Photo credit: NASA
Science Recorder | Stephanie Verkoeyen | Tuesday, July 30, 2013
Planets outside our solar system, commonly referred to as exoplanets, were discovered almost 20 years ago. Now, for the first time, X-ray observations have detected an exoplanet passing in front of its parent star.
The advantageous alignment occurred in the HD 189733 system, 63 light-years from Earth. As the planet transited its star, both NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM Newton Observatory observed a dip in X-ray intensity.
Katja Poppenhaeger of Harvard led the study, which is to be published in The Astrophysical Journal next month. According to Poppenhaeger, thousands of planets have been detected in optical light, but being able to study one in X-rays reveals new information about its properties.
The planet, known as HD 189733b, is similar in size to Jupiter, but is in very close orbit around its star, a condition referred to as a “hot Jupiter.” HD 189733b is the closest hot Jupiter to Earth, making it a prime target for astronomers. NASA’s Kepler space telescope has been used to study it at optical wavelengths, while NASA’s Hubble Space Telescope has confirmed it is blue in color.
In this new study, clues have been revealed regarding the size of the planet’s atmosphere. During the transits, the spacecraft observed a decrease in light. X-ray light experienced a decrease three times greater than did optical light, which suggests that there may be extended layers of the planet’s atmosphere transparent to optical light, but opaque to X-rays.
“However, we need more data to confirm this idea,” said co-author Jurgen Schmitt.
Researchers are also learning how the planet and the star can affect one another. For a decade, astronomers have known that ultraviolet and X-ray radiation has been evaporating the atmosphere of HD 189733b over time, losing an estimated 100 million to 600 million kilograms of mass per second.
The planet’s extended atmosphere has made it a larger target for high-energy radiation, with its atmosphere thinning about 25 percent to 65 percent faster than if the atmosphere were smaller.
Chandra’s X-rays also detected a faint red companion to the main star in HD 189733. Though likely formed at the same time, the main star appears to be at least 3 billion years younger than its companion due to a higher rotation. The main star also has displayed higher levels of magnetic activity, and is about 30 times brighter in X-rays than its companion.
This unusual activity may result from having a big planet as a companion, according to Poppenhaeger. The hot Jupiter may be keeping the star’s rotation and magnetic activity high as a result of tidal forces, making it behave like a much younger star.
Earlier this month, it was announced that HD 189733b is a true blue planet.
“We saw the light becoming less bright in the blue but not in the green or red. Light was missing in the blue but not in the red when it was hidden,” said Frederic Pont of the University of Exeter. “This means that the object that disappeared was blue.”
Not only is HD 189733b a blue planet, it may rain glass on this alien world.
Read more: http://www.sciencerecorder.com/news/nasa-spots-eclipsing-planet-in-x-rays-for-first-time/#ixzz2aXWpAfDm
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