AEOS telescope collected imagery 50 minutes before and after the expected time of occultation at the rate of 5 frames per second, for a total of 30,000 frames.

Unfortunately, analysis showed Pluto had missed the star.

"Our analysis of the data shows that Pluto missed the star by only 0.135 arc sec, which is slightly greater than the diameter of Pluto itself," Knox said. "The center of the mass of Pluto and its largest moon, Charon, passed almost directly over the occultation star, but the orientation of Pluto and Charon was such that they passed on either side of the star and neither body blocked its light. As a result, no information about the atmospheres of either Pluto or Charon was obtained."

Knox said despite Pluto not occulting the star, they were still interested in the event.

"Our analysis of why and by how much Pluto missed occulting the star will aid us in predicting the motions of other objects in space," he said. "Our goal is to understand the orbits of all objects in space well enough to prevent damage to valuable satellites through accidental collisions with debris."