Dance Of The Distant Moons
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 The Great Planet Official Store 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!
In this fascinating new research, the astronomers announced that they have discovered that a duo of Pluto’s moons, dubbed Nix and Hydra, are actually in a chaotic rotation. This basically means that an observer standing on the alien surface of icy, strange Pluto, would not observe the same face of its moons from one night to the next. For those observers visiting the two bizarre moons themselves, things would be even weirder because every day would be a different length from the one that came before it.
The other duo of Pluto’s five known moons being studied, Kerberos and Styx, are also currently thought to be in chaotic rotation as well! However, Pluto well may have a few more small moons that have not as yet been spotted–at least, as of this writing.
“Prior to the Hubble observations, nobody appreciated the intricate dynamics of the Pluto system,” Dr. Mark Showalter explained in a June 3, 2015 HST Press Release. Dr. Showalter is of the Search for Extraterrestrial Intelligence (SETI) Institute in Mountain View, California. He is lead author of the Nature paper.
The truth is that Pluto’s large moon Charon is a freak. Pluto and Charon do not behave like a “normal” planet-and-moon duo. In fact, the system is unique in our Solar System because the two small, icy worlds face each other and spin together around a fixed point. For this reason, many planetary scientists have suggested that Pluto and Charon actually form a binary system–rather than that of a moon and planet pair. The new research shows that the chaotic movements of Pluto’s smaller moons are caused by this weird Pluto-Charon relationship.