The smallest member of the “Pluto family” has finally been captured in an image, as pictures of the tiny, two-lobed natural satellite taken by the New Horizons during the spacecraft’s July flyby of the system have been beamed back to Earth, NASA officials announced Thursday.
According to Mashable and BBC News reports, the moon known as Kerberos is actually smaller than scientists had expected, and appears to have two lobes, which may be due to two icy objects colliding with one another and merging. The larger of the lobes is approximately about five miles (eight kilometers) wide, while the other is about three miles (five kilometers) across.
Kerberos also has a surface reflectivity comparable to that of Pluto’s other smaller moons, which suggests that like the others, it has a coating of fairly clean water ice, the US space agency noted. Both discoveries came as a surprise to New Horizons scientists, who prior to July’s approach had predicted that the tiny moon would be larger, darker and more massive than it turned out to be.
“Once again, the Pluto system has surprised us,” Hal Weaver, a missions scientist from the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said in a press release. His colleague, Mark Showalter of California’s SETI Institute, added that the team’s predictions were “nearly spot-on for the other small moons, but not for Kerberos.”
Scientists unsure why Kerberos is smaller than anticipated
Prior to the probe’s close encounter with the dwarf planet and his moons, NASA researchers had used images from the Hubble Space Telescope to “weigh” Kerberos by measuring the amount of gravitational influence it had on its neighboring satellites. The strength of that influence given its relative faintness led them to theorize that the moon was relatively large and massive.
As it turns out, those predictions turned out to be wrong, for reasons not yet fully understood, the agency said. Kerberos is comparable in size to Styx and smaller than Nix and Hydra, the medium sized moons (each some 25 miles across) orbiting the dwarf planet. Additional information yet to be sent back to Earth from New Horizons may help explain why the predictions were so off.
Kerberos is the second-outermost of Pluto’s five moons, and at a distance of 60,000 kilometers from the dwarf planet, it is located between Nix and Hydra and beyond the orbits of Charon and Styx, according to BBC News. The newly released photograph of the tiny moon was captured by New Horizons’ LORRI instrument from a distance of just under 400,000 kilometers.
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Image credit: NASA
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