Nobody Killed Pluto

a book review by Karen A. Bellenir

Just for the record: Nobody killed Pluto. It's still out there, participating in a grand celestial dance that involves a host of other objects orbiting our sun.

But Mike Brown, the self-identified killer of Pluto, did play a role in the events that led to its reclassification as a dwarf planet. In his delightful memoir, How I Killed Pluto and Why It Had It Coming, Brown recounts his own relationship with the planets and his dream to locate a tenth. Instead, his quest culminated in a reordering of the way we conceptualize our solar system.

As Brown explains, new scientific discoveries can have a way of wreaking havoc with established classification systems. He recounts the history of the word planet, which originally meant "wanderer." It was used to describe lights in the sky that moved differently from the stars. In antiquity, the roster of planets comprised these seven: The Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn. When it became clear that the Sun rather than Earth stood in the center of the solar system and that the Moon orbited Earth rather than the Sun, the planetary list changed: Mercury, Venus, Earth, Mars, Jupiter, and Saturn. Six planets.

The situation didn't remain static for long. A new-fangled technology, the telescope, enabled William Herschel to discover Uranus in 1781. Seven planets. Then Giuseppe Piazzi discovered Ceres in 1801. Eight planets. And Heinrich Olbers discovered Pallas 1802. Nine planets. Other astronomers found Juno in 1804 (ten planets) and Vesta in 1807 (eleven planets). Later, in the middle of the nineteenth century, Neptune made it an even dozen.

If you don't recognize Ceres, Pallas, Juno, and Vesta as planets, it isn't because you slept through an astronomy lesson. They were discovered orbiting the Sun in the region between Mars and Jupiter. And, astronomers kept finding other objects in that area of space.  The objects weren't quite like the other planets, however. When viewed through the best telescopes of the day, the other planets could be seen as round disks. These newly located objects were merely points of light, more similar in appearance to the distant stars. Eventually, they were classified with a new identifying label: Brown explains that term's origins: "Aster is Greek for 'star,' as in astronomy, while oid means 'like'." Ceres, Pallas, Juno, and Vesta were thus demoted to the rank of asteroid, and the solar system went forth with just eight planets.

Then in 1930, Clyde Tombaugh discovered Pluto. Unlike the asteroids, which were nearby in comparison, Pluto was farther away than Neptune. Admittedly, it was a bit odd. Pluto's orbit was tilted about 20 degrees from the plane of the other planets, and its orbital path was so elliptical it sometimes traveled closer to the sun than Neptune. Nevertheless, with no other labels to better suit it, Pluto was designated the ninth planet. Throughout the rest of the twentieth century, school children learned the order of the nine planets with this mnemonic: My Very Energetic Mother Just Served Us Nine Pizzas.

That is, until Mike Brown started to shake things up. In the distant reaches of the solar system, he found several other objects past Neptune. His book recounts the twists and turns involved in seeking illusive hints of these distant wanderers. He tells of writing specialized computer code to analyze images and the challenges of waiting to schedule observing time on the world's most advanced telescopes, including the Hubble Space Telescope. The tale includes elements from stories of espionage, including code names for astronomical targets, being the victim of computer hacking, and anxious days of waiting while balancing the need to confirm facts with the urgency of making announcements before being "scooped." Brown's personable account even includes some romance and warm family moments.

Ultimately, Brown's story moves toward the discovery of Eris and its moon Dysnomia. Eris, estimated to be slightly larger than Pluto, could have been called the tenth planet. Instead, it created a controversy that culminated in the coining of another new term for describing some of the solar system's components. In August of 2006, the International Astronomical Union passed a resolution that defined the word planet in a way that left the solar system with only eight. Pluto, Ceres, and Eris were named among a distinct class of solar system objects called dwarf planets. And Brown says "Just as Matchbook cars are not cars, stuffed animals are not animals, and chocolate bunnies are not bunnies" a dwarf planet is decidedly not a planet.

But the controversy refused to end, and recalculations of Pluto's size led some to speculate that the former planet might have a diameter of up to twenty-five miles larger than Eris. Brown concluded, "It is likely that we won't know the real size of Pluto until the New Horizons spacecraft flies by in 2015 and gets a much closer look."

That time is fast approaching. NASA launched its New Horizons mission on January 19, 2006, in an era when Pluto was still classified as a planet. It is scheduled to rendezvous with the dwarf planet this summer. Its closest approach will occur on July 14, 2015. NASA claims, "New Horizons seeks to understand where Pluto and its moons 'fit in' with the other objects in the solar system, such as the inner rocky planets (Earth, Mars, Venus and Mercury) and the outer gas giants (Jupiter, Saturn, Uranus and Neptune)." For more information, visit NASA's New Horizon's webpage.

To help people become better informed about Pluto and to understand the findings of the New Horizons mission in context, Pier Press has added How I Killed Pluto and Why It Had It Coming, by Mike Brown, to our bookstore. And, in honor of NASA's mission to explore this distant, icy world, we're putting the book on sale at 20% off through the end of July 2015.