Rebecca G. Martin and Mario Livio at the University of Nevada, Las Vegas, have reviewed essential Kepler Data and suggested that our Solar System may have once had an additional planet – a SUPER-EARTH that perished when it plunged into the Sun. The data collected by the Kepler mission show that what’s missing in our Solar System is a planet, or even rocky debris in the zone between Mercury and the Sun.. In over half of the other solar systems Kepler has observed, Kepler has found planets in the same zone where our Solar System has none.In the early days of our Solar System, the Sun would have formed in the centre of a mass of gas and dust. Eventually, when it gained enough mass, it came to life in a burst of atomic fusion. Surrounding the Sun was a protoplanetary disk of gas and dust, out of which the planets formed. A protoplanetary disk is a rotating circumstellar disk of dense gas and dust surrounding a young newly formed star.
“The lack of Super–Earths in our solar system is somewhat puzzling given that more than half of observed exoplanetary systems contain one. However, the fact that there is nothing inside of Mercury’s orbit may not be a coincidence,” say the authors in the conclusion of their study, and they add that the most likely scenario in our Solar System is the in situ formation of a Super-Earth which subsequently fell into the Sun.
The young solar system would need a dead zone, the depth of the turbulence in the protoplanetary disk would have to be just right, and the disk would have to be the right temperature. The fact that these things have to be within a certain range may explain why we don’t have a Super-Earth in our system, while over half of the systems studied by Kepler do have one.
From their Abstract:
This can help to explain the observed large range in densities of super–Earths because the formation location determines the composition. Furthermore, we speculate that super–Earths could have formed in the inner parts of our solar system and cleared the material in the region inside of Mercury’s orbit. The super–Earths could migrate through the gas disk and fall into the Sun if the disk was sufficiently cool during the final gas disk accretion process. While it is definitely possible to meet all of these requirements, we don’t expect them to occur in all systems, which may explain why the solar system is somewhat special in its lack of super–Earths…
The artist conception shows a newly formed star surrounded by a swirling protoplanetary disk of dust and gas. Debris coalesces to create rocky ‘planetesimals’ that collide and grow to eventually form planets. The results of this study show that small planets form around stars with a wide range of heavy element content suggesting that their existence might be widespread in the galaxy.
Video Credit: University of Copenhagen/Lars Buchhave