For decades, far-off Pluto and its moons were just a collection of bright spots in even our most powerful telescopes. Now the dwarf planet and its family of five moons has been revealed in intimate detail with the long-awaited flyby of the New Horizons spacecraft.
This week, the "family portrait" of the Pluto system was made complete with a close-up view of Kerberos, a tiny moon that wasn't even known about until 2011.
The image above was made from four separate images acquired by New Horizons' Long Range Reconnaissance Imager (LORRI) instrument several hours before the spacecraft's flyby on July 14, 2015, when it passed Pluto at a distance of only 7,800 miles (12,500 km) – less than the diameter of the Earth.
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Named after the three-headed dog that guarded the gate of the underworld in ancient Greek mythology, Kerberos the moon doesn't have three heads but it does clearly have two lobes, not unlike Rosetta's comet 67P/Churyumov-Gerasimenko. It's thought that Kerberos, like 67P, is a contact binary formed from the joining of two smaller objects.
Kerberos is about 7.4 miles (12 km) wide at its longest and is likely coated with water ice.
What's especially curious to scientists is that Kerberos, based on first observations with the Hubble Space Telescope, was thought to be relatively dark but massive compared to Pluto's other small moons. The data acquired by New Horizons have revealed that the opposite is the case.
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"Our predictions were nearly spot-on for the other small moons, but not for Kerberos," said New Horizons co-investigator Mark Showalter of the SETI Institute, who led the Hubble campaign that discovered Kerberos.
High-resolution data continues to arrive on Earth even as the New Horizons travels farther and farther away from the dwarf planet. When it is received and analyzed, it will help scientists further piece together the complex interactions between Pluto and its moons.
Find more news and images from the New Horizons mission here.