Pluto: The Once and Future Planet?
Clearly some kind of consensus had to be arrived at to determine what is and what is not a planet. In mid August, 2006, a panel of influential astronomers, writers, and historians established by the International Astronomical Union made some recommendations that would have changed the face of our Solar System. Not only would Pluto be confirmed as being a planet, something that was in some doubt recently, but three more planets would be added to the Solar System. These new planets would have been Ceres, hitherto considered the largest asteroid, Charon, hitherto a moon of Pluto, and a body recently discovered that has been designated 2003 UB313, but has was nicknamed “Xena” after the character in the fantasy TV series from the 1990s. The object was recently given a formal; name, Eris, after the Greek godess of chaos.
According to the panel, in order to be considered a planet, a celestial body would have to follow certain definitions. The object must orbit a star but not be a star itself. The object must be large enough that its own gravity pulls it into a nearly spherical shape. This means a planet must weigh at least one-thousandth as much as Earth and have a diameter greater than 500 miles.
The new list of planets would have been divided up into a couple of categories. Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune would have been designated “classical planets.” Ceres would have been designated a “dwarf planet.” Pluto, Charon, and “Xena” would have been designated “Pluton planets” and perhaps also “dwarf planets.”
Ceres was discovered in 1801 by Giuseppe Piazzi. It has a diameter of about 930 kilometers. It has a mass of 950,000,000,000,000,000,000 kilograms. It has a rotational period of about a third of an Earth day. It takes four and a half years to orbit the sun. It is 2.676 astronautical units (1 AU = the distance of the Earth from the Sun) from the Sun. Recent observations by the Hubble Space Telescope suggest that Ceres is covered with frost, consisting of frozen ammonia and water. It may even have a rudimentary atmosphere. The space probe Dawn is scheduled to visit Ceres in the year 2014.
Charon was discovered by James Christy in 1978. It has a diameter of about 1207 kilometers. It has a mass of 1,520,000,000,000,000,000,000 kilograms. Along with Pluto, Charon is about 39.5 AU from the Sun. It orbits a common point with Pluto every six and a third days. Even though it had been previously been considered a Moon of Pluto, for the purposes of Charon being designated a planet Charon and Pluto will be designated a “double planet.” Pluto and Charon will be visited by the New Horizons space probe in the year 2015.
Object 2003 UB313 or “Xena” as it has been nicknamed before it was formally named Eris was discovered by M. E. Brown, C. A. Trujillo, and D. L. Rabinowitz in 2003. It has a diameter of 2400 kilometers. It’s mass and rotational period are so far unknown. It orbits the sun every 557 years. It is 97 AU from the sun and therefore the farthest known object in the Solar System. However, its orbit is highly eccentric and it will be as close as 37.8 AU from the sun.
Under the new definition, many other celestial bodies might have been considered planets. For instance, if the asteroids Pallas, Vesta, and Hygeia were found to be round, they would have become planets. Other objects in the Kuiper Belt might also be considered “candidate planets.”
Thus things stood when the International Astronomical Union met in Prague in late August. The panel’s proposal, which might have expanded the Solar System to dozens of planets, proved to be too much. After some wrangling and back room dealing, the IAU decided that a planet had to be the largest object in its population of celestial bodies. That meant that Pluto and Charon, being no larger than many other objects in the Kuiper Belt, would not be planets at all. So the IAU voted to make Pluto a “dwarf planet”, which is to say not really a planet at all. That meant that instead of expanding to twelve planets, the Solar System suddenly shrunk to eight.
The end of the argument? Certainly not.
The vote to demote Pluto had involved roughly 424 astronomers who happened to attend the meeting in Prague, roughly five percent of the world’s total. The first to express outrage was Alan Stern, the leader of NASA’s New Horizon mission to Pluto, which is no longer a planet. Stern and other scientists suggest that the criteria for a celestial object being a planet was ambiguous and that under the IAU definition, planets such as Earth and Jupiter might not be planets as they share orbits with asteroids. Stern is circulating a petition to overturn the IAU decision.
Inevitably, politicians have gotten into the act. A resolution has been proposed in the California Assembly condemning the proposal. It reads as follows:
WHEREAS, Recent astronomical discoveries, including Pluto’s oblong orbit and the sighting of a slightly larger Kuiper Belt object, have led astronomers to question the planetary status of Pluto; and
WHEREAS, The mean-spirited International Astronomical Union decided on August 24, 2006, to disrespect Pluto by stripping Pluto of its planetary status and reclassifying it as a lowly dwarf planet; and
WHEREAS, Pluto was discovered in 1930 by an American, Clyde Tombaugh, at the Lowell Observatory in Arizona, and this discovery resulted in millions of Californians being taught that Pluto was the ninth planet in the solar system; and
WHEREAS, Pluto, named after the Roman God of the underworld and affectionately sharing the name of California’s most famous animated dog, has a special connection to California history and culture; and
WHEREAS, Downgrading Pluto’s status will cause psychological harm to some Californians who question their place in the universe and worry about the instability of universal constants; and
WHEREAS, The deletion of Pluto as a planet renders millions of text books, museum displays, and children’s refrigerator art projects obsolete, and represents a substantial unfunded mandate that must be paid by dwindling Proposition 98 education funds, thereby harming California’s children and widening its budget deficits; and
WHEREAS, The deletion of Pluto as a planet is a hasty, ill-considered scientific heresy similar to questioning the Copernican theory, drawing maps of a round world, and proving the existence of the time and space continuum; and
WHEREAS, The downgrading of Pluto reduces the number of planets available for legislative leaders to hide redistricting legislation and other inconvenient political reform measures; and
WHEREAS, The California Legislature, in the closing days of the 2005-06 session, has been considering few matters important to the future of California, and the status of Pluto takes precedence and is worthy of this body’s immediate attention; now, therefore, be it
Resolved by the Assembly of the State of California, That the Assembly hereby condemns the International Astronomical Union’s decision to strip Pluto of its planetary status for its tremendous impact on the people of California and the state’s long term fiscal health; and be it further
Resolved, That the Assembly Clerk shall send a copy of the resolution to the International Astronomical Union and to any Californian who, believing that his or her legislator is addressing the problems that threaten the future of the Golden State, requests a copy of the resolution.
Of course, the once and possibly future planet Pluto has nothing to do with the Disney character. It was named after the Roman god of the underworld. As for the decision causing psychological harm to the good people of California, one should just pass over that “WHERAS” without comment.
While one would expect this sort of thing from California, the city fathers of Madison, Wisconson have gotten into the act with the following resolution:
WHEREAS, the International Astronomical Union (IAU) has recently declared that Pluto is no longer a planet of our solar system and is instead part of a new category of planets that they intend to name “dwarf” planets; and
WHEREAS, one of the reasons for this demotion is that Pluto is small, which they call being a “dwarf,” suggesting the IAU does not tolerate diversity; and
WHEREAS, Pluto’s orbit intersects the orbit of Neptune and is somewhat elliptical, which also is being used as a reason for disqualifying it as a planet, suggesting that the IAU really does not tolerate planets pursuing different lifestyles; and
WHEREAS, there are two other astronomical bodies – UB313 and Ceres – that could also qualify for planetary status were we to be consistent with declaring Pluto a planet; and
WHEREAS, while UB313 has been nicknamed Xena after a noted television character very popular with the lesbian and gay community, the IAU has resisted making this name official, again suggesting a level of intolerance; and
WHEREAS, “plutocracy” means the reign of wealth or the wealthy; and
WHEREAS, the Mayor has expressed concerns that, should this resolution pass, Madison might be perceived as a plutocracy;
NOW, THEREFORE, BE IT RESOLVED that the City of Madison declares that Pluto is its ninth planet.
BE IT FURTHER RESOLVED that the City supports Pluto and values its dwarf status.
BE IT FURTHER RESOLVED that the City supports planets that take a different path, such as Ceres and Xena.
BE IT FURTHER RESOLVED that the City requests Neptune modify its orbit to assist Pluto in qualifying for planetary status and that Neptune declare this to be a reasonable astronomical accommodation.
BE IT FURTHER RESOLVED that the city urges the IAU to adopt an Inclusionary Astronomy rule giving planets that might be small, have elliptical orbits and exist with differences equal status to the other planets.
BE IT FURTHER RESOLVED that the City declares it is not in any way favoring a plutocracy.
BE IT FURTHER RESOLVED that the City believes that Inclusionary Astronomy is also a way to counter any suggestion that this resolution endorses plutocracy.
BE IT FURTHER RESOLVED that the City requests the International Astronomical Union to reconsider its decision, to grant Ceres and UB313 planetary status, and to give UB313 the name Xena as a gesture of inclusiveness.
BE IT FINALLY RESOLVED that the City invites any representatives of Pluto (should any exist) to an upcoming Common Council meeting where they will receive the keys to the city, passes to the Goodman Pool, an honorary membership in the Chamber of Commerce (to ensure that the folks on Pluto realize how business-friendly Madison really, REALLY is) and, finally, an autographed CD from the Dixie Chicks.
Of course, one supposes that renaming “Xena” to “Eris” is a slam against the gay and lesbian community as well.
Of course, no cause can be complete without one protest song. Subplot A, an indie group from Canada, has released a song protesting the demotion of Pluto called “Pluto Rocks.” The lyrics go like this:
So smart and so smug, so proudly pedantic
Can’t you be a scientist and still a romantic
Don’t you still love him, don’t you still need him
Don’t you want your great great grandkids to meet him
I don’t care what people say, you’ll always be mine
I don’t care what the experts say, you’ll always be my number nine
Pluto rocks, in a vacuous void
Grandfather Pluto, he’s no asteroid
Pluto rocks, stop the attack
Grandfather Pluto, you gotta bring him back
The controversy is bound to continue. This writer predicts that, one way or another, Pluto is going to be restored to its position as a planet. Over three quarters of a century of tradition will trump ambiguous criteria developed by small groups of scientists every time.
