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.