The gas giant HR 5183 b moves around its star in an inexplicably elongated orbit, then converging very close to it, then moving away for a long time to the distant regions of the system.
“This planet is not similar to any of the planets in the solar system, moreover, it is not similar to any of the known exoplanets,” says one of the authors of the find, an astrophysicist at the California Institute of Technology Sarah Blunt. - Other planets that are so far from their stars have a very small eccentricity, that is, they move in almost even circular orbits. The large eccentricity of this exoplanet indicates some peculiarities in its formation or evolution."
Professor Andrew Howard's team used data from the Lick Observatory in California, W.M. Keck and Texas McDonald's. In the course of a long-term project, scientists have been collecting information on the radial motion of distant stars over the course of decades in order to register exoplanets in distant orbits based on their weak fluctuations, which complete a revolution over tens and hundreds of years.
One of these stars is HR 5183. The orbiting planet, the gas giant HR 5183 b, completes a full circle in its orbit in 45-100 years. The most unusual discovery turned out to be the strong elongation of this orbit: most of the time HR 5183 b spends in its distant limits, gradually slowing down and accelerating, then quickly approach the star and be thrown away again, as if from a giant gravitational sling. If this happened in our system, the planet would converge with the Sun closer to Mars, and then fly away further than Neptune.
In an article published in the Astronomical Journal, scientists note that it was this feature of the orbital motion that made it possible to notice the influence of the attraction of HR 5183 b on its star. Otherwise, such a search method would require observing the complete annual circle of the planet in orbit. Most likely, the high eccentricity was the result of random gravitational interactions with another planet of comparable size.
Having converged and spun, one of them shifted into an unusual orbit, and the other was thrown out of the system. By the way, it is assumed that once our Jupiter also threw out a rather large planet - albeit without such noticeable consequences for itself.