HD 158259, the almost perfect star system

An international team of astronomers has solved some of the mysteries surrounding HD 158259 . We now know that this star system located 88 light years away is made up of six planets with almost perfect orbital resonance.

The universe of astronomy is currently in full swing. And for good reason, an international group of scientists led by astronomer Nathan Hara of the University of Geneva in Switzerland has unveiled new information about a star system located in the constellation Dragon. Since the advent of modern astronomy, scientists have spotted hundreds of star systems scattered across the galaxy, but HD 158259 is proving to be one of a kind. Its star has a mass almost identical to that of the Sun and is slightly larger in terms of diameter. As Science Alert reports , HD 158259 includes six planets: a super-Earth and five mini-Neptunes.

HD 158259, the almost perfect star system

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After spending seven years studying this star using the SOPHIE spectrograph and the TESS space telescope, astronomers now know much more about it.

An orbital resonance considered extraordinary

Between 2011 and 2019, HD 158259 was the subject of more than 250 measurements using the equipment mentioned above. Measurements that have allowed astronomers to see that the six known planets that orbit the star have an almost perfect orbital resonance. Orbital resonance is defined as a situation in which the orbits of two celestial bodies around a common barycenter are closely related, as the two bodies exert a gravitational influence on each other.

Orbital resonances known in the solar system occur for example at the level of the satellites of Jupiter which are Io, Europa and Ganymede as well as at the level of those of Saturn, among others, Mimas and Tethys, Enceladus and Dione, Titan and Hyperion. Orbital resonances have also been observed in the HD 158259 star system. Each planet orbiting the star resonates at a roughly 3: 2 ratio with the next planet farther away, with a period ratio of 1.5.

An important discovery

According to the researchers, the discovery of this way in which the planets of HD 158259 interact with each other is not trivial. Since they now know that the planets of the star system are in near-perfect orbital resonance, astronomers should be able to better understand the mechanisms of formation of the star system.

“With these values on the one hand, and the tidal effect models on the other hand, we could focus on the internal structure of the planets in a future study. In summary, the current state of the system gives us a window into its formation, ” said Nathan Hara.

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