Profound changes made to view of universe

Press, 29 January 1988, Page 11

Profound changes made to view of universe

By

DAVID CHANDLER

NZPA-KRD Boston The universe just is not what it used to be. At least, it is not what scientists used to think it was. A series of impressive discoveries in the last fewyears has begun to change profoundly astronomers’ views of how the universe formed and how matter is arranged within it. The findings are also yielding significant new information. An astronomer reported he had found what may be the largest assembly of matter ever seen — a huge cluster of clusters of clusters of galaxies, called a supercluster complex. Two teams of astronomers have recently accumulated more evidence, some of it not yet published, for a stilldisputed observation that large numbers of galaxies, including the Milky Way galaxy which contains Earth, are hurtling together across the cosmos toward a region they believe must contain an enormous concentration of matter, dubbed the “great attractor,” whose intense gravitational field is pulling us toward it. If the supercluster complex and the great attractor are real, something that many astronomers still question, they will join the more-accepted finding two years ago of huge empty spaces, or “bubbles,” between the galaxies to present theorists with their biggest headache yet in trying to solve the mystery of how the universe began. “There are really big problems,” said an astronomer, Margaret Geller, of the Harvard-Smithso-nian Centre for Astrophysics, in an interview. There is “a big mismatch between the data and the theory. Things just don’t fit.” Geller is co-discoverer of the empty bubbles in space. The fundamental problem is this: it had been almost universally accepted that, on a large scale, all the objects in space were spread out remarkably smoothly and uniformly and moving in a perfectly predictable, regular way — a steady

expansion. Present theories of how the universe began in a cosmic explosion called the Big Bang require such uniformity, and earlier observations seemed to demonstrate it. No longer. The picture now may be dominated by deviations from that uniformity: the supercluster complexes, which may extend across a sizeable fraction of the cosmos; streaming motions that have entire superclusters of- galaxies hurtling along at more than a million miles an hour; and vast bubbleshaped areas of what appears to be completely empty space, which are hundreds of times larger than a galaxy. “We didn’t really expect to see structures on that scale,” said an astrophysicist, George Field, of the Harvard-Smithsonian Centre. “I think we’re in a revolutionary period.” 4 But while most theorists see the large stuctures as a serious problem, “some people think it can be explained by current theory,” Field said, noting that theorist Mark Davis of the University of California at Berkeley recently gave a lecture titled “No Problems.” Field adds that such views are in the minority, and says of Davis’s title: “Obviously, he’s trying to be provocative. Immediately people got up to challenge his views.” Geller also feels that the problems with existing theory are substantial: “If you took all the observations about large-scale structures, there is no theory that can account for them all. I think people are really scraping the bottom of the barrel trying to make the models fit the data. "I think there is going to be a profound change in the theories,” Geller said. “Something is really wrong with our model ... It may be that a major revision is in order.” Some theories have been proposed that may help to resolve the problems, although none can completely account for all the findings, which could mean some of the new

findings are in error. Among the possibilities Suggested by recent theories are an inflationary universe in which a sudden, rapid expansion during the first moments after the Big Bang introduced great turbulence in the coalescing matter and cosmic strings, “cracks” in the very fabric of the universe which, although infinitesimally small, produce a strong gravitational attraction which may have seeded galaxies and clusters. It is not just by chance that the last few years have produced an explosion of knowledge which challenges mainstream theory about the origins and organisation of the universe. What has happened is that astronomers have gained access to powerful new tools which enable them to probe deeper and in more detail into the depths of space, analysing the light from distant galaxies to glean more accurate information about their distances and motions. Most significant among these new tools have been the products of the revolution in microelectronics, especially light sensors called ' charge-coupled devices, or CCDs, which form the powerful new electronic “eyes” of every thing from new home video cameras to the world’s most powerful telescopes. The surprises in this smaller-scale realm have been less upsetting. Theories are being refined and adjusted in the light of new information, but not overturned. For example, theories of star formation imply that planetary systems should be abundant around the billions of stars in the galaxy, and this conclusion, for which there had been virtually no evidence, has received increasing support. No-one has actually seen a planet orbiting another star, but indirect evidence has been mounting steadily. Most recently, the results of a sixyear project to examine the motions of nearby stars produced by far the

strongest evidence yet that there are large planets orbiting two nearby stars. Astronomers were able to deduce the planets’ existence because they detected that each star had a tell-tale wiggle in its path across the sky; as the planet circled the star, they concluded, its gravitational pull tugged the star first one way, then the other. In addition, clouds of particles ranging in size from fine dust to pebbles have been detected orbiting more than a dozen nearby stars, giving astronomers a direct view of what may be the early stages of the evolution of planets around a new star. The first of these clouds to be photographed, around a nearby star called Beta Pictoris that is visible in Southern Hemisphere skies, also has provided evidence for a strange kind of object that astronomers also think is likely to exist in abundance but has never been seen directly: a brown dwarf, something roughly halfway between a star and a planet. Even harder to see, because they are quite literally shrouded from view, are newborn stars, detection of which would enable astronomers to test their theories of how stars come into being. They are believed to form in dense clouds of gas and dust which gradually form clumps and collapse inward before igniting to become stars, so the process is hidden from view by a smokescreen of dusty matter, rather like raindrops coalescing invisibly inside a dense raincloud. Visible light is useless for penetrating these dense clouds, but the new field of infrared astronomy has finally made it possible to peer into these stellar nurseries. Infrared light, unlike visible light, penetrates easily through dust clouds. One astronomer has described the quest for newborn stars as “the Holy Grail of infrared astronomy.” In 1987, that Holy Grail finally was found,, not once, but in

several places, by teams of astronomers working independently. What had been a sketchy and untested theory has become observed reality. A single one of these newborn stars, Gatley said, has been determined to be as bright as 6 million suns. While the birthing of stars had always been a deeply hidden mystery, astronomers thought they understood relatively well the explosive paroxysms of stellar death — until 1987. In February, for the first time since the invention of the telescope in 1608, a star exploded to become a supernova close enough to Earth to be observed in great detail by astronomers around the world. SN 1987 a, as it is called, flared into view in a galaxy called the large Magellanic cloud which is a satellite of our own Milky Way. It provided scientists with a constant stream of surprises as it stubbornly defied one after another of the predictions of how a supernova is supposed to behave. While the sudden brightening of the star’s light was expected to peak after a few days, it didn’t peak for almost three months; while only red supergiant stars were thought to undergo this type of explosion, this one turned out to have been a blue supergiant — a very different kind of star; and, most surprising of all, a strange companion object was detected, about a tenth as bright as the supernova and apparently very close to it, for which no satisfactory theoretical explanation has been found. The challenges raised by such unexpected and puzzling findings may have the scientists working overtime, but these are the kinds of challenges science thrives on, which lead to breakthroughs in understanding, which keep the work so interesting for those involved.