Dark shadows among the galaxies.Dark Shadows Among the Galaxies Has a galaxy been sitting in the dark forbillions of years waiting for a burst of starlight that so far has not come? Or did a new galaxy form as recently as 715 million years ago? Either conclusion could be drawn from the discovery of a dark spiral galaxy by a group of four astronomers from the United States United States, officially United States of America, republic (2005 est. pop. 295,734,000), 3,539,227 sq mi (9,166,598 sq km), North America. The United States is the world's third largest country in population and the fourth largest country in area. and Australia. Either conclusion would be upsetting in one way or another for current theories of the formation and development of galaxies and stars. The object, a gassy gas·sy adj. gas·si·er, gas·si·est 1. Containing or full of gas. 2. Resembling gas. 3. Slang Bombastic; boastful. cloud with a fewfaint stars in it, has the structure of a spiral galaxy, but it is at least 10 times larger and 100 times darker than the average spiral, according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. its discoverers, Greg Bothun of the University of Michigan (body, education) University of Michigan - A large cosmopolitan university in the Midwest USA. Over 50000 students are enrolled at the University of Michigan's three campuses. The students come from 50 states and over 100 foreign countries. in Ann Arbor, Christopher Impey of the University of Arizona's Steward Observatory in Tucson, David Malin of the Anglo-Australian Observatory in Sydney and Jeremy Mould of the California Institute of Technology California Institute of Technology, at Pasadena, Calif.; originally for men, became coeducational in 1970; founded 1891 as Throop Polytechnic Institute; called Throop College of Technology, 1913–20. in Pasadena, who are publishing their results in the June ASTRONOMICAL JOURNAL. Known as Malin 1, the dark galaxy is located in the direction of the famous cluster of galaxies cluster of galaxies Gravitationally bound grouping of galaxies, numbering from the hundreds to the tens of thousands. Large clusters of galaxies often exhibit extensive X-ray emission from intergalactic gas heated to tens of millions of degrees. in the constellation Virgo, but it does not belong to that cluster, and lies in fact some distance beyond it--715 million light-years from earth--in one of the recently discovered voids of space, where few or no galaxies appear to be. Indeed, when first discovered late in1985 as the group was using the United Kingdom Schmidt telescope to survey the Virgo cluster for dark dwarf galaxies, Malin 1 was thought to be part of the cluster. As the most promising dwarf galaxy candidate in the survey, it was singled out for further study. Early in 1986 the 100-inch telescope at the Carnegie Southern Observatory at Las Campanas, Chile, found that it has a bright nucleus and a spiral structure. In May 1986 the 200-inch telescope atMt. Palomar in California determined a redshift redshift Displacement of the spectrum of an astronomical object toward longer wavelengths (visible light shifts toward the red end of the spectrum). In 1929 Edwin Hubble reported that distant galaxies had redshifts proportionate to their distances (see that showed it to be not part of the cluster, but far beyond it. This means that Malin 1 is also much bigger than the observers initially believed. They figure it is at least 770,000 light-years across. The biggest galaxy previously known measures to 640,000 light-years across. In work done with the radiotelescope at Arecibo, Puerto Rico, scientists have now verified the distance and determined the mass of the hydrogen in Malin 1, which they report is at least 100 billion times the mass of the sun. Malin 1 thus has plenty of the materialout of which stars form. The most widely accepted theory holds that all the galaxies formed in a short period near the beginning of the universe 10 billion to 20 billion years ago. If Malin 1 formed then, why didn't star formation turn on? On the other hand, Malin 1 could be new as we see it 715 million years ago. As Impey says, "It's not unreasonable to theorize the·o·rize v. the·o·rized, the·o·riz·ing, the·o·riz·es v.intr. To formulate theories or a theory; speculate. v.tr. To propose a theory about. that spiral galaxies might be forming now, in other words Adv. 1. in other words - otherwise stated; "in other words, we are broke" put differently , very close to us.' Photo: In normal photo (right) Malin 1 looks like a dwarf member of the Virgo cluster. Enhanced contrast (left) shows it as much less dwarfish. |
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