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50 Light-Years Away : Evidence Hints at a Distant Planet

November 11, 1987|LEE DYE | Times Science Writer

Scientists announced Tuesday that they have discovered evidence of a giant object larger than Jupiter orbiting a star 50 light-years from Earth.

If the finding is confirmed, it would mark the first time that a large, substellar body called a "brown dwarf" has been discovered, although scientists have suspected for years that they abound throughout the universe.

Admitting that his evidence is not conclusive, UCLA astronomer Ben Zuckerman said the "most natural interpretation of our observations is that there is a substellar, somewhat Jupiter-like brown dwarf in orbit around Giclas 29-38," a star that is 300 trillion miles away.

Zuckerman has not actually seen the brown dwarf because no instrument available to scientists today is sensitive enough to photograph such an object, which would be about a billion times dimmer than its nearby star. That would be sort of like trying to pick out the glow of a match alongside a giant searchlight on the other side of town.

But he has determined that more infrared radiation--heat--is being emitted from the immediate vicinity of the star than the star should generate, based on its temperature. That suggests the existence of a companion body that is re-radiating some of the energy from the star, Zuckerman said.

Zuckerman presented his findings to the planetary sciences division of the American Astronomical Society in Pasadena on Tuesday and a full report on his work will appear in this week's Nature magazine, the British science journal.

His presentation Tuesday highlighted discussion of one of the hottest fields in astronomy today, the search for other planetary systems. If planetary systems abound throughout the universe, as a growing number of scientists are concluding, then the chance of life existing elsewhere is greatly enhanced.

Zuckerman has long been known as a critic of those who believe that civilizations exist elsewhere, contending that if extraterrestrial intelligence abounds, so should the evidence, and surely it would have been noticed before now.

But Tuesday, he stopped just short of saying he believes he may have found that evidence himself. He suggested that the heat source around Giclas 29-38 could be the equivalent of giant solar panels created by advanced creatures to harness the power of their sun.

Greeted With Skepticism

His presentation was greeted with some skepticism among the astronomers meeting in Pasadena. Warring factions disagree over which course will most likely lead to proof of other planets, but several scientists familiar with his work said they see no reason to discount his conclusions.

Zuckerman and University of Hawaii astronomer Eric Becklin used the National Aeronautics and Space Administration's three-meter Infrared Telescope Facility at Mauna Kea Observatory in Hawaii for their observations. While studying Giclas 29-38, they detected "excess infrared emissions" that suggested that something else lurked nearby.

For years scientists have been able to predict how much infrared radiation a star should emit based on its temperature, which can be determined through several astronomical methods. The infrared emissions from the area of the star were 2.5% higher than they should be, Zuckerman said, indicating some other source of infrared radiation.

He discounted the suggestion of some scientists that the excess could have come from some galaxy or other faint source in the distant sky directly behind the star. Such a source, which he said would be extremely rare in the universe, would have to be directly behind the star, a coincidence that he said is extremely unlikely.

'Can't Rule That Out'

"We can't rule that out, though," he said. But if the source is from something in the background, "then God is really being cruel to us."

He said it also is unlikely that the source is a huge dust cloud near the star because the history of the star indicates that it went through violent changes 600 million years ago that would have blown the dust away.

So now, he said, he is left with the "most natural" explanation that the source is a Jupiter-like object orbiting the star.

Scientists have long searched for brown dwarfs because they can see no reason why large bodies that are neither stars nor planets should not have formed in much the same way as stars are now known to form. Furthermore, the existence of large bodies that are too dim to be seen would explain a discrepancy in the light-to-mass ratio of the universe. The amount of light suggests there should be more mass, and that has fueled a long search for the "dark matter" that cannot be seen, but would complete the light-to-mass formula.

Other Near Discoveries

The recent history of astronomy is replete with scientists who have thought they had discovered other planets. Many of those discoveries were cast aside when other scientists could not also find them, and in a science where the scale is great and the instruments limited, some discoveries turned out to be minor discrepancies in the data.

That has led many scientists to be skeptical of any reported finding of other planetary systems, although several projects are under way and some astronomers have found evidence that many believe shows disks forming around other stars. Theory suggests that disks should occur in the early phase of planetary formation.

Others have documented "wobbles" in stars that suggest that planet-like objects are orbiting around them.

But no one has won the universal support of the scientific community for discovering other planets outside Earth's solar system. Astronomers meeting in Pasadena on Tuesday made it clear that the jury is still out.

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