A sharp, new eye scans the southern sky.

A sharp, new eye scans the southern sky

Stars in a globular cluster are packed so tightly that ordinary optical telescopes have trouble resolving individual stars. The European Southern Observatory's recently completed New Technology Telescope (NTT) in Cerro La Silla, Chile, has now produced probably the sharpest images of stars in a globular cluster ever obtained using a ground-based telescope. The false-color photograph is a computer-enhanced image of stars near the center of the bright globular cluster Omega Centauri (inset). This cluster, a satellite of the Milky Way galaxy, contains several million stars.

Whereas mirrors in conventional telescopes keep their shape by relying on the thickness of the glass used, the NTT is the world's first telescope for general astronomical use that utilizes "active" optics. Its 3.58-meter mirror is only 24 centimeters thick. Computer-controlled supports pressing against its back maintain the mirror's shape (SN: 3/19/88, p.188). The 10-meter Keck telescope now being constructed on Mauna Kea in Hawaii uses a similar principle.

The NTT saw "first light" on the night of March 23, when the image shown was captured in a 10-second exposure. Because the telescope concentrates light on the detector so effectively, astronomers can see fainter stars than with other telescopes. Depending on the sky background and the accuracy of tracking astronomical objects, even higher resolutions may be possible.