The study of exoplanets is complicated by the fact that the light from their star suppresses the light of the planet itself and makes it difficult to view. But thanks to the technology of the Keck Observatory, it was possible to detect water in the atmosphere of the planet’s star HR 8799 in the constellation Pegasus.
The star itself is a star of the main sequence with an age of 30 million years. In 2008, astronomers announced the observation of three exoplanets around this star – HR 8799b, c and d – with the help of the Keck and Gemini telescopes, and in 2010 they announced the discovery of a fourth planet – HR 8799e.
New observations refer to HR 8799 c – this is a young giant gas planet, seven times the mass of Jupiter, which every 200 years makes a turn around its star. The images obtained confirm the presence of water in its atmosphere and the absence of methane. The results are published in the Astronomical Journal, the lead author of the study is Ji Wang, an associate professor at Ohio State University.
The discovery was made through the use of two technologies of the Keck Observatory telescope. This is an adaptive optics that counteracts the diffuse effects of the Earth’s atmosphere, and a Keck 2 telescope spectrometer, called a Cryogenic Echelle near-infrared spectrophotometer (NIRSPEC), a high-resolution spectrometer that operates in the infrared L-band (type of infrared light with a wavelength of about 3 , 5 micrometers).
HR System 8799 / © Keck Observatory
By combining L-band spectrography with adaptive optics, scientists managed to overcome the difficulties of observing the planet, managing to make the most accurate measurements of the planet and confirming the presence of water and the absence of methane.
“Right now, thanks to the observatory, we can learn about the physics and dynamics of these giant planets, which are not at all like the planets of the solar system. For example, we are now confident that there is no methane on this planet, ”says Van.
Exoplanet HR 8799c is approximately 7 times larger than Jupiter / © Keck Observatory
A team of scientists is already working on the next newest tool in the Keck Observatory, which is called the KPIC (Keck Planet Imager and Characterizer). KPIC will also use adaptive optics and spectroscopy, but with it, astronomers will be able to study planets whose light is even weaker and which are much closer to their star than HR 8799c. Such technology, capable of capturing this planet, will be used on the next telescopes.