A year ago, I wrote that Pluto had four
moons. Make that five. The
cosmologists at the SETI (Search for Extraterrestrial Intelligence) Institute
and NASA/ESA have found a fifth moon lurking in their Hubble images. They
hadn’t even gotten around to naming the fourth moon yet, which is still
designated ‘P4’. Consequently, the newest one is ‘P5’.
This image, taken by NASA's Hubble Space Telescope, shows
five moons orbiting the distant, icy dwarf planet Pluto. The green circle marks
the newly discovered moon, designated P5, as photographed by Hubble's Wide
Field Camera 3 on July 7.
Credit: NASA; ESA; M. Showalter, SETI Institute
The four newer moons (Hydra, Nix, P4 and P5) were all also discovered in images from the Hubble Space Telescope. Charon, discovered in
1978, is the only one of Pluto’s moons that a person couldn’t easily
circumnavigate on foot (especially considering that you’d be all but
weightless). P5 is estimated to have an irregular shape that ranges from about
10 to 20 kilometers in diameter.
Although it’s not clear why tiny Pluto has a cluster of
miniature moons, the leading hypothesis is that the grouping is the result of a
collision that occurred soon after the formation of the solar system. It’s
certainly possible that even more moons will be discovered in the future.
Not bad for an object that’s not even a planet.
You can hear a discussion about P5 on The Skeptics' Guide To The Universe - Podcast 366, starting at 27:30.
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