Sept.
4, 2006 issue - It's a merciful thing that Clyde Tombaugh wasn't around
to see this day. Tombaugh, the ambitious Kansas farm boy who discovered the
ninth planet, Pluto, in 1930, departed Earth in January 1997, when he died
at the age of 90. And then Tombaugh departed it again last January, when
his cremated ashes were blasted into space aboard the New Horizons space
probe. But while New Horizons was streaking through the asteroid belt last
week en route to a rendezvous with Pluto in 2015, a group of astronomers
on Earth decreed that its destination now belonged to a new category of heavenly
body, a "dwarf planet." Tombaugh knew something like that was afoot before
he died, according to his 93-year-old widow, Patricia, who added that as
a man of science, he would have understood the decision. For her part, though,
she confessed some disappointment. "I feel like I sort of got demoted from
my job being the wife of the discoverer of Pluto," she told the Arizona Daily
Star. "Now I'm the wife of the discoverer of a dwarf planet."
It's
not surprising that she should care. But what about the rest of us? Why is
the world so captivated by the fate of this remote and almost invisible world
that, if it landed on Earth, would barely stretch from Boston to Tulsa? This
knob of rock and frozen nitrogen dwells so far out in the solar system—averaging
about 3.6 billion miles, or almost 40 times the distance from Earth to the
Sun—that in the 76 years since its discovery it didn't get to complete even
a third of its orbit. And, of course, it was not really its "fate" that was
at stake, but an arbitrary designation whose impact will largely fall on
textbook publishers, planetarium gift shops and astrologers. The debate and
vote by the International Astronomical Union at its meeting in Prague was
a little reminiscent of the earnest discussions a few years back about whether
the 21st century began on Jan. 1, 2000, or 2001.
But
then why was Matthew Malkan, a UCLA astronomer, deluged with e-mails from
people he hadn't heard from in years, wanting to talk about the IAU meeting
(which he skipped, although he says now if he'd realized what a big deal
it would turn out to be he might have attended). Why did Jan Weiss, visiting
the Rose Center for Earth and Space at the American Museum of Natural History,
feel a pang of sadness at the news about Pluto? "You grow up and there are
nine planets, and now there aren't," she mused. "Imagine all those dorm rooms
where they have to scrape Pluto off the ceiling."
But
the solar system we thought we knew is changing faster than most of us can
keep up with—part of a larger process of expanding our view of the universe.
Who imagined, even a few decades ago, that we would someday see up close
giant hurricane-like storms sweep across the surface of Saturn? The revisions
began as long ago as the 1970s, when the Apollo mission brought back evidence
that the moon had been formed out of a tremendous collision between Earth
and another large object. Planets, once thought to form gradually out of
coalescing dust and gas, are now viewed as the survivors of a violent process
of collision and accretion, the winners in a Darwinian competition to build
up enough gravity to control one's own orbit. A planet the size of Pluto
has no place in the 21st-century solar system. But it still has a role to
play in science, along with the hundreds of other nearby objects discovered
in just the past decade. Understanding them offers us a window on how planets
like our own are born and give rise to life.
