Spaceflight Insider

Stellar occultations by KBO 2014 MU69 will give scientists crucial data

Artist's impression of NASA's New Horizons probe encountering the distant Kuiper Belt Object 2014 MU69

Artist’s impression of NASA’s New Horizons spacecraft encountering the distant Kuiper Belt Object 2014 MU69. Image Credit: NASA / JHU-APL / SwRI / Steve Gribben

Members of NASA’s New Horizons team will have three opportunities to obtain crucial data regarding 2014 MU69 – the mission’s second target – when the Kuiper Belt Object (KBO) occults three different stars within the next few weeks.

Located more than four billion miles (6.44 billion kilometers) from Earth, about a billion miles (1.6 billion kilometers) beyond Pluto, 2014 MU69 will occult, or pass directly in front of, three different stars within the next few weeks on June 3, July 10, and July 17.*

2014 MU69 occultation shadow path – 2017-06-03

First look: Projected path of the 2014 MU69 occultation shadow, across South America and the southern tip of Africa, on June 3. Image & Caption Credit: Larry Wasserman / Lowell Observatory / JHU-APL

Although the small KBO will block each of the stars’ light for (at most) two seconds, observing the event will provide mission scientists with an unprecedented opportunity to obtain crucial data about it, including its size, shape, orbit, and reflectivity.

Little is known about 2014 MU69 – including its orbit – because it was discovered just three years ago during a search for a second New Horizons flyby target.

New Horizons mission scientists and engineers had nearly seven years to plan for the 2015 Pluto encounter, but they will have, at most, two years to plan this one – scheduled for January 1, 2019.

“We were only able to start planning the MU69 encounter after we flew by Pluto in 2015,” said Carly Howett of the Southwest Research Institute (SwRI), deputy principal investigator of the spacecraft’s Ralph instrument. “That gives us two years, instead of almost seven years we had to plan the Pluto encounter. So it’s a very different, and in many ways, more challenging flyby to plan.”

Adding to the difficulty is the fact that so little is known about the target object.

To take advantage of the opportunities provided by the occultations, scientists are setting up both portable and stationary telescopes along the projected paths of 2014 MU69‘s shadow.

Over 50 scientists plan to observe the June 3 occultation from areas along the path in Argentina and South Africa by turning telescopes equipped with cameras at multiple locations.

A total of 22 16-inch (40-centimeter) portable telescopes and more than 24 fixed location telescopes will be spaced every six to 18 miles (10 to 25 km) along the shadow’s most likely path across the Earth to maximize the chances of one or more successful observations.

2014 MU69 occultation telescope preperation

New Horizons team members prepare one of the new 16-inch telescopes for deployment to occultation observation sites in Argentina and South Africa. Photo & Caption Credit: Kerri Beisser / JHU-APL

Ideally, the various telescopes will see different portions of the shadow, providing data that will enable scientists to determine the KBO’s brightness and shape.

The telescopes will also search for potentially harmful debris particles that could seriously damage or destroy New Horizons as it speeds by 2014 MU69 at 35,000 miles (56,000 kilometers) per hour.

“Our primary objective is to determine if there are hazards near MU69 – rings, dust, or even satellites – that could affect our flight planning,” said Principal Investigator Alan Stern of SwRI. “But we also expect to learn more about its orbit and possibly determine its size and shape. All of that will help our flyby planning effort.”

Similar searches for potential hazards were conducted by mission scientists in advance of the Pluto flyby.

“Deploying on two different continents also maximizes our chances of having good weather,” said deputy project scientist Cathy Olkin, also of SwRI. “The shadow is projected to go across both locations and we want observers at both, because we wouldn’t want a huge storm to come through and cloud us out – the event is too important and too fleeting to miss.”

Mission members’ best chance to observe 2014 MU69 will come on July 10 when they will have access to NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) airborne observatory, which is equipped with a 100-inch (2.5-meter) telescope.

Flying above the clouds, SOFIA will not be subject to weather and will be capable of maneuvering into the center of the KBO’s shadow.

Knowing the object’s size and reflectivity will help scientists and engineers calculate the best exposure times for cameras and spectrometers during the flyby.


*Updated at 18:10 EDT, May 29, 2017, with links to information.



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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