Where the Wild Things Are
We’re about to get a peek at the solar system’s final frontier.
- By Guy Gugliotta
- Photographs by Illustrations by Ron Miller
- Air & Space magazine, July 2009
Illustration by Ron Miller
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But scientists were slowly advancing their understanding of the outer solar system. In 1950, Dutch astronomer Jan Hendrik Oort theorized that there was a huge spherical cocoon of icy debris surrounding the solar system beyond Pluto and extending as far as a light-year away. These pieces, flung out by the giant planets, were the source of “long-period” comets, which enter the solar system from all angles and have orbits of thousands of years. During the 1980s, astronomers learned a lot more about Pluto, especially during a series of mutual eclipses between Pluto and Charon that lasted five years. The study was made possible because the Pluto-Charon orbital plane could be seen edge-on from Earth, a phenomenon that happens only twice during Pluto’s 248-year orbit of the sun. Pluto’s color, astronomers found, was yellowish pink, tending toward scarlet. The surface had methane ice, contrasting areas of dark and light, and one or maybe two polar caps. At this point Pluto began to acquire a new identity: a tiny, intriguing outlier. “We began to ask why we should believe that everything stopped at Neptune,” says Jewitt. “If there was Pluto, why not something else?”
In 1985, Jewitt and Luu started hunting. They began as Tombaugh had—comparing photographic plates by eye—then switched to charge-coupled devices and digital imaging. “Our first few searches produced nothing, but we kept on looking because the technology kept evolving,” Jewitt recalls. “We’d get burned out, but then we’d get a new CCD and get all charged up again.”
Meanwhile, in 1989, Stern, a doctoral candidate and Pluto buff, joined several colleagues in what they called a “Pluto underground” to urge NASA to explore the only planet in the solar system that a spacecraft had not visited. Stern says he was convinced that scientists had “pretty much used up our [astronomical] bag of tricks,” and were reaching the limit on what they could determine from telescopes. “There was only one way to learn more about Pluto,” he says. “We had to go there.” Stern pushed hard through the 1990s, as NASA planned and scuttled four separate Pluto projects before finally awarding the mission to New Horizons in 2001. For $700 million, the project would use what Weaver calls the “elephant gun” approach: Take the biggest rocket available, make the payload as small as possible, point the gun at Pluto, and pull the trigger.
In 2006, with New Horizons en route, the International Astronomical Union stripped Pluto of its “planet” status, created a new class of celestial body called “dwarf planet,” and made Pluto and the newly discovered Eris the first two members. A dwarf planet had enough gravity to be round, the Union said, but was not massive enough to suck up the material in the area around its orbit. Cal Tech’s Brown, who had hopes of joining Tombaugh as the only Americans to discover a planet, instead became the second person to discover a dwarf planet. “We’re cleaning up a scientific mistake,” Brown says. “It’s hard to look at the solar system and not quickly come to the conclusion that there are eight large objects, and Pluto is not one of them.” Pluto, it turns out, was something altogether different: the gateway to the Kuiper Belt.
Guy Gugliotta is a former space reporter for the Washington Post.