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New Horizons team obtains wealth of data from 2014 MU69 occultation

A 2014 MU69 occultation campaign telescope

A 2014 MU69 occultation campaign telescope. Photo Credit: NASA / JHU-APL / SwRI

NASA’s New Horizons team captured crucial data on Kuiper Belt Object (KBO) 2014 MU69 – the spacecraft’s second target – during a third organized observation of the KBO occulting a star on Monday, July 17, 2017.

Mission scientists traveled to a remote area in Argentina to catch MU69 pass in front of a star after analysis of observations made with the Hubble Space Telescope and the Gaia satellite determined the location where the KBO would cast a shadow on Earth’s surface.

Occultation of a star by KBO 2014 MU69

Now you see it, now you don’t: NASA’s New Horizons team trained mobile telescopes on an unnamed star (center) from rural Argentina on July 17, 2017. A Kuiper Belt object 4.1 billion miles from Earth – known as 2014 MU69 – briefly blocked the light from the background star, in what’s called an occultation. The time difference between frames is 200 milliseconds (0.2 seconds). This data helps scientists to better measure the shape, size, and environment around the object; the New Horizons spacecraft will fly by this ancient relic of Solar System formation on Jan. 1, 2019. Animation & Caption Credit: NASA / JHU-APL / SwRI

Led by Marc Buie of the Southwest Research Institute (SwRI), more than 60 scientists braved cold weather and high winds, setting up a line of 24 portable telescopes in Chubut and Santa Cruz, Argentina.

They received support and logistical assistance from Argentinian government officials, scientists, and members of the public, including a two-hour closure of a highway to prevent headlights from impeding the observation.

Located 4.1 billion miles (6.6 billion km) from Earth and one billion miles (1.6 billion km) beyond Pluto, MU69 blocked the light of a bright background star for just 0.2 seconds, but that was enough for at least five observation teams to capture the event.

“It was the most historic occultation on the face of the Earth,” said NASA director of planetary science Jim Green, who called the team to congratulate them. “You pulled it off and made it happen.”

Mission co-investigator Amanda Zangari was the first to detect the signature of the 14–25 miles (22–40 kilometers) wide KBO, which the spacecraft will fly by on January 1, 2019.

MU69 will then be the most distant object to be visited by a spacecraft.

The July 17 event was the last of three stellar occultations by the KBO. The other two occurred on June 3 and July 10. Mission scientists traveled to Argentina and South Africa to observe the June 3 event, then flew above the clouds in NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) aircraft over the Pacific Ocean from New Zealand for the second one in an effort to study the KBO’s environment.

That study centered on detection of any potential hazards near MU69 that could pose a threat to New Horizons.

While it will take scientists weeks to analyze all the data collected during the occultations, that data will play a key role in helping them discover its size, shape, orbit, and environment.

MU69 was detected in 2014 by the Hubble Space Telescope as part of the New Horizons’ team’s search for a second flyby target after Pluto, but it was too remote for any constraint on its size and shape.

Buie praised the Argentinian community of Comodoro Rivadavia for assisting the team by turning off street lights and even parking trucks to act as windbreakers.

“The local people were a major team player,” he emphasized. He specifically thanked Argentina’s National Commission on Space Activities and the Argentinian people for their assistance, noting the effort is an example of space exploration bringing out the best in everyone.

Principal Investigator Alan Stern said: “This effort, spanning six months, three spacecraft, 24 portable ground-based telescopes, and NASA’s SOFIA airborne observatory was the most challenging stellar occultation in the history of astronomy, but we did it. We spied the shape and size of 2014 MU69 for the first time, a Kuiper Belt scientific treasure we will explore just over 17 months from now.”

LEFT: Marc Buie, New Horizons occultation campaign lead, holds up five fingers to represent the number of mobile telescopes in Argentina initially thought to have detected the fleeting shadow of 2014 MU69. The New Horizons spacecraft will fly by the ancient Kuiper Belt object on Jan. 1, 2019. RIGHT: New Horizons Co-Investigator Amanda Zangari was the first occultation campaign scientist to see the telltale signature of MU69 while analyzing data from July 17, saying, “We nailed it spectacularly.” Credits: NASA / JHU-APL / SwRI / Adriana Ocampo


A video depicting preparations for the July 17 occultation is available for viewing here, and reports on all three occultation observations can be viewed here.



Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

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