Jimmy Westlake: Planet potpourri


Jimmy Westlake

Jimmy Westlake's Celestial News column appears monthly in the Steamboat Today.

Find more columns by Westlake here.

— Quietly and without much fanfare, our solar system recently gained two more named dwarf planets. They were discovered a few years ago, but it takes awhile for the official naming process to run its course.

You might recall that, in 2006, a long-standing member of the exclusive "planet club," Pluto, lost its membership when the International Astronomical Union redefined the term "planet," and Pluto got the ax. As a consolation prize, Pluto was given the official designation of "dwarf planet" (which still sounds like a kind of planet to me!). At the same time, Ceres, the largest asteroid in the asteroid belt between Mars and Jupiter, received an upward promotion to "dwarf planet" status, and the largest object discovered beyond Pluto, Eris, became the third dwarf planet.

Now come two more outer solar system objects to the ranks of dwarf planetdom. Please welcome Makemake (pronounced mah-kay-mah-kay) and Haumea (pronounced hah-oo-may-ah) to the family. Like Pluto and Eris, Makemake and Haumea are cold, icy bodies out beyond Neptune that are large enough to pull themselves into a spherical shape but are guilty of not having cleared their orbits of debris and, therefore, forfeit their memberships into the planet club. The IAU in June, though, created a new club for the icy dwarf planets beyond Neptune. Pluto, Eris, Makemake and Haumea are charter members of the Plutoid club. There are about 70 more applications to the Plutoid club that are awaiting certification.

By the way, if you are wondering about the unusual new names, Makemake's code name, given by its co-discoverer Michael Brown, was "Easter bunny." He chose the official designation Makemake because this was the chief god from the mythology of the native inhabitants of Easter Island. Haumea is the Hawaiian goddess of fertility and childbirth. It appears that this object, in fact, gave birth to a whole string of icy bodies in the outer solar system as the result of a cataclysmic impact long ago. Haumea's two known moons are now named for two of her many children, Hi'iaka and Namaka. Who says astronomers don't have a sense of humor?

Meanwhile, in another solar system far, far away, the faint glimmer of an extra-solar planet has been photographed successfully for the very first time. This planet, unimaginatively named Fomalhaut b, orbits the familiar bright star Fomalhaut that graces our autumn skies. As of Friday, 326 extrasolar planets have been confirmed by indirect measurements. Fomalhaut b is the first such planet to be photographed visually by the venerable Hubble Space Telescope.

I propose that we name this newly discovered planet "Elvis." All in favor say "aye!"


Laurel Kornfeld 8 years, 5 months ago

Pluto IS a planet because unlike most objects in the Kuiper Belt, it has attained hydrostatic equilibrium, meaning it has enough self-gravity to have pulled itself into a round shape. When an object is large enough for this to happen, it becomes differentiated with core, mantle, and crust, just like Earth and the larger planets, and develops the same geological processes as the larger planets, processes that inert asteroids and most KBOs do not have. Not distinguishing between shapeless asteroids and objects whose composition clearly makes them planets is a disservice and is sloppy science. As of now, there are three other KBOs that meet this criterion and therefore should be classified as planets--Haumea, Makemake, and Eris. Only one KBO has been found to be larger than Pluto, and that is Eris. The IAU definition makes no linguistic sense, as it states that dwarf planets are not planets at all. That's like saying a grizzly bear is not a bear. Second, it defines objects solely by where they are while ignoring what they are. If Earth were placed in Pluto's orbit, by the IAU definition, it would not be a planet. That is because the further away an object is from its parent star, the more difficulty it will have in clearing its orbit. Significantly, this definition was adopted by only four percent of the IAU, most of whom are not planetary scientists. No absentee voting was allowed. It was done so in a highly controversial process that violated the IAU's own bylaws, and it was immediately opposed by a petition of 300 professional astronomers saying they will not use the new definition, which they described accurately as "sloppy." Also significant is the fact that many planetary scientists are not IAU members and therefore had no say in this matter at all. Many believe we should keep the term planet broad to encompass any non-self-luminous spheroidal object orbiting a star. We can distinguish different types of planets with subcategories such as terrestrial planets, gas giants, ice giants, dwarf planets, super Earths, hot Jupiters, etc. We should be broadening, not narrowing our concept of planet as more objects are being discovered in this and other solar systems. In a 2000 paper, Dr. Alan Stern and Dr. Hal Levison distinguish two types of planets--the gravitationally dominant ones and the smaller ones that are not gravitationally dominant. However, they never say that objects in the latter category are not planets. I attended the Great Planet Debate, which actually took place in August 2008, and there was a strong consensus there that a broader, more encompassing planet definition is needed. I encourage anyone interested to listen to and view the conference proceedings at http://gpd.jhuapl.edu/ You can also read more about this issue on my blog at http://laurele.livejournal.com


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