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The super-Earth Kepler-62f orbits a small and cooler star than the Sun at a distance of 1,200 light-years.
Photo: NASA
A planet as large as a super-Earth would disrupt the orbits of most planets, as indicated by a recent study published in the journal Planetary Science. The term “super-Earth” refers to planets larger than Earth but lighter than gas giants. The study’s results show that even small changes in the orbit of Mercury, the largest planet in the system, would have profound effects on the equilibrium orbits of the remaining celestial bodies, as reported by Space on March 13.
Explorations for exoplanets, such as Kepler and NASA’s Transiting Exoplanet Survey Satellite (TESS), have helped astronomers realize that super-Earths are quite common in the Milky Way. Approximately one-third of all known exoplanets are super-Earths. Astronomers argue that our Solar System lacks a super-Earth due to the gravitational influence of Mercury, which prevents its formation by shifting towards the asteroid belt and then returning, thus pushing a considerable amount of material into the Sun.
A super-Earth can be up to ten times the size of Earth. Therefore, Stephen Kane, an astronomer at the University of California, Riverside, and his team simulated planets with varying masses placed at different distances within the main asteroid belt, between Mars and Jupiter. He began with a super-Earth located at twice the distance between Earth and the Sun, or 2 astronomical units (AU, where 1 AU equals approximately 297 million kilometers), and gradually increased the distance beyond the outer edge of the asteroid belt (4 AU or 597 million kilometers). This led to thousands of simulations, each spanning from the present to 10 million years in the future. Every 100 years, Kane recorded the consequences for the eight planets in the Solar System.
According to the simulation results, all four inner planets of the system—Mercury, Venus, Mars, and Earth—were particularly prone to changes in their orbits. In several cases, one or more of these planets could be ejected from the Solar System. None of the thousands of simulations indicated that gas giants like Jupiter or Saturn were expelled. However, in some scenarios, the two gas giants would fling other planets, including newly formed super-Earths or ice giants, out of the system.
When a planet nearly seven times the mass of Earth, such as Gliese 163c, was placed beyond Mars, simulations revealed that the orbits of the four inner planets became unstable. The orbits of Earth and Venus became eccentric, to the point of passing closely by each other. Subsequent changes in the orbit released energy that affected Mercury, causing it to swiftly exit the system. Mars survived for only five million years, while Earth and Venus were ejected after approximately eight million years.
In contrast to rocky planets, gas giants, particularly Jupiter and Saturn, were less affected by the presence of a super-Earth. Their orbits remained slightly unstable only at the Mean Motion Resonances (MMR), where objects with synchronized orbits experience periodic gravitational interactions.
Placing a super-Earth at the far end of the asteroid belt, around 3 AU (447 million kilometers) from the Sun, would cause the least disruption. At this position, it would have minimal interactions with the gas giants.