Astronomers for the first time measured the duration of the day on exoplanets in the HR 8799 system, located in 129 light years from the ground. The planetary system, found in 2008, consists of four super-jupiters – gas giants, which are an order of magnitude a massive of Jupiter in the solar system. The results of the study are published in the form of preprint in the repository ARXIV.ORG.
Measurements were performed using the Keck Planet ImageRer and Characterizer (KPIC) tool, which is able to distinguish the spectra with close wavelengths, that is, it has a resolution sufficient to determine the speed of rotation of the planets. It turned out that the speed for HR 8799 D and HR 8799 E constitute 10.1 kilometers per second and 15 kilometers per second, respectively. This means that the duration of the day can be 3-24 hours, as on Earth, depending on the slope of the planets, which is currently not defined. For context, Jupiter has speed of rotation of about 12.7 kilometers per second, and one day on Jupiter lasts almost 10 hours.
Scientists were also able to determine the upper limit of the rotational speed of the third planet HR 8799 C, equal to 14 kilometers per second. The speed of rotation of the fourth planet, HR 8799 B, can not be finally defined.
Earlier it was reported that the astronomers of the European South Observatory (ESO) first discovered the disk around the planet, which is the first stage of satellite formation. The octoplane disk surrounded by an exoplanet PDS 70C type gas giant, which is located at a distance of 400 light years from the ground.