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The Perils of Killing a Planet

A young astronomer riffs on the thrills and chills of pursuing planetary science in the Internet age

In How I Killed Pluto (subtitled “and Why It Had It Coming”), California Institute of Technology astronomer Mike Brown spins a witty tale of his search for a tenth planet, his discovery of Eris (a body larger than Pluto and orbiting the sun four times farther out), and the ensuing controversial demotion of Pluto as a planet. This book is his genial way of explaining why that act of Plutocide was a beneficent move.

The seeds of Brown’s revolt against Pluto as a planet were sown early in his life. Perhaps you recall some variant of this school-days mnemonic for the names of the planets and their order from the Sun: “My Very Excellent Mother Just Served Us Nine Pizzas” (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto). The version Brown learned as a third-grader in his hometown of Huntsville, Alabama (where his father and “the father of everyone I knew” were engineers working on NASA moon rockets), went like this: “Martha Visits Every Monday and Just Stays Until Noon. Period.”

Brown always suspected it was “dumb luck” that the “and” falls between Mars and Jupiter, where the asteroid belt lies. But the “Period” for Pluto at the end “seemed fishy even in third grade.” To Brown’s mind, that full stop relegated Pluto to the status of “an afterthought or a late addition or just perhaps an undesirable misfit.” The poster on the wall of young Mike’s bedroom only emphasized Pluto’s oddness—its orbit was tilted 20 degrees away from the flat disk where the other planets traveled and was so elongated that Pluto would have to head clear off the poster and halfway across the front yard before turning back in toward the sun.

Fast-forward to the late 1990s and early 2000s. Brown is now a professor of astronomy and an obsessed planet hunter at Caltech, systematically searching the skies for a tenth planet. When he is not spending long nights at the telescope and even longer hours at his computer — writing software to speed his search, or staring at starfield photos to ferret out a dot that moves — Brown is busy meeting, courting, and marrying his wife, Diane.

Then along comes a daughter, Lilah. Her arrival in the world on July 7, 2005 — somewhat earlier than Brown had calculated — delayed his completion of a critical scientific paper that was to announce the discovery of a Sun-orbiting object that his team had found just after Christmas 2004 (and therefore nicknamed Santa). Instead of finishing the paper, the sleep-deprived but ever-scientific new father plotted graphs of how long Lilah could go between feedings and posted them on her own website. Then, three weeks after Lilah’s birth, Brown got a shock when a team of Spanish astronomers suddenly announced they had discovered Santa on their own.

Well, almost on their own. In Brown’s reconstruction of events, the rival astronomers had come across abstracts of the Brown team’s papers, which identified Santa only by an alphanumeric code name. The Spanish scientists then searched the Internet for mentions of that code name, which led them to the Brown team’s telescopic observing data (a glitch — the data was supposed to be kept hidden from the public eye). With the observing data in hand, the Spaniards succeeded in plotting Santa’s orbit back in time; this in turn enabled them to look for it — and “discover” it — in old photos of the relevant section of sky.

Brown’s team, which had delayed announcing Santa’s existence as they scrambled to verify their findings, had determined that it was about one-third the size of Pluto and was orbited by two tiny moons (nicknamed, of course, Rudolph and Blitzen). The Spanish team scooped them with a bare-bones announcement of an object they claimed was bigger than Pluto — and which they were calling “the tenth planet.”

According to International Astronomical Union (IAU) protocol, whoever announces first gets to claim the discovery. Galling as it was, Brown renounced his claim to Santa in order to deflect attention from another, even more significant discovery he was about to unveil: Xena! Yes, after television’s Warrior Princess. This was the nickname Brown gave the body now known as Eris (after the ancient Greek goddess of discord), which he had first spotted in January 2005 — and which his team believed really was slightly larger than Pluto. Still reeling from the shock of losing Santa, Brown reluctantly allowed a Caltech press release to herald Xena as the tenth planet.

Ironically, this unveiling of Pluto’s near-twin — coming atop discoveries in the previous decade of several hundred smaller objects, many of them first observed by Brown himself — prompted astronomers to rethink the very definition of a planet.

At an unusually contentious conference in 2006, the IAU created the new category of “dwarf planet” to characterize Pluto, Eris, and many other similar bodies. Brown wasn’t sold on the term, but he was the first to champion the argument that neither Pluto nor Eris belonged in the same league as the big eight.

The battle is still being waged on the Internet today, with diehard Pluto-crats ranting against Mike Brown and urging the restitution of Plutonian planethood. Perhaps one of them is behind the new solar-system mnemonic that an anonymous correspondent sent to Brown: “Mean Very Evil Men Just Shortened Up Nature.”

Roberta Conlan, an editor and writer who founded the book packager EdiGraphics, divides her time between Virginia and Hawai‘i.