Harvard astronomers last week cautioned against concluding too much, let alone the existence of a second solar system or new life forms, from the announcement last Wednesday that a satellite had detected solid particles circling a nearby star.
While they acknowledged the discovery as an important confirmation of long-standing suspicions that solid material exists outside the sun's family of nine planets, the experts said that evidence to support further claims--as some reports have--is largely circumstantial.
"What they have is fairly significant, but it's definitely not the smoking gun for a planetary system," said David Layzer, Menzel Professor of Astrophysics. "There's not even an indication that there are solid objects larger than a pinhead."
Officials at NASA's Jet Propulsion Laboratory (JPL), which made the announcement Wednesday, have said that the particles recently detected around the star Vega--one of the sky's brightest--could range in size anywhere from buckshot pellets to asteroids or large planets.
Scientists remains unsure about the exact nature of the find because it was made with an infrared satellite, which uses non-visual detectors to search for sources of radiation that are relatively cool, in comparison to the hot, gaseous stars that comprise the majority of know celestial objects.
Despite the lack of a visual siting, however, the detection has gained unusual attention because it represents the first positive astronomical measurement of solid material in deep space larger than dust grains or gas partices, which are unable to sustain the type of orbital activity now suspected around Vega.
The objects in question are thought to be of the same type that were left in the area of the sun after its formation, and that eventually came together to form the earth and other planets.
"The available evidence may suggest for or against the presence of a major planetary system around Vega, and is intriguing in its own right. But the issue as to whether there are planets is not easily resolved," said Professor of Astronomy Alastair G. W. Cameron.
Cameron, Layzer, and other Harvard experts raised questions about the discovery based largely on the imprecision of the initial announcement. In fact, several said that other issues left some lingering doubts about the accuracy of the find in the first place.
"It sounds like a very exciting report, but I'm a bit skeptical about what they're seeing at this early stage," said Jonathan E. Grindlay, professor of Astronomy. Grindlay noted that several of his colleagues discussed what they believed to be a discrepancy between scanning ability of the satellite involved and the degree of accuracy needed by last week's discovery.
Based on press accounts of the find, Grindlay estimated that the "angular resolution" of the Infrared Astronomy Satellite--operated jointly by the U.S., Britain, and the Netherlands--was too great to accurately detect the kind of readings that the circling cloud of particles might induce.
Officials at JPL downplayed such concerns, saying they were certain of the existence of solid objects, even without being sure of their size, shape, or mass. But, according to Charles Beichman '73, a senior scientist at JPL, the concerns expressed by Grindlay and others may not have been entirely speculative.
The reading was "just at the borderline of what we can resolve," Beichman said. He added that JPL scientists were jubilant at the find, even though it has been anticipated within the scientific community for years.
"There's a large list of eminent astronomers who are now kicking themselves because they had the information and never followed up," said Beichman, who explained that while Vega is a star commonly used by astronomers as a sort of "space lighthouse" for calibrating visual instruments, data from countless other stars--about 250,000 in JPL's computers alone--has been gathered for various purposes other than the type of infrared examination that led to the latest find.
While scientists at JPL and elsewhere are now reviewing past data in search of further confirmation of the Vega particles at least one Harvard scientist is planning on taking a more direct look--through some ground-based telescopes based in Hawaii. Giovanni G. Facio, lecturer on Astronomy, said that he planned to use a trip to an observatory on the Pacific Island this past weekend to see if he could visually site the particles, which he said might resemble the rings around Saturn.