Southern African Large Telescope (SALT) ranks as the largest visible-light telescope in the Southern Hemisphere. SALT’s primary (main) mirror measures an average of 34 feet (10 meters) across. The telescope lies near Sutherland, South Africa, about 175 miles (280 kilometers) northeast of Cape Town. SALT can detect objects a billion times fainter than those that are visible to the unaided eye. Astronomers can use it to study some of the most distant known objects in the universe.
SALT’s primary mirror consists of 91 smaller hexagonal (six-sided) mirrors arranged to form part of a large, spherical bowl. Unlike many other large telescopes, SALT does not tilt its mirror to track a star, galaxy, or other object as it moves across the sky. Instead, instruments at the telescope’s focus move to follow the object. The focus is the place where rays of light meet after being reflected by the mirror. SALT can track an object for a few hours. This design enables SALT to observe about 70 percent of Earth’s southern sky without the complex and expensive machinery needed to tilt the mirror.
SALT is supported by a partnership that includes institutions in South Africa, the United States, Poland, Germany, the United Kingdom, and New Zealand. The telescope opened in 2005.
