Two scientists from the University of Nevada Las Vegas have suggested the existence of at least one super-Earth in the early days of the solar system located within the orbit of planet Mercury which ended up being devoured by the Sun.

The region of space in our solar system between the Sun and Mercury is now barren, not even a rock is seen there. Scientists have long wondered about this “nothingness” and now they may have solved the mystery. In the new study accepted for publication in the Astrophysical Journal astronomers explain that a super-earth, planet larger than Earth but smaller than Neptune, may be the responsible agent in clearing out the vast empty space within the orbit of planet Mercury.

Over time, this hypothetical super-Earth must have formed near to the Sun sucking up all the debris in the area before plunging into the Sun and meeting a fiery death.

The only evidence that super-Earths could have formed in our solar system is the lack of anything in that region, not even a rock,

said Rebecca Martin, an assistant professor at the University of Nevada.

So they could have formed there sweeping up all of the solid material, but then later fell into the sun.

Scientists based their hypothesis on observations made Nasa’s Kepler space telescope. Kepler’ data showed that super-Earth exoplanets formed in either of the two locations: in situ (in the position where they are currently seen) or far out from the host star and then migrate inwards.

Based on the current cosmological models, if these planets form in situ, would have to slowly build up from debris in the “dead zone” of a forming planetary system, known as a protoplanetary disc. This is a possibility only in the presence of extreme turbulence caused by magnetism of the surrounding materials.

The size of the dead zone must be large enough that it lasts for the entire disc lifetime,

Martin added.

Since different systems may have different dead zone sizes, formation in the inner parts may not be possible in all systems and thus both formation locations may be operating.

According to the authors of the study, at least one super-Earths formed in place and accreted the material inside of Mercury’s orbit, orbiting the sun around 10-100 million years after the solar system formed 4.6 billion years ago. Then the planet migrate towards the sun before finally being devoured by our star.

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.

Dr Livio added: The lack of super–Earths in our solar system is somewhat puzzling given that more than half of observed exoplanetary systems contain one.