Extremely Little Telescope makes first planetary discoveries
BY AMANDA DOYLE
Posted: 15 June 2012
An artist's impression of the bloated brown dwarf KELT-1b. Image: Julie Turner, Vanderbilt University.
In the same week that astronomers welcomed the decision to build the European Extremely Large Telescope (E-ELT), the Kilodegree Extremely Little Telescope (KELT) is showing what can be done at the other end of the scale.
KELT is hunting for transiting exoplanets, planets that cause a dip in a star's light as they pass in front, and the first two stellar companions were announced at the meeting of the American Astronomical Society in Alaska this week.
KELT-1b is slightly larger than Jupiter, yet it is 27 times more massive. It has tentatively been classed as a brown dwarf due to its mass. A brown dwarf is a "failed star" that has been unable to initiate the fusion of hydrogen to helium needed to power a star. It is thought that stellar companion between 13 and 80 Jupiter masses signifies a brown dwarf. However there is still much debate about this classification, and much more research is needed to fully understand the formation of brown dwarfs.
Only seven other brown dwarfs have been discovered via the transiting method, and KELT-1b has the shortest period and orbits the brightest star. Its 29-hour orbital period brings it swelteringly close to its stellar host, resulting in the brown dwarf receiving six thousand times more radiation than the Earth receives from the Sun. The intense bombardment of radiation has caused KELT-1b to become inflated beyond the size normally expected. "This is the first definitively inflated brown dwarf we have found," says Scott Gaudi from the KELT team. "Brown dwarf companions are in general rare, so this companion is, in some sense, doubly rare." It is also thought that the radiation might cause the atmosphere of KELT-1b to evaporate quicker than normal, however more calculations are needed to test this idea.
KELT-2Ab is less of an oddity as it is a normal hot Jupiter exoplanet. However it is still a rare find as it transits a particularly bright star, and bright stars are vastly outnumbered by their fainter comrades. The parent star is bright enough that astronomers should be able to observe the atmosphere of KELT-2Ab easily from the ground, as the starlight shines through the planet's atmosphere.
KELT consists of KELT North in Arizona and KELT South in South Africa. The telescopes have been designed to survey bright stars, thus filling a gap in the hunt for transiting exoplanets. "As compared to the other ground based surveys, KELT generally looks at stars about 10 times brighter. Compared to Kepler, our stars are about 100 times brighter," explains Thomas Beatty, lead author of the KELT-2Ab paper. Surveying bright stars also makes the follow-up observations needed to confirm the nature of the transiting objects more feasible.
KELT is currently keeping an eye on around 250,000 stars, and it is thought that up to 10 new exoplanets will be found. "We're also considering looking at new regions of the sky," Beatty tells Astronomy Now. "We have some work underway to allow us to look at extremely bright stars (like things you could see with the naked eye). So I'd say we'll be on the sky for a good while yet!"
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