Occultation Research


We use the method of stellar occultation—an object passing in front of a distant star—to observe objects in the outer solar system, starting with a search for Neptune’s rings in 1983, continuing with Neptune’s moon Triton in 1997, and then a substantial series of observations of Pluto and beyond starting in 2002. By studying the data we obtain during an occultation, we are able to determine the size and probe the atmosphere of these distant objects, gaining insight into their atmosphere’s temperature, density, chemical composition, structure, and other fascinating aspects. To image the events, we use a camera system called POETS (Portable Occultation, Eclipse, and Transit System). More information about POETS and the objects that we study can be found in subsequent pages of this website. More technical information can be found on MIT’s website on occultations: http://occult.mit.edu

This occultation work started in collaboration with the late Prof. James Elliot of MIT and his team, especially Dr. Michael Person, Dr. Amanda Bosh, and Dr. Amanda Sickafoose; the MIT-Williams Consortium keeps in close communication. At Williams, the team includes Prof. Jay M. Pasachoff and his students. It formerly also included Dr. Bryce Babcock and Dr. Steven P. Souza. Pasachoff also collaborated with Prof. Michael Brown of Caltech on studies of the dwarf planet Haumea.

Students who have participated and been or will be co-authors on published papers include:

  • Neptune (Indonesia): Steven Platt ’83
  • Triton (Australia and Hawaii): Timothy McConnochie ’98
  • Pluto (US Hawaii): David Ticehurst ’04
  • Charon (Chile) and Pluto (Australia): Joseph Gangestad ’06
  • Pluto (Australia): Anne Jaskot ’08
  • Pluto (US Southwest): Adam McKay ’08
  • Kuiper belt object 55636 (US Hawaii): Katherine DuPré ’10
  • Pluto (Chile): Muzhou Lu ’13 and Craig Malamut (KNAC ’12)
  • Pluto (US Hawaii): Shubhanga Pandey ’13 and David Amrhein (KNAC ’12)
  • Pluto (New Zealand and US computer work, 2014): Adam Schiff (KNAC ’15) and Tina Seeger ’16
  • Pluto (New Zealand and US computer work): Rebecca Durst ’17 and Tina Seeger ’16
  • Jay Pasachoff’s outreach about the 29 June 2015 occultation by Pluto see more
  • Triton occultation 2017: Ross Yu ’19, Tim Nagle-McNaughton ’18, Cielo Perez ’19 and Brendan Rosseau ’19 at Williams; Jay Pasachoff, Christian Lockwood, Allen Davis ’14 at 1-m Embry-Riddle telescope at Daytona; Mike Person (MIT) with the 2.5-m on SOFIA
  • 2014 MU69 = Ultima Thule (New Horizons’ Next Target, 1 January 2019): from Argentina, JMP with Muzhou Lu ’13
view of sky
Credit: Jack Jewell/NASA MU69 expedition to Argentina

Occultation research at Williams was supported by NASA Planetary Astronomy Research grant NNX12AJ29G. It was the latest successor to NNX08AO50G and NNH04ZSS001N.