A student of the universe at work Astronomer: A 33-year-old UCLA professor has changed the way scientists think about the birth of stars.

Sun Journal

November 30, 1998|By K. C. Cole | K. C. Cole,LOS ANGELES TIMES

MAUNA KEA, Hawaii -- In the thin air of Mauna Kea's summit, 300 tons of glass and steel pirouette as silently as a ballerina. A mile below, marshmallow clouds turn sunset pink. The red glow of still-active volcanoes on the far side of Hawaii's Big Island gleams through the overcast.

With a horrible crunch, the world's largest optical telescope drops its two jaw-like hatches one at a time, opening its twin throats to drink in starlight.

The Keck telescope is ready to receive the universe.

Waiting in the control room to catch the faint stellar messages written in light from the far reaches of the cosmos is the astronomer whom the telescope operator calls "the star of the Keck." She's not what you think.

Looking too youthful to be a tenured professor, she wears a "lucky sweater" in bright primary colors and munches Oreos and Chips Ahoy -- standard fuel for astronomers facing long, cold nights.

At 33, Andrea Ghez, of the University of California at Los Angeles, already has changed the way astronomers think about star-birth. Now, she has put 25 years of speculation to an end by providing the best evidence yet that a massive black hole sits at the center of the Milky Way. She presented her results at a talk in August at Rutgers University in New Jersey.

Stars as twins

Ghez first shook up the astronomical community with her discovery that most newborn stars appear to be twins. Astronomers have known since the 1970s that roughly half the stars in the universe come in pairs. What was unclear was whether they were born double, or teamed up later in their evolution.

While still a graduate student, Ghez found that the youngest infants in the stellar family are more likely than older stars to be twins. That means, she said, that stars are probably born double.

The discovery has posed a major problem for astronomy because it contradicts the prevalent theories of how stars form. The theories describe a single star condensing out of a glob of interstellar gas. As the gas collapses under the force of gravity, a star is born. Those theories do not provide any good mechanism to explain the formation of double stars.

The theory very nicely produces our sun and planets, Ghez says. "But it only produces single stars. Nature produces doubles. Single stars might be harder to find than we thought."

Her discovery also raises the question of what happens to all the missing partners of the solitary stars like our sun? "That, we don't understand," Ghez says. It is to figure out puzzles of this sort that astronomers come to Keck.

But this sky-high lookout comes with a downside. At 13,800 feet, there's only half the normal supply of oxygen at sea level, and human brains don't function at full speed.

"I don't think as well up here," Ghez says. "If I'm working on the instrument, conversations in the background annoy me. I can't do two things at once."

Astronomers also don't get much sleep. At dawn, they'll drive downhill to their mid-mountain base, turning in for some rest just after breakfast. They wake around 2 p.m., analyze data and get ready for the next night's work. Dinner at 4. Then back to the summit.

Six or more astronomers may spend the night in the Keck control room, communicating with the telescope through computers. Inside, the atmosphere can switch from playful to testy in an instant.

"You put together a diverse group of people," Ghez says. "And if someone [makes you angry], you can't go outside to cool off." Not when the temperature on the summit is well below freezing on the balmiest nights.

Stargazing

As the Earth whirls beneath its sky, different stars come into view. So Ghez comes ready with a laundry list of things to look at.

This night, the astronomers can hardly contain their excitement. One of Keck's two giant eyes focuses on a young star -- called HR 4796 -- with a disk around it that appears to be warped like a phonograph record left out in the sun.

Astronomers have learned during the past decade that many stars are girdled by disks of gas. They theorize that the disks are leftovers from the process of star formation during which the newly igniting star's gravity gobbled up most of the matter in its vicinity. The matter left over in the disks, astronomers think, is the stuff that eventually condenses into planets.

But can planets readily form around double stars? If they cannot, and if lonely stars like our sun are rarities, then how many other solar systems are there?

Ghez thinks a second star in a newly forming solar system might disrupt the disk, thus making planet formation impossible. HR 4796 is in such a double-star system. The fact that the disk around the star is misshapen could be important, the astronomers believe, as evidence that the second star does have an effect on planet formation.

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