A Sutherland robotic telescope spots an extrasolar planet

18 May 2016
A Sutherland robotic telescope spots an extrasolar planet

A Sutherland based robotic telescope KELT-South spotted an extrasolar planet KELT-10b during its routine observations. KELT-South (Kilodegree Extremely Little Telescope – South) is dedicated to the search of transiting planets orbiting especially bright stars.

Astronomers refer to these planets as “hot Jupiters” because of their composition and mass. They are gas giants similar to the planet Jupiter, except that they orbit extremely close to their host stars. The planet, KELT-10b, has a mass 30% less than Jupiter but is 40% larger in radius, which makes it very inflated. It orbits its host star about once every 4.2 days. According to calculations, KELT-10b has a surface temperature of about 1100 degrees Celsius – Jupiter has a surface temperature of about -145 degrees Celsius. KELT-10b’s host star is slightly hotter and larger than the sun. Although it is too dim to see with the naked eye, it is visible with a small telescope.

KELT-10b is especially interesting because of its very strong transit signal and a fairly bright host star. Those two properties make it such a valuable target for further investigation, to learn about the composition of its atmosphere, how heat is transferred from its star to the lower gas layers, and around to the back side of the planet through the winds.

According to the South African Astronomical Observatory (SAAO) based astronomer, Dr. Rudi Kuhn the process of finding these planets is quite involved, “There are numerous objects that appear to have the same characteristics as transiting planets but turn out to be something else. Careful, meticulous investigation is therefore required to identify real transiting planets. Thus, astronomers have to use separate methods for identifying and confirming possible transiting planets. Initial discoveries are made using the transiting technique, which determines the amount of light blocked by the planet when it moves in front of the star. The method used to confirm whether it is a transiting planet is the radial velocity or ‘wobble’ method, which measures the wavelength of light received from a star as it is tugged by the gravity of its planet.”

American based collaborator, Dr. Joshua Pepper says the discovery of KELT-10b is important because, “The goal of this search is to find transiting planets orbiting especially bright stars, as they are excellent targets for follow-up observations with big telescopes like the Southern African Large Telescope (SALT) to measure their atmospheres.” Since the discovery of 51 Pegasi in 1992 many more extrasolar planets have been detected. Before the discovery of 51 Pegasi, astronomers had believed that other planetary systems would have to be like ours, with small rocky planets close to the parent star and massive gaseous planets further out.

Ground-based surveys for extrasolar planets have become more successful, with their number reaching 130 so far. These surveys use small aperture wide-field robotic telescopes to obtain high-precision photometric light curves of relatively bright stars.

The Kilodegree Extremely Little Telescope (KELT) project deployed KELT-South to Sutherland in 2008 while Dr. Rudi Kuhn was busy with his Masters degree at the University of Cape Town. He developed the computer software that controls the telescope, which means the telescope can observe on its own, without an astronomer physically operating it. “Being involved in the construction of the telescope was the fulfilment of a childhood dream, enabling me to bring together my interest in both astronomy and computer programming” says Dr. Kuhn.


(1) The robotic KELT-South telescope in Sutherland.
(2) Light curve of KELT-10b's host star. The dip in intensity is caused when the planet is moving in front of the star, blocking out some of the latter's light.


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