Saturday , October 23 2021

They detect water in the atmosphere HR 8799 c, the planet 179 light years from Earth


GIF: HR 8799 with planets orbiting (Jason Wang Data analysis)

A team of astronomers at the Keck Observatory has detected water in the planet's atmosphere a few light years away from us. Your name: HR 8799 c.

Actually, at that distance there is a solar system next to the star HR 8799 and the planet HR 8799 b, c, d, and e. Several years ago, in 2008, scientists announced that they had directly observed three exoplanets around stars: HR 8799 b, c and d, using the Keck and Gemini telescopes. Then, in 2010, they announced the discovery of the fourth planet, HR 8799 e.

However, the study now presented is based on previous work in 2008. The new observation was HR 8799 c, observed for the first time that year. A young giant gas planet, about 7 times the mass of Jupiter, which orbits its star every 200 years.

New observations with direct images have confirmed the presence of water in the atmosphere and the lack of methane. For this, a team of astronomers used a powerful combination of two telescope technologies at Beck.

Image: The HR 8799 system contains the first exoplanet where the image will be taken directly (NRC-HIA / C. MAROIS / W. M. KECK OBSERVATORY)

The first is what is called adaptive optics, which counteracts the diffuse effects of Earth's atmosphere. The second is a spectrometer at the Keck 2 telescope called Echelle Near Infrared Cryogenic Spectrograph (NIRSPEC), a high-resolution spectrometer that works with infrared light. According to Dimitri Mawet, professor at Caltech:

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. We are not there yet, but we are moving forward.

So far, astronomers have directly photographed more than a dozen extrasolar planets. The HR 8799 system is the first multi-planet system to get images directly. However, these images are only the first step in this study. Once taken they can be analyzed for chemical composition in their atmosphere. And this is where spectroscopy comes in. In this case, the NIRSPEC skill is the key.

Image: The exoplanet HR 8799c is approximately 7 times the size of Jupiter (W. M. KECK OBSERVATORY / ADAM MAKARENKO / C. ALVAREZ)

NIRSPEC is an instrument that operates in the L infrared band. This is a type of infrared light with a wavelength of about 3.5 micrometers and a spectrum region with large detailed chemical traces. According to Mawet:

The L band has been ignored before because the sky is brighter at this wavelength. If you are an extraterrestrial with eyes that are in harmony with the L band, you will see a very bright sky. It's hard to see exoplanets through this veil.

By combining bands with adaptive optics, they are able to make the most accurate planetary measurements, thus confirming the presence of water and the absence of methane. [Universe Today]

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