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One Photo: 100,000 Galaxies
By Robert Roy Britt
Senior Science Writer
posted: 09:53 am ET
28 December 1999
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many_galaxies_991228While telescopes typically zoom in on a narrow region of sky and turn a pinpoint of light into something dramatic to behold and study, broad surveys of the sky are often the first step in the process of investigation. Such a view, released last week by the European Southern Observatory, contains one of the largest numbers of galaxies ever revealed in a single image. Using the Wide Field Imager at the ESO's La Silla Observatory in Chile, researchers produced the image as part of an effort to create a census of deep space and to gauge the colors and shapes of various distant galaxies, star clusters and other objects. The resulting catalogue helps ferret out which items most warrant further study. The Wide Field Imager is coupled with a 67-million pixel digital camera that records more than 90 percent of all incoming photons from a relatively large patch of sky -- equivalent to the diameter of the Moon as it appears from Earth. ESO researchers said the original high-resolution version of the resulting image, in which 28 exposures were combined, shows 100,000 distant galaxies, in addition to a few foreground stars from our own Milky Way. Researchers said if the sky in every direction is as populous as the patch recorded in this image, then there are some 15,000 million galaxies. And that, they say, would only be the number observable with current technology. Each of the 100,000 galaxies is thought to hold more than 100,000 million stars. Skating across the image is a trail of light left by an artificial satellite that passed through the telescope's field of view during one exposure. Scientists cite the streak as an example of how light pollution affects astronomical observing, even under dark skies in the best possible locations. La Silla sits high atop a mountain bordering the remote southern extremity of Chile's Atacama desert. Such artifacts can be removed by computers, experts say, but always at the loss of some scientific information.
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