Pluto and Eris: planets that didn’t make it.

With the news today that Pluto is finally going to be photographed, the outer rim of the solar system is receiving a lot more attention than it normally does. Not since Pluto was dropped from the list of planets has it received so much coverage. As part of the segue to the weather report on CBC Newsworld this morning they even gave out the temperature on Pluto (v. cold).

"Pluto animiert 200px" by Aineias, NASA, ESA, and M. Buie (Southwest Research Institute)derivative work: Aineias, Ilmari Karonen - Pluto_hubble_photomap.jpg via Pluto_animiert.gif. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Pluto_animiert_200px.gif#mediaviewer/File:Pluto_animiert_200px.gif

Animated map of Pluto

Pluto is the perfect example of how things can change. Back in the nineties I wrote a book called Sun, Moon and Stars, in which I stated that Pluto was a planet, and had one moon. Now, Pluto has been demoted, and has five moons. (Having said that, there were rumblings about the ninth planet’s status even then.)

I can’t help but think that Pluto/Hades, the god the then-planet was named for, had a cap of invisibility that let him fly under the radar, and a score of assistants to help him deal with the souls of the dead.

God of the Underworld, and Kerebos.

God of the Underworld, and Kerebos.

Pluto’s moons include:

  • Charon: ferryman of dead souls across the river Styx
  • Nix: goddess of night, mother of Charon
  • Hydra: nine-headed serpent, defeated by Hercules
  • Kerebos: the dog that guarded the entry to the underworld
  • Styx: river that separated Hades from the land of the living

I still cherished the illusion that Pluto was somehow unique, even when they seem to be discovering planets everywhere. Unfortunately, the aptly-named Eris came along to upset the apple cart.

Eris would have been the 10th planet if certain people weren’t so picky about things like size, since it’s about as big as Pluto. Apparently the discovery of Eris, far from making a nice round number of planets, precipitated Pluto’s fall into dwarf status.

Eris is named for the goddess of Discord, who broke up the wedding of Cadmus and Harmony by throwing an apple inscribed “to the fairest” into the banquet hall. Hera, Athena and Aphrodite all assumed it was meant for them, a young man named Paris was asked to choose, and, when Aphrodite gave him the most beautiful woman in the world as his bribe, the stage was set for the Trojan War.

Winged Eris

Winged Eris

Luckily, this disharmonious planet is extremely far away, taking 561 years to circle the Earth. It rotates on its axis in 25 hours, so its day is about as long as ours. One nice touch is that its moon is named Dysnomia, after Eris’ daughter. Eris is thought to be rock, with a thin layer of ice over the top. According to the NASA page on Eris, it thaws as it approaches the Earth and then freezes again, since like Pluto it has an elliptical orbit. (Oval rather than round.)

Still, the god of the dead must be glad of the company. It’s lonely out there in the Kuiper Belt.

(The bullied Pluto image comes from Let’s Learn About Space, on Tumblr.)

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3 thoughts on “Pluto and Eris: planets that didn’t make it.

  1. Pingback: Happy Birthday, Clyde Tombaugh! – We Are Star Stuff

  2. Pingback: Ceres: asteroid to dwarf planet – We Are Star Stuff

  3. Pingback: Vulcan: the planet that never was – WE ARE STAR STUFF

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