Pluto and Charon
Of The Planets, Asteroids and Trans-Neptunian Objects
Rights for Pluto, Xena and Sedna?
How many planets are there? Eight, nine, ten, more? Is Pluto a planet? What about the other so-called
heavenly bodies astronomers are discovering?
14-25, 2006 Pluto and some of its neighbors are getting a turn in the celestial spotlight, or finding themselves on the chopping block, depending on how you look at it. During this time the International
Astronomical Union will decide on the definition of a planet as
well as what to officially name some of the newest denizens of the solar system.
Pluto was discovered in 1930 by 24-year-old Clyde Tombaugh. Crowned the ninth planet and named for
the Roman god of the underworld, it became an international sensation and drummed up plenty of good PR for astronomy. People went so Pluto-crazy that Walt Disney even named a cartoon
character in Pluto's honor, leaving many children born in later
years assuming that the planet had been named after the dog, not
the other way around.
Pluto has since faded in importance compared to the rest of the planets. My science teacher once taught us this mnemonic device for remembering the planets: "Mercury, Venus, Earth, Mars and Jupiter form Mary Very Easily Makes Jam, then SUN, which stands for Saturn, Uranus and Neptune, and then there's Pluto, out in the doghouse."
We forget how much there is to appreciate about Pluto. According to
Dr. Alan Stern in Pluto
at 75: A Uniquely American Anniversary: "Not even Tombaugh
and his mentors could have forecast how fascinating their new planet
would turn out to be. For eventually, when the technology of astronomy
made the detailed investigations of bodies as far away and faint
as Pluto-Charon possible, this distant planet-satellite pair turned
out to be full of enticing surprises. For the ninth planet was revealed
to be the first known world with a satellite so large it could be
called a double planet, a world with complex seasons and a chaotic
orbit, and the only planet with an atmosphere that freezes out and
then is reborn every orbit. Pluto, replete with polar caps and fresh
snows of not one, but three exotic surface icesmethane, nitrogen,
and carbon monoxideis an exotic wonderland on the ragged edge
of the solar system's vast outer wilderness."
just discover Pluto, he also opened the door to the discovery of
what Stern calls the solar system's third major zone, "the
distant and icy Kuiper Belt."
So what is a planet?
If size is an indicator, Pluto doesn't have much going for it. Its
mass is only .2 percent of Earth's. It's smaller than not only all
the other eight planets but also than seven of their moons, including
our own moon. There's speculation that Pluto and its moons are simply
some of Neptune's moons knocked off course or just one of many
Kuiper Belt objects that have wandered into the Sun's gravitational
pull. In fact, the American Museum of Natural History demoted Pluto
to "Kuiper Belt object."
Pluto and the
moons: Charon, Hydra and Nix
Pluto appears to consist of rock and ice. The fact that it does
have a moon should count for something. As if realizing its status
was shaky, Pluto seemed to conveniently muster up two additional
moons (discovered in February 2006 and named Hydra and Nix) as if
to say, "Hey, guys, look! I've got three moons, not just one!
How about it?"
We know now that the solar system is a lot more crowded than was presumed in 1930. Rather than being out in the doghouse, Pluto has plenty of company in the Kuiper Belt, and the Oort cloud.
along came 2003 UB313. It's larger than Pluto. It has a moon. Some astronomers
say you don't let Pluto in the club without letting it in as well.
Brown, one of the discoverers of UB313: "There is no good
scientific way to keep Pluto a planet without doing serious disservice
to the remainder of the solar system."
The IAU currently
refers to UB313 as a Trans-Neptunian
object. At the conference, the organization will determine its status,
as well as its name. UB313 is currently code-named Xena after TV's
warrior princess character; its moon is called Gabrielle
after Xena's sidekick.
Planet Xena with
its moon, Gabrielle
Lucy Lawless as
Xena, warrior princess
Xena and Gabrielle are only code names and "There is no chance
whatsoever that these will become the permanent names of these objects!"
What could beat Xena? Not only is it the coolest name ever for a
planet, but it rather adequately describes how Xena the warrior
planet stole the thunder of Sedna (2003 VB12), discovered in 2004 and code-named
for an Inuit goddess who mostly stays under water. Sedna has gone
from being a possible tenth planet contender to merely
an asteroid (its official name is to be decided by the IAU
Committee on Small Bodies Nomenclature).
Okay, if the
name "Xena" doesn't cut it, how about "Mrs. Peel"
in honor of the character played by Diana Rigg on "The Avengers"? Or better yet, "Diana," which is, after all, also the
name of a Greco-Roman goddess and can thus keep purists happy.
Diana Rigg as Mrs.
Emma Peel in "The Avengers"
what is the answer? Do we grandfather in Pluto, giving it honorary planetary
status for its 76 years of good behavior? Do we extend our hands and welcome
everyone to the party? Or do we treat Pluto, Sedna and Xena like a bunch
of pathetic wanna-be social climbers? After all, as Christine Lavin so
eloquently put it in her song "Planet
X": "It's Pluto the planet they love, it's not Pluto the
comet, it's not Pluto the asteroid they wonder about above."
So far, it appears
that the IAU will
not demote Pluto. According to the IAU: "Recent news reports
have given much attention to what was believed to be an initiative by
the International Astronomical Union (IAU) to change the status of Pluto
as the ninth planet in the solar system. Unfortunately, some
of these reports have been based on incomplete or misleading information
regarding the subject of the discussion and the decision making procedures
of the Union. No proposal to change the status of Pluto as the ninth planet
in the solar system has been made by any Division, Commission or Working
Group of the IAU responsible for solar system science. "
But it's a rather hollow victory. While the the rest of us ignoramuses may rejoice at Pluto's reprieve, astronomers know better. In a sort of insider-ish, wink-wink, nudge-nudge fashion they are indulging in the knowledge that Pluto has simply been given cultural, historical, and sociological planetary status to please the populace, and this doesn't add up to much from a scientific standpoint.
Perhaps the solution
is for us to simply thumb our noses at the whole planetary status thing.
Who wants to be a planet anyway, when it's way cooler (literally and figuratively)
to be a Kuiper Belt or Oort Cloud object? Who needs those insular planets who can't
see past their own sun when you can have one eye on the solar system
and the other looking far out over the rest of the galaxy? Being a KBO or OCO could
be the ultimate in outsider chic!
Fans of Pluto, Xena,
Sedna et al await the IAU's decision and look forward to what the future
Horizons, carrying a canister with Tombaugh's ashes, is set to encounter
Pluto in 2015 and head into the Kuiper Belt in 2016.
Update: Pluto was
in fact demoted, saddled with the designation of "dwarf planet."
Fellow dwarf planet and moon Xena and Gabrielle were named Eris and Dysnomia,
respectively. Eris is the Greek goddess of discord and strife; Dysnomia
is her daughter, the spirit of lawlessness. According to the IAU Eris's
claim to fame is that after being left off the guest list to an exclusive
wedding, she retaliated by causing a quarrel that led to the Trojan War.
fans are rallying to the cause. You can read up on their doings at the
for the Preservation of Pluto as a Planet (and make a donation to
the cause?) or buy a "Honk if Pluto is still a planet" bumper
sticker or a "Save Pluto" T-shirt . Yes, there's money to be
made from Pluto's plight.
Box 580, New York, NY 10113 ©2006