This Mysterious Planet Could Be Transforming Into a Water World - ScienceAlert

An analysis of an exoplanet named HD-207496b reveals that the world, clocking in at 6.1 and 2.25 times the mass and radius of Earth, respectively, either has a gaseous atmosphere, a global ocean, or a mixture of both – and it could be shrinking down to become a super-Earth.

And one interesting thing we've learned is that there is a glaring scarcity of exoplanets between 1.5 and 2 times the mass of Earth with orbits shorter than around 100 days.

The reasons for the valley aren't entirely clear, but a growing body of evidence is beginning to suggest that close proximity to the host star has something to do with it.

It's possible that below a certain critical threshold, an exoplanet just doesn't have enough mass to keep a gravitational grip on its atmosphere (the gas is evaporated by the star's radiation).

If the star's brightness is known, the depth of the transit dips – how much starlight is blocked – allows astronomers to calculate the radius of the orbiting body.

"We find that HD-207496b has a density lower than Earth, and hence we expect that it has a significant amount of water and/or gas in its composition," the researchers write in their paper.