Ever since Pluto was downgraded to dwarf planet, the cosmic equivalent of junk bond status, the solar system’s former ninth planet has been the odd guy out.
Recent discoveries have only confirmed Pluto’s reputation as a celestial wild child. It shouldn’t surprise us, but Pluto and its five moons don’t act like any of its neighbors — not by a long shot.
Thanks to the relatively stable orbit of Charon, its largest moon, Pluto almost qualifies as a binary planet — two planets in close orbit instead of just one. It is the only such planet, dwarf or not, in the solar system that fits that description.
To add to the weirdness, Nix, Hydra, Styx and Kerberos are elongated and look more like cigars than traditional moons. These moons rotate chaotically around Pluto instead of following a synchronous rotation that is typical for planets and their moons. It is also forcing astronomers to redefine what “typical” means.
Meanwhile, so little is known about these moons that humans can only guess at their size based on years of observations from the Hubble Space Telescope.
When NASA’s New Horizons spacecraft, launched in 2006, does its historic flyby of the dwarf planet in mid-July, scientists will finally be in a position to answer many of the questions about Pluto that have vexed them for nearly a century.
Earthlings may even learn enough to question whether demoting Pluto from planetary status to dwarf was the correct call after all. The distant edge of the solar system may be on the verge of getting its ninth planet back again.
Editorial by the Pittsburgh Post-Gazette
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