New Horizons’ next target: spotted

NASA successfully observed the Kuiper Belt object 2014 MU69 as it passed in front of a star — for two seconds.
By | Published: July 25, 2017 | Last updated on May 18, 2023
What will New Horizons see when it reaches the Kuiper Belt object 2014 MU69? This artist’s concept imagines one possible scenario.
Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)
NASA’s New Horizons spacecraft changed our view of the outer solar system forever when it flew by Pluto in 2015. Now, it’s on its way to the next destination: a Kuiper Belt object (KBO) known only as 2014 MU69. Although the spacecraft won’t reach its target until New Year’s Day in 2019, NASA is already looking ahead to learn as much about 2014 MU69 as possible, thanks to a convenient temporary alignment that recently allowed the object to pass in front of a background star.

The passage, called an occultation, occurs when objects “line up” in the sky as viewed from Earth. When an object, such as an asteroid, planet, dwarf planet, or KBO, passes in front of a distant star, astronomers can watch the way the starlight dims and returns to gain information about the object passing in front of it. This information can include size, shape, and even whether the object possesses rings, moons, or an atmosphere.

The recent occultation was visible from the Southern Hemisphere; the New Horizons team used 24 mobile telescopes in Argentina to view the event, which lasted only about two seconds. This effort, which thus far has yielded five successful occultation detections, is vital to the characterization of 2014 MU69 before New Horizons arrives. That’s because this tiny, distant object is poorly understood; currently, it’s believed to span about 14-25 miles in diameter (22-40 kilometers), but little else is known about its shape and composition — thus far.

As 2014 MU69 passed in front of a distant star as seen from Earth, the star’s light winked out. The time difference between each frame in this image is 0.2 seconds.
Now, armed with the data from this occultation and two additional recent occultations (June 3 and July 10), the New Horizons team will get to work to better understand the spacecraft’s next stop.

“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!” said Alan Stern, the New Horizons mission principal investigator, in a press release. “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. Thanks to this success we can now plan the upcoming flyby with much more confidence.”

Currently, New Horizons is 38 astronomical units (AU; 3.5 billion miles [6 billion km]) from Earth and just over 4 AU (400 million miles [600 million km]) from 2014 MU69 (which sits more than 4 billion miles (6.5 billion km) from our planet. It’s zipping along at nearly 9 miles per second (14 km/s). At its current location, it takes light — and radio signals — a little over 5 hours and 15 minutes to travel one way between Earth from the spacecraft, and vice versa. However, the spacecraft is currently in the midst of a 157-day “hibernation,” which began in April.