Lost Planet

In Prague, astronomers promoted Pluto to the head of a celestial class. Exactly what that class should be called, however, remains unsettled

Dear Pluto. It’s nothing personal. Honest. It’s just that you were always a bit different from the other eight planets, especially in how you failed to keep your orbit, well, clean.

You’re basically round, of course, and you orbit the sun, albeit in that elliptical way of yours. Thursday’s yanking of your official “planet’’ status by the International Astronomical Union comes down to one inconvenient truth: You weren’t big enough to sweep away or incorporate your celestial neighbors, while Neptune and the others were packing on the pounds in the early millennia of our solar system. “Dwarf planet’’ isn’t so bad, is it? Welcome to the B-list, Pluto.

Institutions like the American Museum of Natural History have dissed you for years, but astronomers meeting in Prague, Czech Republic, looked set to solidify your place in the planetary pantheon only last week by essentially defining a planet as anything round that orbits the sun.

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But then, the solar system would have at least 53 planets, taxing even the best mnemonic device. The asteroid Ceres would be one! So would your biggest moon, Charon. And Xena, too, or whatever they’ll call the recently discovered sphere 2003 UB313, which is clearly bigger than you are and arguably led to your demotion. If Pluto is a planet, astronomers maintained, so is Xena.

And now, neither of you are, after an about-face by astronomers and the new label of “dwarf planet’’ along with Ceres. Even Xena’s co-discoverer, Mike Brown at the California Institute of Technology, conceded a downgrade was in the best interests of science.

In the spirit of change, some astronomers told Brown they like the name “Xena’’ and see no reason to exclude a made-for-TV warrior princess from the mythological names normally gracing celestial bodies. “If that’s so, then the next one could be called ‘Captain Kirk’,’’ Brown said.

But back to you, Pluto.

In a decision akin to naming you “Miss Congeniality’’, the astronomers meeting in Prague promoted you to the head of your own celestial class. Exactly what that class should be called, though, is unsettled.

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“Plutonian objects’’ didn’t pass muster, and geologists pointed out that a prior suggestion, “plutons’’, was taken. In the interim, you can take pride in being the grand poohbah of “trans-Neptunian objects’’, or those wan bodies pushed out of the way long ago by Neptune.

Put another way, Pluto, you are now king of the solar system’s icy dirtballs. Not that it changes our feelings for you.

“Pluto is still a fascinating object,’’ said Charles Liu, professor of astrophysics at the College of Staten Island and an associate astrophysicist at the American Museum of Natural History. “We still have a spacecraft called New Horizons speeding toward it, and once it gets there, we’re still going to learn new and fascinating things about the solar system.’’

Richard Binzel, of the Massachusetts Institute of Technology and a member of the meeting’s planet definition committee, expressed relief that your fate has finally been decided. And at least you fared better than Charon, which has been “sent back to committee’’.

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Nevertheless, your absence will be keenly felt in the memorised mantras of students trying to keep their planets straight. Binzel proposed the slightly updated mnemonic device, “My Very Educated Mother Just Served Us Nachos.’’

Will astronomers vote on it?

“I certainly hope not,’’ he said, with an audible sigh.

Pluto, we all feel your pain.

(Bryn Nelson)