Spaceflight Insider

Occultation data hints New Horizons’ next flyby target may have a moon

New Horizons / KBO 2014 MU69 encounter

Artist’s rendition of New Horizons’ forthcoming flyby of Kuiper Belt Object 2014 MU69. Image Credit: NASA / JHU-APL / SwRI

New Horizons‘ second target – Kuiper Belt Object (KBO) 2014 MU69 – may have a small moon, mission science team member Marc Buie of the Southwest Research Institute (SwRI) in Boulder, Colorado, reported on Monday, December 11, 2017, at this week’s meeting of the American Geophysical Union (AGU) in New Orleans, Louisiana.

Mission scientists learned a lot about the KBO when it occulted (or passed in front of) three separate stars this past summer.

For the first and third occultation, they set up a network of telescopes within the narrow path of the shadow cast by the KBO as it passed in front of each star, which enabled them to measure MU69’s orbit, size, and shape.

They observed the second occultation with NASA’s airborne Strategic Observatory for Infrared Astronomy (SOFIA) while flying over the Pacific Ocean on July 10, 2017.

As the scientists targeted MU69’s expected location from their airborne observatory, they observed a brief drop off or “blip” in the light of the star being obscured by the KBO.

When they later analyzed data collected during the observation and matched it with calculations of MU69’s orbit done by the European Space Agency’s (ESA) Gaia observatory, mission scientists determined the “blip” could have been caused by a small satellite orbiting the KBO.

Some scientists have theorized that MU69 could be a swarm of objects rather than a single one or a binary.

On three occasions in June and July 2017, New Horizons mission team members attempted to track a small, distant Kuiper Belt object, 2014 MU69, as it passed in front of a star – an event known as an occultation. The colored lines mark the path of the star as seen from different telescopes on each day; the blank spaces on those lines indicate the few seconds when MU69 blocked the light from the star. Scientists are using these observations to craft a picture of MU69 and any companion bodies. (Click on either image to enlarge) Images & Caption Credit: NASA / JHU-APL / SwRI / James Tuttle Keane

Successful observations of the final July 17 occultation with five telescopes placed along the shadow path in Argentina revealed MU69 might be a double-lobed object or a binary system of two objects closely orbiting each other.

New Horizons in space

Artist’s rendition of NASA’s New Horizons spacecraft in space. Image Credit: NASA / JHU-APL / SwRI

“A binary with a smaller moon might help explain the shifts we see in the position of MU69 during these various occultations,” Buie noted. “It’s all suggestive, but another step in our work to get a clear picture of MU69 before New Horizons flies by, just over a year from now.”

The flyby will take place on New Year’s Eve and New Year’s Day 2019, with the closest approach at 12:33 a.m. EST (5:33 GMT) on January 1, 2019.

Discovered with the Hubble Space Telescope by mission scientists in 2014 during a search while searching for a second New Horizons target after Pluto, MU69 is estimated to have a diameter of about 20 miles (30 km). If it is a binary system, each object likely has a diameter ranging between nine and twelve miles (15–20 km).

Located more than four billion miles (6.5 billion km) from Earth, MU69, which could become the most distant object ever visited by a spacecraft, is composed of pristine materials that are leftovers from the process of planet formation in the early solar system more than four billion years ago.

Buie pointed out that the KBO becomes more interesting each time it is studied from afar.

“We really won’t know what MU69 looks like until we fly past it, or even gain a full understanding of it until after the encounter,” he emphasized.

Successful observations of last summer’s occultations have revealed MU69 to be more complex than previously thought, said Principal Investigator Alan Stern, who thanked Buie and his team for the “invaluable” data collected during last summer’s observations.



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.

Reader Comments

Seems strange that NASA could find a new target for New Horizons, but not for Pioneer or Voyager. Didn’t anyone think about it, or we’re there no targets available on their current trajectory?

The Timelines dont line up for that. Kuiper Belt Objects are a relatively new discovery, having first been found in 1992, after a 5 year search. The other probes passed their last target long before (pioneer 10 – ’73, pioneer 11 – ’79, voyager 1 – ’80 – voyager 2 -’89).

The geometry prevented any redirects after the discovery of the Kuiper Belt. The main crux of the belt extends roughly 10degrees from the ecliptic plane. After passing Neptune, Voyager 1 was kicked 35deg north, and Voyager 2 is angled about 50deg south. Given those large angles traveled along for 10yrs, small thrusters (fuel capacity), and their velocities, it just isn’t possible. Pioneer 11 got kicked out of plane 15deg if I recall. Pioneer 10 pass through the region, but by the mid 90s communication was very faint, and getting harder to keep.

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