Artistic vision of a star system with exoplanets
Researchers examining a foreign star system found a pair of planets with strange properties. Their characteristics are so unusual that they may hint at a massive collision in the past.
The main difference concerns the density of worlds. Neighboring planets are similar in size, but one of them is twice as dense as the other. It is believed that such an imbalance is caused by a giant blow that broke off most of the less dense mantle of one of the planets.
We are talking about planets orbiting the star Kepler-107. First discovered in 2014 alongside two other worlds. The two inner planets b and c turned out to be about the same size, so in a new study, scientists tried to determine their massiveness.
Initially, the planets were found using the Kepler space telescope, which tracks small dips in stellar brightness when a planet passes in front of a star. This is a transit method where dips are proportional to the relative parameters of the star and the planet.
But there is another way to search for planets - the radial velocity method, which fixes small oscillations in stellar motion caused by the gravity of the planet. That is, the team could use it to determine the massiveness of the planet. By combining both types of measurements, scientists realized that the two inner worlds of Kepler-107 turned out to be completely different. This system is especially intriguing, because the denser planet lives farther from the star. The reverse situation is usually seen, so researchers have developed several potential mechanisms that can lead a denser planet to an internal system.
But in the specific case, such mechanisms simply do not make sense, because the dense is farther from the star. So scientists suspect that the world of Kepler-107c has become so dense only because of the gigantic blow that destroyed the outer less dense layers.
The scenario seems exotic, but such blows are a common phenomenon in the universe. Even in the Solar System, this could happen with Mercury, Earth, Moon and Uranus (explains its extreme rotation on its side).