BOB NANDELL/The Register

Steve Kawaler, an Iowa State University physicist, shows a map of the globe with flags marking the astronomy observatories that will be linked together by computer to study a white dwarf star 11 light years from Earth.

Ames, Ia. - The childhood rhyme "Twinkle, twinkle little star" has a different meaning for Steve Kawaler than for most adults - particularly the line, "like a diamond in the sky."

That may he exactly what some stars are, said Kawaler, a professor of physics and astronomy at Iowa State University. To find out, the global alliance of scientists he heads will soon be turning telescopes skyward to focus on an unusual white dwarf star.

"It's a pretty wild theory," Kawaler said. The round-the-clock observations could represent "the very first opportunity we have ... to directly say that a star's interior is crystalline."

If the theory is correct, Kawaler said the core of the star, BPM 37093, is composed of crystalline carbon - diamond, in other words. It could be as large as 5 times 10 to the power of 33 carats - that's a 5 with 33 zeroes after it, Kawaler said. The largest diamond ever mined, by comparison, is a puny 3,106 carats.

It probably isn't the kind of diamond someone would want on their wedding ring, however. If one theory holds true, "It's impure diamond, because there's oxygen and a few other heavier elements in it," Kawaler said. "It may be it's more industrial quality than gem quality."

Another theory, however, says the oxygen could have precipitated out of the mixture, creating instead a diamond shell holding "snowflakes" of oxygen, Kawaler said.

That's what makes the star more than just 3~ novelty. Its structure could provide clues to the age of our galaxy. Researchers believe it also could tell us things about our own sun's aging process.

BPM 37093 is located in the constellation Centaurus, visible only from the southernmost parts of the United States or in the Southern Hemisphere. It's about the size of our Earth, but is composed of extremely dense matter. "One teaspoon weighs as much as all the New York Yankee infielders," he said.

Unlike most white dwarf stars, scientists believe BPM 37093 is so massive it has crystallized while it is still pulsating - emitting varying degrees of light on a regular cycle. That's what Kawaler believes will help astronomers learn more about what makes up the star.

From April 16 to May 4, the Whole Earth Telescope, a team of astronomers Kawaler directs, will measure and record the pulsations.

But watching a star from one lccation, just when it's out at night, isn't good enough. Pusations can occur on a time scale of one day or longer. Watching a star just at night would miss those patterns, he said.

To overcome that handicap, the Whole Earth Telescope was devised in 1986. The project, now based at ISU and headed by Kawaler since 1997, joins 20 institutions in countries such as Uzbekistan, South Africa and France. The project is under the auspices of ISU's International Institute for Theoretical and Applied Physics with support from the National Science Foundation.

Once or twice a year, scientists at telescopes around the globe focus on a single object in the sky, allowing around-the-clock observations.