#Qualif
When astronomers used large telescopes to scan the sky for exoplanets, they noticed something strange: worlds of a certain size were clearly missing in space.
Exoplanets come in different sizes. Medium-sized worlds are mostly divided into two groups, known as super-Earths (or super-Earths) and mini-Neptunes (sub-Neptunes). Both are larger than Earth and smaller than Neptune, with super-Earths being 1.75 times the size of our home planet, and mini-Neptunes being four times the size of Earth.
But if the worlds were lined up by size, there would be a noticeable gap between super-Earths and Neptunes, planets about 1.5 to 2 times the size of Earth.
But there is a mysterious gap in these planets, and astronomers believe that the reason behind this is that these planets are shrinking, as they lose their atmosphere, which leaks into space, causing them to become smaller.
The new study found that some of these exoplanets, those larger than Earth but smaller than Neptune, actually push their atmospheres away from the inside through a process known as “core energy mass loss.”
This mechanism is believed to be capable of shrinking a Neptune-like planet down to a super-Earth (a term used to describe rocky exoplanets that are much larger than Earth, but theoretically smaller than gas planets).
Thanks to this information, astronomers say they now have enough data to explain why they don’t see many exoplanets that are about 1.5 to twice the size of Earth. They are planets that fall between the category of super-Earth planets and sub-Neptune planets (smaller in size than Neptune), which fascinates scientists who strive to learn about this phenomenon.
“Exoplanet scientists now have enough data to say this gap is not just a coincidence,” Jesse Christiansen, the study’s lead author and a scientist at Caltech, said in a statement. “There is something preventing planets from reaching and/or staying there.”
The team suspects that this “something” is radiation coming from the depths of these planets smaller than Neptune, specifically their hot cores, which pushes the atmospheres away.
“This radiation pushes the atmosphere from below,” Christiansen added. “An alternative (but unlikely) theory for these subplanets is a phenomenon called photoevaporation, when a planet’s atmosphere is blasted by the radiation of its host star, similar to what would happen if you pointed a hairdryer at an ice cube.” This may not be the answer to this mystery, because this process is believed to occur in the first 100 million years of the planet’s birth, while the new study analyzed sub-planets much older than Neptune.
Christiansen and her colleagues analyzed exoplanet data collected by NASA’s Kepler 2 mission.
