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Using adaptive optics to compensate for atmospheric turbulence, astronomers at WM's Keck Observatory at the top of Maunakea, Hawaii, confirmed the presence of water and lack of methane in the atmosphere. A planet known as the 8799c HR, gas giant about seven times more massive than Jupiter and taking 200 years to perform an orbit of its star host.
Other researchers have made similar observations, but Keck's observations show the interest of combining adaptive optics and high-resolution spectroscopy, the researchers say. The long-term goal is to enable the necessary technologies to determine the chemical composition of the exoplanet atmospheres and to detect possible biosignatures in the atmospheres of Earth-like planets.
"This type of technology is exactly what we want to use in the future to look for signs of life on a planet similar to Earth," said Dimitri Mawet, an associate professor of astronomy at Caltech and a researcher at Jet Propulsion Laboratory of NASA. "We have not arrived yet but we are moving forward."
HR 8799 is located approximately 130 light-years from Earth in the constellation Pegasus. The star has about 1.5 times the mass of the sun and almost five times its brightness. It has four known planets and is the only multi-planet system of this type to be directly imaged.
For the new HR 8799c study, the Keck II telescope and cryogenic cryogenic scale spectrograph, or NIRSPEC, in the near infrared, combined with Keck's powerful Adaptive Optics System to mitigate atmospheric blur.
The observations marked the first use of this technique to directly image an exoplanet in the L-band, ie an infrared light with a wavelength of about 3, 5 micrometers.
"The L band has been largely neglected before because the sky is brighter at this wavelength," Mawet said. "If you were an alien with your eyes fixed on the L-band, you would see an extremely bright sky. It is difficult to see the exoplanets through this veil. "
The use of adaptive optics has made the L-band more accessible, allowing researchers to accurately measure the atmospheric constituents of the HR 8799c, thereby confirming the presence of water, as it is previously believed. They were also able to confirm the absence of methane.
Mawet and his colleagues are developing a new instrument called Keck Planet Imager and Characterizer, or KPIC. He will also use adaptive optics and high-resolution spectroscopy to study planets that are fainter than HR 8799c and position themselves in an orbit closer to their host stars.
"KPIC is a stepping stone for our future thirty-meter telescope instrument," said Mawet. "For the moment, we are learning a lot about the countless ways in which the planets of our universe are formed."
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