Jul 29 2016
From The Space Library
RELEASE 13-237 NASA's Chandra Sees Eclipsing Planet in X-rays for First Time
For the first time since exoplanets, or planets around stars other than the sun, were discovered almost 20 years ago, X-ray observations have detected an exoplanet passing in front of its parent star.
An advantageous alignment of a planet and its parent star in the system HD 189733, which is 63 light-years from Earth, enabled NASA’s Chandra X-ray Observatory and the European Space Agency’s XMM Newton Observatory to observe a dip in X-ray intensity as the planet transited the star.
"Thousands of planet candidates have been seen to transit in only optical light," said Katja Poppenhaeger of Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Mass., who led a new study to be published in the Aug. 10 edition of The Astrophysical Journal. "Finally being able to study one in X-rays is important because it reveals new information about the properties of an exoplanet."
The team used Chandra to observe six transits and data from XMM Newton observations of one.
The planet, known as HD 189733b, is a hot Jupiter, meaning it is similar in size to Jupiter in our solar system but in very close orbit around its star. HD 189733b is more than 30 times closer to its star than Earth is to the sun. It orbits the star once every 2.2 days.
HD 189733b is the closest hot Jupiter to Earth, which makes it a prime target for astronomers who want to learn more about this type of exoplanet and the atmosphere around it. They have used NASA's Kepler space telescope to study it at optical wavelengths, and NASA's Hubble Space Telescope to confirm it is blue in color as a result of the preferential scattering of blue light by silicate particles in its atmosphere.
The study with Chandra and XMM Newton has revealed clues to the size of the planet's atmosphere. The spacecraft saw light decreasing during the transits. The decrease in X-ray light was three times greater than the corresponding decrease in optical light.
"The X-ray data suggest there are extended layers of the planet's atmosphere that are transparent to optical light but opaque to X-rays," said co-author Jurgen Schmitt of Hamburger Sternwarte in Hamburg, Germany. "However, we need more data to confirm this idea."
The researchers also are learning about how the planet and the star can affect one another.
Astronomers have known for about a decade ultraviolet and X-ray radiation from the main star in HD 189733 are evaporating the atmosphere of HD 189733b over time. The authors estimate it is losing 100 million to 600 million kilograms of mass per second. HD 189733b's atmosphere appears to be thinning 25 percent to 65 percent faster than it would be if the planet's atmosphere were smaller.
"The extended atmosphere of this planet makes it a bigger target for high-energy radiation from its star, so more evaporation occurs," said co-author Scott Wolk, also of CfA.
The main star in HD 189733 also has a faint red companion, detected for the first time in X-rays with Chandra. The stars likely formed at the same time, but the main star appears to be 3 billion to 3 1/2 billion years younger than its companion star because it rotates faster, displays higher levels of magnetic activity and is about 30 times brighter in X-rays than its companion.
"This star is not acting its age, and having a big planet as a companion may be the explanation," said Poppenhaeger. "It's possible this hot Jupiter is keeping the star's rotation and magnetic activity high because of tidal forces, making it behave in some ways like a much younger star."
RELEASE 13-225 NASA Welcomes New Chief Scientist
NASA Administrator Charles Bolden has named planetary geologist Ellen Stofan the agency's chief scientist, effective Aug. 25.
Stofan will be Bolden's principal advisor on the agency's science programs and science-related strategic planning and investments.
Prior to her appointment, Stofan was vice president of Proxemy Research in Laytonsville, Md., and honorary professor in the department of Earth sciences at University College London in England.
The appointment marks Stofan's return to NASA. From 1991 through 2000, she held a number of senior scientist positions at NASA's Jet Propulsion Laboratory in Pasadena, Calif., including chief scientist for NASA's New Millennium Program, deputy project scientist for the Magellan Mission to Venus, and experiment scientist for SIR-C, an instrument that provided radar images of Earth on two shuttle flights in 1994.
"Ellen brings an extraordinary range of scientific research knowledge and planetary exploration experience to the chief scientist position," Bolden said. "Her breadth of experience and familiarity with the agency will allow her to hit the ground running. We're fortunate to have her on our team."
Stofan conducts research on the geology of Venus, Mars, Saturn's moon Titan, and Earth. Stofan is an associate member of the Cassini Mission to Saturn Radar Team and a co-investigator on the Mars Express Mission's MARSIS sounder. She also was principal investigator on the Titan Mare Explorer, a proposed mission to send a floating lander to a sea on Titan.
Stofan holds master and doctorate degrees in geological sciences from Brown University in Providence, R.I., and a bachelor's degree from the College of William and Mary in Williamsburg, Va.
She has received many awards and honors, including the Presidential Early Career Award for Scientists and Engineers. Stofan has authored and published numerous professional papers, books and book chapters, and has chaired committees including the National Research Council Inner Planets Panel for the recent Planetary Science Decadal Survey and the Venus Exploration Analysis Group.
RELEASE 13-235 NASA and Korean Space Agency Discuss Space Cooperation
NASA Administrator Charles Bolden and the president of the Korea Aerospace Research Institute (KARI), Seung Jo Kim, met in Washington Monday to discuss collaboration in aeronautics research and space exploration, including KARI's robotic lunar mission and NASA's asteroid initiative.
This was the first meeting between Bolden and Kim.
"Our two agencies share a mutual interest in aeronautics research, and have identified opportunities for collaboration," said Bolden. "We also have partnered for several years in the International Space Exploration Coordination Group and are looking forward to continued discussions on potential cooperation in space exploration."
Bolden and Kim also discussed NASA's plans for a new asteroid initiative, previously announced in President Obama's fiscal year 2014 budget proposal. Kim welcomed the chance to discuss opportunities for collaboration.
NASA's asteroid initiative involves robotically capturing a small near-Earth asteroid and redirecting it safely to a stable lunar orbit where astronauts can explore it.
Capturing and redirecting an asteroid integrates the best of NASA's science, technology and human exploration capabilities and draws on the innovation of America's brightest scientists and engineers. The knowledge gained from the initiative will help us protect our planet, advance exploration capabilities and technologies for human spaceflight, and help us better utilize our space resources.
