A newly discovered exoplanet with the puffy density of styrofoam may become a testing ground for learning to analyze atmospheres of far-flung planets for signs of life.
KELT-11B, called an exoplanet because it orbits a star outside our solar system, circles a bright star 320 light years from Earth. Its composition and the light it receives make it a prime testbed for scientists to develop tools to examine the types of gases in different planetary atmospheres, expertise that will be necessary in the next 10 years as a new generation of powerful telescopes comes on line.
“It is highly inflated, so that while it's only a fifth as massive as Jupiter, it is nearly 40 percent larger, making it about as dense as styrofoam, with an extraordinarily large atmosphere,” said Joshua Pepper, astronomer and assistant professor of physics at Lehigh University. Pepper led the KELT-11b discovery in collaboration with researchers from Vanderbilt University and Ohio State University, along with researchers at universities and observatories and amateur astronomers around the world.
Several amateur astronomers, called citizen scientists, contributed to the discovery of KELT-11b and are co-authors of the paper. The research was published in The Astronomical Journal [“The Astronomical Journal”.
Like Jupiter or Saturn, KELT-11b is gas planet, but a more extreme version. It resides close to its host star in an orbit that lasts less than five days. Its star, called KELT-11, is depleting its nuclear fuel and evolving into a red giant that will engulf planet KELT-11B in the next hundred million years.
The KELT (Kilodegree Extremely Little Telescope) survey use two small robotic telescopes, one in Arizona and the other in South Africa. The telescopes scan the sky nightly – simultaneously observing tens of thousands of stars once every two-and-one-half minutes – measuring the brightness of about 5 million stars.
In a needle-in-a-haystack process, the large group of professional and amateur researchers search for stars that appear to dim briefly at regular intervals, suggesting that a planet is orbiting that star and eclipsing it. Researchers use other telescopes to measure the gravitational wobble of the star – the slight tug a planet exerts on the star as it orbits – to verify that the dimming, called a transit, is due to a planet, and to measure the planet’s mass.
The KELT survey has discovered 20 planets to date, Pepper said.
Pepper, who began searching for planets beyond the solar system as graduate student in astronomy at Ohio State University, built one of the two modest telescopes used in the KELT survey on a budget of less than $50,000. He now runs the program with researchers at Vanderbilt University, Ohio State University, Fisk University and the South African Astronomical Observatory.
The KELT scientists collaborate with 40 citizen scientists across four continents.
"The KELT project is specifically designed to discover a few scientifically valuable planets orbiting very bright stars, and KELT-11b is a prime example of that," Pepper said.
Exoplanets discovered by the KELT survey will be observed in detail by advanced space telescopes including Hubble and Spitzer and the James Webb Space Telescope, which is scheduled to launch in 2018, to understand how planets form and evolve and how their atmospheres behave, Pepper said.
“We don't know of any real Earth-like planets or stars for which we can measure their atmospheres, though we expect to discover more in future years,” Pepper said. “These [giant gas] planets are the gold standards or testbeds for learning how to measure the atmospheres of planets.”
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