Despite ruling, Pluto still fascinates local astronomer

WILLMAR -- Pluto has been officially ousted from the planetary club, but its mystery and fascination remain alive for local astronomer William Sheehan.

WILLMAR -- Pluto has been officially ousted from the planetary club, but its mystery and fascination remain alive for local astronomer William Sheehan.

If anything, the reclassification of this icy inhabitant of the outer fringes of the solar system could help reframe how humans view the solar system and its origins, said Sheehan.

"It might help people realize the solar system is indeed more complex than we had realized," he said. "I think it will create that sense of the solar system as a very dynamic place. Ultimately it's a question that relates to our own identity."

Pluto -- discovered in 1930 and named for the Greco-Roman god of the underworld -- now belongs to a new category of heavenly bodies known as dwarf planets.

Its status was decided Thursday by the International Astronomical Union, which met in Prague to settle the definition of what is -- and isn't -- qualified to be a planet.


Under the new definition, Pluto is no longer eligible.

It's a decision that Sheehan, a psychiatrist, writer and amateur astronomer living in Willmar, agrees with.

"Science should be revised every now and then," he said. "I probably would have voted the way everyone else did."

Sheehan wrote extensively about the planets in "Worlds in the Sky," a book he published in 1992.

He's revising the chapter about Pluto and hopes the new edition will be the first publication in print that addresses Pluto's altered status.

Sheehan also has personally met Clyde Tombaugh, the astronomer who discovered Pluto and who continued searching for other planets until he died in 1996.

Pluto's reclassification as a dwarf planet is the latest in a centuries-long series of discoveries that have added, bit by bit, to humankind's knowledge of the universe.

The fascination with planets goes back to ancient times, Sheehan said. "People noticed these wandering bodies in the night sky. They worshiped them as divine beings."


Over the centuries, their understanding expanded. First Copernicus asserted that Earth revolves around the sun; then, in 1609, Galileo turned his telescope toward Jupiter and spotted a moon orbiting the giant planet.

In 1781, Uranus was discovered in the dark reaches beyond Saturn. This was followed by the discovery of Neptune in 1846, then that of Pluto almost 100 years later.

At least two generations of school children have grown up learning that little Pluto, a dark icy rock that takes 248 years to orbit the sun, represented the outermost edge of the solar system.

That changed in 1992, when the first object was found in what's known as the Kuiper Belt, a field of frozen debris in the outer solar system.

"Now there are hundreds known," Sheehan said. "The number of asteroids that have been discovered had risen astronomically, so to speak. We realized the outer solar system is much more complex... The more we learned, the more gray areas we've found."

Because Pluto is small -- it's smaller than Earth's moon -- and has an irregular orbit, many astronomers felt ill at ease including it in the planetary family, Sheehan said. Those feelings were further cemented in 2003, when an object larger than Pluto, nicknamed Xena, was discovered in the Kuiper Belt.

"This is a matter of definitions. It's not really about science," Sheehan said. "I think ultimately the new classification is going to reconcile us to the increased discrepancies. It makes sense from the standpoint of strict logic."

Sheehan, who first studied the stars through a backyard telescope at the age of 9, thinks there'll be some disappointment that Pluto is no longer considered a planet.


"I think there's a certain amount of sentiment to it," he said. "It sort of was the favorite object of the grade school folks. They were charmed by Pluto."

He hopes one of the outcomes of the debate over Pluto will be a renewed interest in the world of the solar system and beyond.

Pluto's identity "is one of the few subjects that has aroused public interest because it's something they can take a stand on. They've become engaged," Sheehan said. "All the resonance and all the romance will still be there. There's still an infinite amount to explore."

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