In a mysterious region beyond the orbit of the beautiful, banded, blue ice-giant planet Neptune–the most distant of the eight major planets from our Sun–there is a dark and frigid domain called the Kuiper Belt. Within this remote region, where our Sun shines with only a weak fire, and appears to be merely a particularly large star suspended in the black sky, a multitude of strange, icy worldlets tumble around our Star. Pluto, a large icy denizen inhabiting the Kuiper Belt, was originally classified as the ninth major planet from our Sun after its discovery in 1930. However, with the realization that this frozen “oddball” is really only one of several large, icy inhabitants of the Kuiper Belt, the International Astronomical Union (IAU) found it necessary to formally define “planet” in 2006–and poor Pluto was unceremoniously ousted from the pantheon of major planets. Pluto, now freshly reclassified as a dwarf planet, nonetheless remains a small world of great interest, debate, and affection. Scientists will soon learn much more about this beloved, distant, ice-ball so far away, when, after a treacherous nine-year journey of three million miles through interplanetary space, NASA’s hearty New Horizons spacecraft arrives at Pluto on July 14, 2015.
However, weeks before New Horizons’ scheduled arrival at its main target, it managed to reveal some strange secrets long-held in the deep freeze of our Solar System’s outer limits. For their new study, released in June 2015, a team of planetary scientists collected all available NASA and European Space Agency (ESA) Hubble Space Telescope (HST) data on the four outer moons of Pluto in order to study this strange system in greater depth. Their observations reveal that at least a duo of Pluto’s moons are not rotating on their axes in an orderly manner at all, but are instead in chaotic rotation while circling Pluto and its large companion moon, Charon–a moon-world that weighs-in at a hefty 11% of Pluto’s mass. Charon is commonly thought to have once been a part of Pluto itself, before it was blasted off in a catastrophic collision with another object billions of years ago. The new study also suggests that one of the mystery moons has a bizarre jet-black coloring of unknown origin and composition. These truly amazing results appear in the June 4, 2015 issue of the journal Nature.
Almost every moon in our Sun’s family of orbiting objects, including Earth’s own bewitching, large Moon, rotates on its axis at the same speed as it orbits its parent-planet. It is for this reason that we always observe the same side of our Moon facing us on Earth. But on Pluto, things work a bit differently. Astronomers have now discovered that there are no hidden sides to its moons!