Tuesday, January 03, 2006

And Then There Were Eight

Copyright © 2005 by Joel Marks
Originally published with the title “Discovery of 10th planet may mean there really are only eight” in the New Haven Register on August 3, 2005 (page A6)

At first I was excited to learn that a tenth planet has just been discovered in our solar system. But a moment's reflection made me realize that this probably means there are only eight planets.

How could that be? The status of the ninth planet, Pluto, has been in question ever since a new category of solar system object was discovered, which are now collectively known as the Kuiper Belt. Analogous to the ring of asteroids that orbit the Sun between Mars and Jupiter, these are tens of thousands of planetoids that orbit the Sun beyond the orbit of Neptune.

That is also where Pluto spends most of its time (although Pluto's eccentric orbit sometimes brings it closer to the Sun than Neptune). So there has been the surmise that Pluto may not be a planet but simply the largest member of the Kuiper Belt of planetoids. I am afraid that the discovery of a new Kuiper Belt object that is even bigger than Pluto may sound the death knell for Pluto's planetary status.

This makes me sad. To lose that planet is to lose a world – the world of ”nine planets,” which is as axiomatic as “The Earth is round” and as dear to this former little boy's heart as the sky shows at the old Hayden Planetarium in New York City. That lonely outer orb in particular has always held a special allure for the imagination.

But for me Pluto has had in addition very personal significance. First and foremost is that my twin goddaughters were born on February 18, 1970, the fortieth anniversary of Pluto’s discovery. It only added to that delightful "conjunction" to have Pluto itself turn out to be the closest there is to twins in our solar system. In 1978 James Christy discovered that "Pluto" really consists of two objects very close together, whose relative sizes make them unique. Prior to that, Earth's Moon had been thought to be the largest satellite relative to its planet, but the newly discovered Plutonian satellite, named Charon, is more than half the size of its planet.

A close second to my excitement about that cosmic coincidence was my having met the man who discovered Pluto itself, Clyde Tombaugh. When I learned that he was going to be speaking in Boston some years ago, I determined to make a pilgrimage to shake his hand. The idea of having physical contact with a human being who had been integral to the history of our solar system, and had even, as it were, "capped" that history, thrilled me no end.

I did meet and speak briefly with him. I eyed the massive hands of this former farm boy, but, when I reached out to shake one of them, alas, he refused! He said that his hand was tired from having autographed so many posters. Of course I bought one and later presented it to my goddaughters.

More recently the big news has been that planets have been discovered circling other stars. In only the last decade scores of new ones have been found! So Pluto had already been getting crowded out before this latest find in our own solar backyard.

Thus I suppose I should not have been surprised or even dismayed that the story about this latest discovery appeared only on page 2 of last Saturday’s New Haven Register. Pluto’s discovery had been front-page news. Indeed the account of Pluto’s discovery is itself a fascinating astronomical detective story and was also connected tangentially to the search for intelligent life on Mars undertaken at Percival Lowell's fabled observatory in Flagstaff, Arizona.

The Register article does have a silver lining, however, for it reports that a local person was involved in this latest planetary discovery: David L. Rabinowitz, a research physicist at Yale. You can be sure that I will look him up and hope that he does not refuse to shake my hand!

Two more essays about Pluto: A Planet by any other Name and Dueling Designations.

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