U. S. and European space-based X-ray observatories have added a new technique for identifying alien planets with the discovery of HD 189733b, a “hot Jupiter” class world rapidly orbiting a star 63 light years away.
NASA’s Kepler space telescope is credited with making popular a prolific detection strategy based on observations of a slight dimming of the radiance coming from a distant star in optical wavelengths as a planet crosses in front. The search for “exo-planets” got under way two decades ago using subtle wobbles in stellar observations to infer the gravitational influence of an orbiting planet on a host 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.
NASA released Koppenhaeger’s statement as part of an announcement explaining the discovery using NASA’s Chandra X-ray Observatory on Monday.
Chandra was launched in 1999 aboard the shuttle Columbia. The European Space Agency’s XMM Newton, which followed Chandra into orbit in December 1999 aboard an Ariane 5 launcher, provided a confirmation of the first time findings.
The planet HD 189733b is considered the closest hot Jupiter to Earth. The large planet circles its host star once every 2.2 days from an orbital path 30 times closer than the Earth is to the sun.
The star and planet share an intriguing relationship — one that is causing the plentiful atmosphere of 189733b to diminish rapidly. The main star also has a faint red companion star. The companion appears to be much older than the main star, which behaves as though it is 3 to 3 1/2 billion years younger.
“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.”