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New Horizons’ second target may be different than initially thought

Four members of the South African observation team scan the sky while waiting for the start of the 2014 MU69 occultation, early on the morning of June 3, 2017. The target field is in the Milky Way, seen here from their observation site in the Karoo desert near Vosburg, South Africa. They used portable telescopes to observe the event, as MU69, a small Kuiper Belt object and the next flyby target of NASA’s New Horizons spacecraft, passed in front of a distant star. Credits: NASA/JHUAPL/SwRI/Henry Throop

Observations conducted by New Horizons scientists during the first of three stellar occultations by the spacecraft’s second target, Kuiper Belt Object (KBO) 2014 MU69, suggest the KBO may be smaller and brighter than initially thought.

On June 3, over 50 mission scientists and others assisting the effort observed MU69 pass in front of, or occult, a star from locations in South Africa and Argentina.

Together, scientists captured more than 100,000 images of the star along the track of MU69’s shadow. These images will reveal information about the KBO’s environment, and data taken during the occultation has already been helpful to mission scientists.

Although no images of MU69 itself were captured, the data collected provides new insights into its size and reflectivity.

Discovered with the Hubble Space Telescope in 2014, MU69 was estimated at the time to have a diameter between 12 and 25 miles (20-40 km).

“These data show that MU69 might not be as dark or as large as some expected,” said New Horizons science team member and occultation team leader Marc Buie of the Southwest Research Institute (SwRI) in Boulder, Colorado.

Even though the KBO itself was not imaged, the observations shed new light on MU69, according to New Horizons Principal Investigator Alan Stern, also of SwRI.

“These results are telling us something really interesting. The fact that we accomplished the occultation observations from every planned observing site but didn’t detect the object itself likely means that either MU69 is highly reflective and smaller than some expected, or it may be a binary or even a swarm of smaller bodies left from the time when the planets in our solar system formed.”

MU69 is located approximately one billion miles beyond Pluto. New Horizons will fly by the KBO on January 1, 2019.

Mission scientists will have two more chances to observe the KBO when it occults another star on July 10 and a third star on July 17.

NASA’s airborne Stratospheric Observatory for Infrared Astronomy (SOFIA) will aim its 100-inch (2.5-meter) telescope at MU69 during the July 10 occultation to search for potential hazards to the spacecraft in the region.

Hubble will observe the July 17 event, which will also be tracked by a ground-based team in southern Argentina.

Laurel Kornfeld

Laurel Kornfeld

Staff Writer
Laurel Kornfeld is a freelance writer and amateur astronomer 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 in astronomy from Swinburne University’s Astronomy Online program.
About Laurel Kornfeld (1100 Articles)
Laurel Kornfeld is a freelance writer and amateur astronomer 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 in astronomy from Swinburne University’s Astronomy Online program.