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Searching the skies for a planet's subtle tug

John Couch Adams could have used a Web page. England's brilliant 19th-century mathematician solved the leading astronomical puzzle of his day - deducing the existence of an unseen outer planet from its effect on Uranus's orbit. But thanks to quirky snail mail and bumbling confidantes, the initial honors for detecting what we now call Neptune went to the equally great, publicity-minded French mathematician Urbain Jean-Joseph le Verrier.

Working independently, le Verrier matched Adams's feat. While Adams sent notes about his work to England's Astronomer Royal, who neglected them, le Verrier made sure the astronomical world knew what he was doing every step of the way. Adams persuaded Cambridge University astronomer James Challis to look for Neptune, but Challis didn't bother to analyze the mass of data he collected. Meanwhile, Berlin Observatory staffer Johann Gottfried Galle took le Verrier's prediction and promptly found the prize. Challis then discovered that he would have seen Neptune first had he bothered to analyze his data.

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Such was life in astronomy's fast lane 155 years ago. Such is life in that lane today as modern Adamses and le Verriers hunt for unseen alien worlds by analyzing how their gravity tugs on their parent stars.

Author Tom Standage notes that the modern hunt suggests "a new way to look at the past." Adams and le Verrier did more than wow contemporaries with a new planet. Hindsight shows they gave astronomy a powerful new dimension - discovery through clever use of gravitational theory.

Modern astronomers carry this to cosmic lengths. Motions of galaxies suggest the presence of invisible matter. It may account for 90 percent of our universe's total mass. Dust and stars orbiting the centers of many galaxies seem to feel the grasping "fingers" of massive black holes - a grip so powerful that everything a black hole actually swallows is gone forever. And some astronomers once again wow the public with reports of planets no telescope has yet seen.

Such developments give 21st-century relevance to Standage's interesting account of one of history's great astronomical moments. This isn't primarily a tale of individual struggle for success and recognition. While Adams, le Verrier, and their proponents had their moments, this portrayal of their personalities is two-dimensional. Standage's focus - and the hero of the story - is astronomical science itself. The struggles are those of a scientific cultural community extending its reach into a new realm of achievement.

Many early 19th-century astronomers thought it disreputable to use theory to detect a planet. They had seen too many false starts and egregious errors. Adams and le Verrier broke that mindset. Many 20th-century astronomers disrespected the hunt for alien planets for similar reasons. That mindset broke within the past five years.

In 1995, Swiss astronomers Michel Mayor and Didier Queloz showed that wobbles of a sunlike star in Pegasus reflect the pull of an orbiting giant planet. American astronomers Geoffrey Marcy and Paul Butler quickly confirmed the finding. Like Challis before them, they had been amassing data without looking at it. Hindsight showed that the long-sought planet had been lurking in those data all along. Several dozen probable alien planets now are known.

Adams and le Verrier didn't win their day immediately. Critics carped about analytical errors and misidentification of Neptune. As this review was being written, an e-mailed press release reported a critic's claim that as many as half of those several dozen alien "planets" are misidentified. Deja vu anyone?

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Robert C. Cowen writes about science for the Monitor.

(c) Copyright 2000. The Christian Science Publishing Society