New Horizons scientists successfully observe second target during stellar occultation

The New Horizons team used a new technique to guide the spacecraft to its next target. Image credit: NASA

New Horizons scientists observed on August 4, 2018 the second target of the spacecraft, Ultima Thule, when the object of the Kuiper Belt (KBO) passed in front of an obscured star.

Despite climatic conditions, such as the occultation that occurred at the beginning of the rainy season in Senegal, the observation was even more fruitful than three observations of occultation during the summer 2017, providing information on the shape and size of Ultima Thule. According to a mission statement, nearby hazards, such as dark circles or debris.

Marc Buie, manager of the occultation team, at the center, discovers the detection of Ultima Thule by stellar occultation in Louga, Senegal, with Maram Kaire, technical advisor at the Ministry of Energy. Higher Education, Research and Innovation or MESRI in Senegal. David Baratoux, left, director, African Initiative for Planetary and Spatial Sciences; Research Institute for Development, University of Toulouse, France. Photo and legend Credit: NASA / Johns Hopkins University Applied Physics Laboratory / South West Research Institute / Anne J. Verbiscer

NASA's Hubble Space Telescope (HST) has observed the occultation from space, as was the case last year, specifically to search for rings and other potential hazards for the spacecraft. The telescope was better positioned this time and could see nearly 1600 kilometers of Ultima Thule.

Last year, Hubble was closest at about 12,000 miles because it was positioned on the opposite side of the Earth in the middle of the occultations.

Josh Kammer, a member of the Southwest Research Institute (SwRI) observation team in Boulder, Colorado, found no trace of rings around Ultima Thule.

"There were no detectable ring signatures for one or the other event, so by using Hubble data, we were able to set important constraints on the Presence of rings or dusts that could compromise a secure flyby, "said Kammer.

Marc Buie, also of SwRI Boulder, led the observation team, which received international support, including assistance from Senegal, Colombia, Mexico and France.

"We owe much of the success of these observations to this incredible multinational collaboration," said Buie. "This work is in preparation for our next New Horizons flyby, which will take place on January 1st, during which we hope to learn much more about Ultima Thule by taking a closer look."

Anne Verbiscer, scientific assistant for the New Horizons project at the University of Virginia, praised the Senegalese colleagues on the team, whose efforts contributed to the project's success.

The occultation data, as well as the navigation tracking, help the New Horizons team to formulate commands that will be uploaded to the spacecraft in anticipation of the flyby. Scientific instruments and subsystems will be verified for the event, and a course correction to Ultima Thule will be made in early October.

Placed more than one billion kilometers beyond Pluto, Ultima Thule and small KBOs like this one are made of immaculate materials from the earliest stages of the solar system and can provide scientists with insight into the formation of planets and of the third zone of the solar system.

Occultation data from last year indicates that Ultima Thule is either a double lobe object or a binary system consisting of two objects in orbit. It could also be a binary contact, in which the two objects in orbit actually touch each other. There is also evidence that Ultima Thule could have a moon.

François Colas, from Paris Observatory, and Salma Sylla Mbaye, left, from Cheikh Anta Diop University in Dakar, Senegal, show their telescope to Mary Teuw Niane, center right, Senegalese Minister of Education, Research and Innovation or MESRI, at one of the practice sessions held near Dakar before stellar occultation of Ultima Thule, while other visitors (left) look on. Photo and caption Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute / Mike Grusin

Tagged: New Horizons occultation Senegal The Ultima Thule Range

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Laurel Kornfeld

Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, New Jersey, who loves writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a scientific certificate from Astronomy Online at Swinburne University. His writings have been published online in The Atlantic, the Astronomy magazine's blog section, the British Space Conference, the 2009 IAU General Assembly Journal, The Space Reporter, and bulletins from various astronomy clubs. She is a member of Amateur Astronomers, Inc. based in Cranford, New Jersey. Particularly interested in the outdoor solar system, Laurel made a short presentation at Great Planet Debate 2008 at the Applied Physics Laboratory