An unusual giant telescope has taken its first photographs of the night sky from its perch in the mountains of the Karoo region of South Africa.
The Southern African Large Telescope (SALT) is the largest single-aperture telescope in the southern hemisphere, with a 10 by 11-metre segmented mirror. Although the European Southern Observatory鈥檚 (ESO) Very Large Telescope (VLT) has a larger total area it consists of four separate eight-metre telescopes.
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SALT uses a simple design pioneered by the Hobby-Eberly Telescope at the University of Texas, which meant the government-owned South African Astronomical Observatory could build it for a mere $18 million.
The telescope鈥檚 main mirror, made of 91 hexagonal segments, is tilted at a fixed angle to the ground. The mirror sits on a platform parallel to the ground that can be swivelled to aim starlight gathered by the telescope toward a movable overhead tracker and digital camera. The design avoids the huge cost incurred by using precision machinery to aim the mirror itself at any point in the night sky.
Learning curve
The telescope was the first of its kind, and 鈥渉as struggled a bit to get up to doing routine science鈥�, says SALT scientist Eric Wilcots, of the University of Wisconsin in Madison, US. But SALT has benefited from the experience. 鈥淵ou learn a lot when you鈥檙e second,鈥� Wilcots told 快猫短视频. 鈥淲e will have our own birthing pain, but will be able to avoid worse problems.鈥�
SALT鈥檚 first results are images of important objects in the southern sky 鈥� a galaxy, a nebula, and several star clusters. However, the main advantage of such a big ground-based telescope is the ability to collect enough light to analyse the spectra of faint objects.
The southern sky includes a particularly rich section of the Milky Way, and the two brightest satellites of our galaxy, the Magellanic Clouds. Later in September, Wilcots鈥檚 group will install an imaging spectrograph in order to record the spectra of thousands of individual stars in the Magellanic Clouds. Tracing their histories in this way could give insight into the evolution of other galaxies.
The observatory is not as high as ESO鈥檚 VLT site in Chile but, as it is far from any cities, Wilcots says it has 鈥渂eautifully dark skies鈥� that should be very good for spectroscopy.
