The Search for Pluto Turns 100 in Spectacular Fashion
This story has been updated.
A NASA mission called New Horizons soared past Pluto and its largest moon, Charon, at 7:49 A.M. Eastern time. The basic facts need no embellishment:
By the early 1990's, NASA scientists saw that there was a once-in-200-years opportunity to send a spacecraft to Pluto. In 2006, New Horizons launched. In the years since, it's traveled more than 3 billion miles, flying at speeds greater than 30,000 miles per hour. It will take nearly a year and a half to send back all of the data that New Horizons has collected. The spacecraft is expected to send back an "A-Okay" message to NASA around 4: 30 P.M. Tuesday—it's too busy taking in data before then.
New Horizons offers all the whiz-bang of many NASA missions; even more given the distances involved. But it also offers something else: a century-long example of how science dreams big dreams and just as easily destroys them.
Pluto is the story of an incredibly shrinking planet.
The businessman and astronomer Percival Lowell laid out an argument for the existence of another huge planet beyond Neptune, called "Planet X," in 1915. In the same year, his team—they discovered years later—had photographed Pluto with their telescope.
Pluto was formally discovered in 1930, but it was clearly much smaller than Lowell's hypothesized Planet X. His team was looking in the right place for the wrong planet. In the mid-1970s, astronomers studying Pluto on radio telescopes concluded it may have a diameter of less than half the moon's, or 2,050 miles. Based on fresh observations from New Horizons, NASA reported Monday that its diameter is actually just 70 percent of that, just 1,473 miles.
Pluto's fortunes changed forever in 1992 when U.S. scientists reported that they'd discovered an object from the Kuiper Belt, a hypothesized ring of rocks and ices at the edge of the solar system. The sudden proliferation of astronomical objects led them to conclude that Pluto might not be anything that special at all. They demoted it in 2006 to the status of dwarf planet "134340 Pluto." Astronomers gave us the planet Pluto and then just as methodically took it away.
In the span of just a few minutes, New Horizons has transformed the dwarf planet from an object of astronomical interest to one of terrestrial interest. Already, from photos taken millions of miles away, mission scientists can make out unusual surface features, such as a dark band nicknamed "the whale," and a 1,000-mile band of complex light-dark patterning.
This century-long, 3-billion-mile march will leave researchers with Earth-satellite-like resolution photos they'll study for years.
After another billion miles New Horizons will reach the Kuiper Belt, where it may study some of the oldest and most pristine material in the solar system—and send back more data to either confirm or upend what scientists think they know about what it's made of and how planets form.
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