A super Earth and five Neptunes!
Scientists have discovered a six-planet system — a “super-Earth” and five “mini-Neptunes” which display an exceptionally regular spacing, hinting at how the system may have formed. The planets revolving the star HD 158259 in the Draco constellation were found using the SOPHIE spectrograph installed at the Haute-Provence Observatory in the South of France.
The observations showed that the planet that is closest to HD 158259 and the five outer planets present masses of two and six times that of the Earth, respectively. The system has been found to be compact, in the sense that the distance of the outermost planet to its star is 2.6 times smaller than the distance between Mercury and the Sun.
But its most interesting feature is its regularity. The period ratio of any two subsequent planets is close to 3:2. This means that as the first planet — the one closest to the star — completes three orbits, the second one completes about two. As this second planet completes three orbits, the third completes about two, and so on.
NASA’s TESS space telescope observed a decrease of the star’s brightness as the innermost planet transited between the observer and the star.
Unlike other worlds, Uranus is tilted so far that it essentially orbits the sun on its side, with the axis of its spin nearly pointing at the star. Many astronomers believe this unusual orientation might be due to a collision with an Earth-sized planet soon after it was formed.