A super-Earth may have once formed close to the sun.
Findings of a new study suggest that this young super-Earth formed after clearing up the solid objects that lay between the sun and Mercury. Unfortunately, this primordial world was eventually consumed by the solar system's star after succumbing to its gravity.
Researchers said that a super-Earth could explain why there is nothing seen within Mercury's orbit.
"The only (physical) evidence that super-Earths could have formed in our solar system is the lack of anything in that region, not even a rock," said study researcher Rebecca Martin, from the University of Nevada, Las Vegas.
Super-Earths, which are marked by mass higher than that of Earth's but below that of ice giants Uranus and Neptune, form in two locations.
By observing super-Earths that lie outside the solar system, scientists believe they can form in situ, where they can be seen today, or far from their observed location.
To be formed in situ, super-Earths need to gradually build up from debris in a young planetary system's deadzone called protoplanetary disc, and this would only occur if there is turbulence in the area driven by magnetism of the surrounding materials.
Researchers think that super-Earths formed in situ in the solar system and this swept up all of the materials inside the orbit of Mercury.
Martin and colleagues noted that it is somewhat puzzling that the solar system does not have super-Earths despite the fact that more than half of the exoplanetary systems that have yet been observed have one. The closest super-Earth to our planet, the HD 219134b, is located 21 light-years away.
The fact that there is nothing inside Mercury's orbit, however, may not just be a coincidence as an in situ formation in that region may have cleared the solid materials.
The researchers, however, noted that the super-Earth that formed would eventually have been devoured by the sun given the right conditions.
"This is possible if the active layer surface density is sufficiently large that during the final accretion process there was enough material in the disk for the planets to migrate into the Sun," the researchers wrote in their study to be published in the Astrophysical Journal. "The level of fine-tuning required is certainly possible, but we don't expect it to happen in all systems and this can explain why the solar system is somewhat special in its lack of super-Earths."