May 24 – Thieves In The Temple

Today’s Factismal: Planet X was renamed “Pluto” 84 years ago; it was reclassified as a “dwarf planet” eight years ago.

Though T. S. Elliot may think that naming cats is a difficult business, he’d never tried naming a planet. When Neptune was found, it took intense international negotiations to decide upon a name. And when Pluto was found, it took a team of experts. Though most people today would agree that Pluto is an excellent name, that wasn’t always the case; many people hated the name when it was announced.

Why was Pluto so hard to name? Because Pluto was found as a result of the work of many people; in some ways, the search for Pluto was one of the first “big science” projects. In the late 1800’s, astronomers thought that Uranus and Neptune were being ever-so-slightly tugged out of place by another big planet (since then, we’ve rerun the calculations and found that there isn’t any discrepancy). For want of a better name, they called the unknown orb “Planet X”. And Percival Lowell, the man who told us about the canals on Mars (which we now know don’t exist) and founded the world’s greatest observatory (since replaced by many others), was determined to be the person who found it. For two decades, he searched. And for two decades, he failed.

The two photographic plates that discovered Pluto. (Image courtesy of Lowell Observatory Archives)

Fourteen years after his death, the observatory that he founded took on a new researcher by the name of Clyde Tombaugh. Through sheer diligence, by looking through thousands of photographs taken over the past decade, Tombaugh was able to locate “Planet X”. But what to name it? By tradition, the discoverer of a planet was allowed to name it. But Tombaugh was a mere researcher and didn’t even have a college degree. So many others tried to insert themselves into the process.

Lowell’s widow wanted to name it “Constance” (which just happened to be her name). Tombaugh, it is rumored, wanted to name it “Bob” (after his best friend). And people across the country sent in suggestions, from the zany Zymal to the staid Cronus to the odd Odin. More than 1,000 different names were suggested. In the end, the entire observatory staff voted on what to name the thing, and Pluto won. And when Pluto’s near-twin moon was discovered in 1978, a similar discussion took place before it was named Charon.

Pluto and Chron, dancing out among the stars (Image courtesy NASA)

Pluto and Charon, dancing out among the stars
(Image courtesy NASA)

But that wouldn’t be the end of Plutonic controversies. When it was found, Pluto was so far away that it was just a dim light in the telescope. As a result, everything that we thought about Pluto was based on the other planets that were out there: Jupiter, Saturn, Uranus, and Neptune. All of those planets are big and gaseous (what planetologists call “jovian planets”), so the natural assumption was that Pluto was more of the same. But as telescopes got better, Pluto got smaller. It shrank from being the size of Jupiter to being the size of the Earth to being smaller than the Moon (for what it is worth, the planet Mercury is only a little larger than the Moon).

The Eris system (Image courtesy NASA)

The Eris system
(Image courtesy NASA)

And, as if that weren’t bad enough, we started seeing other objects out near Pluto that were about the same size as the planet itself. The most famous of these new planets was Eris, aptly named for the Greek goddess of discord, which was actually larger than Pluto. The astronomers then panicked over the prospect of having more than ten planets in the Solar System and led the IAU to redefine the word so that they wouldn’t have to quit using their fingers to count. (To be fair, this wasn’t the first time that the problem had arisen; it happened with the Galilean planets and with the minor planets.) As a result, Pluto and the other planets out there became known as “dwarf planets” (an appellation that was originally intended to apply to Earth). Of course, with all of the wonderful data from NASA’s New Horizons mission, there is once more a groundswell of support to redefine planet once more.

A flyover of Pluto from New Horizon's data (Image courtesy NASA)

A flyover of Pluto using New Horizon’s data
(Image courtesy NASA)

If you’d like your chance to name a planet, then now is the time to try. All you have to do is look through the data at Planet Hunters. Once you find the planet, it is yours to name!

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