Pluto’s Crazy Kerberos / New Horizons Speeds Toward New Target

This composite image shows a sliver of Pluto’s large moon, Charon, and all four of Pluto’s small moons, as resolved by the Long Range Reconnaissance Imager (LORRI) on the New Horizons spacecraft. All the moons are displayed with a common intensity stretch and spatial scale (see scale bar). Charon is by far the largest of Pluto’s moons, with a diameter of 751 miles (1,212 kilometers). Nix and Hydra have comparable sizes, approximately 25 miles (40 kilometers) across in their longest dimension above. Kerberos and Styx are much smaller and have comparable sizes, roughly 6-7 miles (10-12 kilometers) across in their longest dimension. All four small moons have highly elongated shapes, a characteristic thought to be typical of small bodies in the Kuiper Belt. Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
This composite “portrait” shows a sliver of Pluto’s large moon, Charon, and all four of Pluto’s small moons as seen by New Horizons. All the moons are to scale. Charon is by far the largest with a diameter of 751 miles. Nix and Hydra have comparable sizes, about 25 miles (40 km) across in their longest dimension above. Kerberos and Styx are much smaller and have comparable sizes, roughly 6-7 miles (10-12 km) across. All four small moons have highly elongated shapes, a characteristic thought to be typical of small bodies in the Kuiper Belt.
Credit: NASA/JHUAPL/Southwest Research Institute

Just look at ’em. Too cute. Photos of Pluto’s tiny moon Kerberos were just sent back this week from New Horizons probe, prompting NASA to create a sibling portrait. They range in size from the comparatively huge Charon at 751 miles (1,212 km) to tiny Styx and Kerberos, roughly 6-7 miles (10-12 km) across their longest dimension.

This image of Kerberos was created by combining four individual Long Range Reconnaissance Imager (LORRI) pictures taken on July 14, 2015, approximately seven hours before New Horizons' closest approach to Pluto, at a range of 245,600 miles (396,100 km) from Kerberos. The image was deconvolved to recover the highest possible spatial resolution and oversampled by a factor of eight to reduce pixilation effects. Kerberos appears to have a double-lobed shape, approximately 7.4 miles (12 kilometers) across in its long dimension and 2.8 miles (4.5 kilometers) in its shortest dimension.
This image of Kerberos was created by combining four individual pictures taken on July 14, 2015, approximately seven hours before New Horizons’ closest approach to Pluto, at a range of 245,600 miles (396,100 km) from Kerberos.The moon appears to have a double-lobed shape, approximately 7.4 miles (12 km) across in its long dimension and 2.8 miles (4.5 km) in its shortest dimension. Credit: NASA/JHUAPL/Southwest Research Institute

Kerberos surprised. It turned out to be smaller than scientists expected and has a highly-reflective surface, counter to predictions prior to the Pluto flyby in July. The tiny moon also has a double-lobed shaped that may have resulted from the merger of two separate, smaller moonlets or asteroids. The reflectivity of Kerberos’s surface is similar to that of Pluto’s other small moons — about 50% which is 20% brighter than Earth — and strongly suggests Kerberos, like the others, is coated with relatively clean water ice.

Before New Horizons’ encounter, astronomers had used the Hubble Space Telescope to attempt to weigh Kerberos based on its gravitational effects on neighboring moons. Because it appeared to have a significant tug, they naturally assumed it must be relatively large and massive. But now we see that’s it really quite small. Why remains a mystery.

Artist’s impression of NASA’s New Horizons spacecraft encountering a Pluto-like object in the distant Kuiper Belt. (Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Steve Gribben)
Artist’s impression of NASA’s New Horizons spacecraft during a potential encounter with 2014 MU69 in the Kuiper Belt in 2019. Credit: NASA/JHUAPL/Southwest Research Institute/Steve Gribben

Meanwhile, New Horizons forges toward its next potential target, the 28-mile-wide (45 km) 2014 MU69, located in the Kuiper Belt, a region beyond Neptune’s orbit home to a legion of icy asteroids. Although this new, post-Pluto mission still awaits approval, the spacecraft has carried out the second in a series of four maneuvers propelling it toward the encounter. The third maneuvers was expected today with the final on Nov. 4th. MU69 orbits a billion miles farther from the sun than Pluto..

Projected path of NASA’s New Horizons spacecraft toward 2014 MU69, which orbits in the Kuiper Belt about 1 billion miles beyond Pluto. Planets are shown in their positions on Jan. 1, 2019, when New Horizons is projected to reach the small Kuiper Belt object. NASA must approve an extended mission for New Horizons to study MU69.
Projected path of NASA’s New Horizons spacecraft toward 2014 MU69, which orbits in the Kuiper Belt about 1 billion miles beyond Pluto. Planets are shown in their positions on Jan. 1, 2019, when New Horizons is projected to reach the small Kuiper Belt object. Credit: NASA

The New Horizons team will submit a formal proposal to NASA for the extended mission in early 2016. Scientists hope to bring the spacecraft closer to MU69 than it came to Pluto back in July during a close flyby encounter with MU69 on Jan. 1, 2019.

Today, New Horizons is cruising along at more than 32,000 miles per hour. It’s now about 76 million miles (122 million km) beyond Pluto and 3.16 billion miles (5.09 billion km) from Earth. All systems are healthy and the spacecraft continues to transmit data stored on its digital recorders from the July flyby.