Virgo images suggest smaller universe.

For the first time, astronomers have distinguished individual stars in a galaxy in the Virgo cluster and measured their distance from Earth. Observations of the galaxy NGC 4571, made with a new high-resolution camera, support the notion that objects in the universe may lie about half as far away as previously thought. If so, the cosmos as a whole may be smaller than believed.

Robert D. McClure of the Dominion Astrophysical Observatory in Victoria, British Columbia, and his colleagues conducted their study at the Canada-France-Hawaii Telescope on Hawaii's Mauna Kea. They photographed NGC 4571, obtaining sharp enough resolution to distinguish bright individual stars from groups of fainter stars. By comparing the brightness of the luminous stars with that of Milky Way stars in the same class and at a known distance from Earth, they deduced that NGC 4571 lies 50 million light-years from Earth.

Because astronomers often use the distance to Virgo as a yardstick for assessing the distance of objects farther out in the universe, the new finding indicates that such objects may lie much closer to Earth, McClure says. Since an object's distance serves as an indicator of its age, a smaller cosmos would seem to suggest that the universe is younger than the estimated 10 to 20 billion years. On the other hand, scientists have clearly established an age of 15 billion years for some ancient star groups in the Milky Way.

The high-resolution camera attached to the Mauna Kea telescope uses adaptive optics to correct for the image-distorting effects of Earth's atmosphere (SN: 6/8/91, p.358), yielding an image about five times as sharp as those produced by most other ground-based telescopes, McClure says.