WM Keck Observatory | California Institute of Technology | 2018 Nov 20
Researchers are perfecting technology to one day look for signs of alien life
Astronomers have gleaned some of the best data yet on the composition of a planet known as HR 8799 c—a young giant gas planet about seven times the mass of Jupiter that orbits its star every 200 years. The team used state-of-the-art instrumentation at the W. M. Keck Observatory to confirm the existence of water in the planet's atmosphere as well as a lack of methane. While other researchers had previously made similar measurements of this planet, these new, more robust data demonstrate the power of combining high-resolution spectroscopy with a technique known as adaptive optics, which corrects for the blurring effect of Earth's atmosphere. ...
Taking pictures of planets that orbit other stars -- exoplanets -- is a formidable task. Light from the host stars far outshines the planets, making them difficult to see. More than a dozen exoplanets have been directly imaged so far, including HR 8799 c and three of its planetary companions. In fact, HR 8799 is the only multiple-planet system to have its picture taken. Once an image is obtained, astronomers can use instruments, called spectrometers, to break apart the planet’s light, like a prism turning sunlight into a rainbow, thereby revealing the fingerprints of chemicals. So far, this strategy has been used to learn about the atmospheres of several giant exoplanets.
The next step is to do the same thing but for smaller planets that are closer to their stars (the closer a planet is to its star and the smaller its size, the harder is it to see). The ultimate goal is to look for chemicals in the atmospheres of Earth-like planets that orbit in the star’s “habitable zone,” including any biosignatures that might indicate life, such as water, oxygen, and methane. ...
Detecting Water in the Atmosphere of HR 8799 c with L-band
High-dispersion Spectroscopy Aided by Adaptive Optics ~ Ji Wang et al
- Astronomical Journal 156(6):272 (Dec 2018) DOI: 10.3847/1538-3881/aae47b
arXiv.org > astro-ph > arXiv:1809.09080 > 24 Sep 2018 (v1), 02 Nov 2018 (v3)