Astronomers have studied the star system found in 2008 by the Observatory W. M. Keck Observatory and Gemini from Hawaii. Star system is called HR 8799 and is 129 light years from Earth. In the star system it is a planetary quartet, all known as super-Jupiter.

As the name suggests, the super-Jupiter planet is greater than Jupiter in our solar system. HR 8799 is famous for this is one of the first planetary systems imitated directly by the telescope. One big mystery about the star system is the rotation period or the rate of round the planets in it. Knowing the rotational rate allows astronomers to know the length of the day on the planet.

The type of data has been measured only for some of the thousands of exoplanets that have been found so far. A group of astronomers have developed instruments called Keck Planet Imager and characterized characters between 2018 and 2020. Instruments can observe exoplanets with very high spectral resolutions. This instrument can provide a high enough resolution to describe how quickly the planet rotates.

This study has shown that the minimum rotation speed for two planets in the HR 8799 star system, known as HR 8799 D and HR 8799 E, rotates at 10.1 kilometers per second and 15 kilometers per second each. The data means that one day length can be as short as three hours or 24 hours on earth, depending on how planets are tilted. Unfortunately, the slope of the planet is not determined at this time.

To compare, Jupiter rotates at 12.7 kilometers per second, and one day on the planet is almost 10 hours. The team can limit the third round of planetary rounds, HR 8799 C, at the upper limit of less than 14 kilometers per second. Unfortunately, researchers cannot determine the level of rotation of the fourth planet in the system, HR 8799 b.