New research suggests that at least one super-earth (a planet larger than Earth, but smaller than Neptune) could have formed close to the Sun. Over time, this hypothetical super-Earth would cover up all the rubbish in the area. And due to gravity the sun could eat it.
“This can serve as a possible explanation for why nothing is visible within the orbit of Mercury, although at the moment the evidence is based on modeling and the fact that the area between Mercury and the Sun is so barren,” the authors say.
“The only (physical) evidence that super-lands could have been formed in our solar system is the absence of anything in this region, there’s not even a stone,” said lead author Rebecca Martin, an assistant professor at the University of Nevada, Las Vegas, Email Discovery News. “So they could have formed there, sweeping away all the solid material, but then they landed in the sun.”
The discovery of super-earth exoplanets outside the solar system suggests that they could form in two places: in their place (where you see them today) or away from their observed places, where they would certainly migrate during a long time.
In order to form on the spot, the super-earth will have to gradually build up a mass of debris in the “dead zone”, forming a planetary system known as a protoplanetary disk. This can only happen if there is a sufficiently large amount of turbulence fed by the magnetism of the surrounding material. “The size of the dead zone must be large enough that it has been maintained throughout the life of the disk,” added Martin. “Since different systems may have different sizes of dead zones, formation in the inner parts may not occur in all systems and, thus, both places of formation may function.”
In the super-lands that were observed, the researchers noted two different types depending on their density. They concluded that planets that form further in the disk will be less dense, as water and other volatile substances freeze out into the cold outer parts of the disk. Those that are closer can be more dense.
How are things going in our own solar system? Researchers believe that here super-earths form in place and all the material inside Mercury's orbit is visible. “If the disk is cool enough, the migration of the time scale for them (to fall in the sun) is short enough for it to happen during the life of the disk,” said Martin. But further research is needed to confirm this.