KELT-South is a robotic telescope in South Africa used for astronomy, operated by Vanderbilt University and the South African Astronomical Observatory. KELT stands for Kilodegree Extremely Little Telescope. “Kilodegree” refers to the large area on the sky that the telescope can observe in a single shot. It is a small, low-cost machine that does one thing very well – it monitors the brightness of hundreds of thousands of stars every night, month after month, for many years. The main purpose of KELT-South is to look for specific stars that happen to get a little dimmer on a regular basis, which can be a sign that that the star is being orbited by a planet that passes between us and its star. When that happens, the planet blocks the light from the star from our point of view, causing the star to dim each time the planet makes an orbit. That event is called a transit.
The amount of the dimming in a transit is very small. Even a big gas giant planet like Jupiter that is orbiting a regular star will only block about 1% of the light from the star in a transit. That means that KELT-South needs to be very precise with its measurements. Effectively, every time we measure the brightness of each star, we have to get it right to an accuracy of better than 1% to hope to detect the transit. KELT-South observes about 100,000 stars every time is takes a picture, so our precision has to constantly be exquisite.
KELT-South is fully robotic. It sits in a building in Sutherland, South Africa, and has automated systems to measure the weather. Every night, if the weather is good, the computer opens the roof of the building and the telescope points around the sky, gathering observations of all the stars it sees. The telescope is set up to get the best observations of stars in a particular brightness range, where finding a transiting planet would be especially scientifically valuable. The computer collects the data and transfers it back to Vanderbilt University where it is stored and analyzed.
The picture at the top of this page shows the KELT-South building on the left, with the roof opened and the telescope just about pointing out. For more information about the telescope, the science, and the people involved with the project, see the links at the top of the page.