University of Virginia, College and Graduate School of Arts and Sciences

UVA Students, Faculty, and Staff Chase Shadow of Kuiper Belt Object Across South Africa

June 8, 2017

Three UVA undergraduates along with Astronomy faculty and staff mentors have returned from South Africa, data in hand, after an attempt to place three UVA telescopes in the path of the shadow of the faint distant Kuiper Belt Object 2014 MU69 as it passed in front of a distant star. This Kuiper Belt object is the target of a January 1, 2019 flyby by the New Horizons spacecraft, which encountered Pluto in the summer of 2015. UVA Astronomers Mike Skrutskie and Matt Nelson led the development of three fast and precisely timed telescope imaging systems and recruited and trained several UVA undergraduates in the art of being in exactly the right place at exactly the right time with a telescope and electronic camera pointed in exactly the right direction.

UVA's contribution was a modest part of a much larger effort involving 22 additional telescopes, 10 more in South Africa and 12 in Argentina, directed by the NASA New Horizons team with lead investigators at Southwest Research Institute in Boulder, CO. Dr. Anne Verbiscer, also with UVA Astronomy, managed the 13 South African observing teams comprising 28 people, dealing with every eventuality from fitting large telescope crates into not quite large enough trucks, to security for all of the observing teams, to ultimately making sure the teams identified "friendly" observing sites in exactly the right locations, interacting with  the U.S. Embassy in Pretoria, the U.S. Consulate in Cape Town, among others the South African Astronomical Observatory.

After three nights of telescope setup and practice, the UVa teams ended up driving inland more than 300 miles to avoid potentially bad weather on the west coast. They were rewarded with clear skies, light winds, and terrific atmospheric stability, just the right conditions to squeeze every bit of precious sensitivity out of the observing systems. All three UVA telescopes recorded optimal data during the 45 minute observing window, and especially the 5 or so seconds(!) when the object itself was predicted to pass in front of the star. Of the 25 telescope dragnet set up for this event only one or two would catch MU69's shadow as the object is estimated to be only between 15 and 30 miles across and the telescopes had to be spread over a 200 mile range to account for the uncertainty in the predictions. Data are now under analysis and it will be some time before we know just who caught the shadow. Catching it provides critical information for New Horizons as the observation will pin down the position and size of this distant object that is so faint that it has not been previously detected from the ground and appears only as a dim dot in sensitive Hubble Space Telescope images.

Read more about the expedition in Sky and Telescope.