Astronomers at California State University at San Francisco have discovered an exoplanet with a bizarre elongated orbit that is typical of comets.
The planet, named HD 20782, has an orbital eccentricity of 0.96, which means that its trajectory around the star is a flattened ellipse. Only some comets are more eccentric. However, HD 20782 is very different from a comet because it is comparable in mass to Jupiter.
At the farthest point in its orbit, the exoplanet is 2.5 times farther from the star than the Earth is from the Sun. In this case, the planet periodically approaches the hot surface of the star - much closer than Mercury to the Sun. A year on this planet lasts 597 days.
HD 20782 is 117 light years distant from the solar system. It was discovered using the transitive method, which consists in observing the passage of planets against the background of a star's disk. Despite the great distance, scientists managed to record a flash of light reflected from the exoplanet's atmosphere during its passage at a close distance from the parent star. Astronomers plan to study the spectral characteristics of the reflected radiation to determine the composition and structure of the atmosphere of the distant world.
Scientists explain the strange orbit of HD 20782 by the fact that initially there could be several planets with unstable orbits in the system. At some point, they came too close to each other, due to which one of them flew out of the system, while the other acquired its elongated orbit.
Earlier, astronomers discovered an exoplanet with an orbit farthest from the star, which is seven thousand times farther than the distance from the Earth to the Sun. In total, as of March 17, 2016, 1,988 exoplanets were discovered.
