218 light-years away, in the constellation Lyra, they inhabit “worlds of water.” They are two exoplanets orbiting a red dwarf star, where water makes up a “large fraction” of the entire planet. The discovery was made by a team led by researchers from the University of Montreal, Canada.
The planetary system is known as Kepler-138 and the research was published in the journal Nature Astronomy. The experts observed the exoplanets Kepler-138 c and Kepler-138 d with the help of the Hubble and Spitzer telescopes and found that the planets may be composed mainly of water.
Water was not directly detected on either Kepler-138 c or Kepler-138 d, but by comparing the dimensions and masses of the planets, the scientists concluded that “a significant part of their volume, up to half, should be made of materials lighter”. than rock, but heavier than hydrogen or helium, which make up most of the gas giant planets like Jupiter.”
“Before, we thought that planets that were slightly larger than Earth were big balls of metal and rock, like shrunken versions of Earth, which is why we called them ‘super-Earths,'” he explained. quoted by NASA in a statementBjörn Benneke, study co-author and professor of astrophysics at the University of Montreal.
“However, we show now that these two planets are of quite different nature and that a large fraction of their total volume is probably made up of water. It is better to prove that the aquatic worlds, a type of planet that was theorized by astronomers, exist long ago.”
And there is one more surprise: Kepler-138 c and Kepler-138 d are “twin” planets, of the same size and mass, contrary to what was thought.
At more than triple the volume and twice the mass of Earth, these now-discovered exoplanets have densities “much lower than Earth.” “This is surprising because most of the planets slightly larger than Earth that have been studied in detail so far appear to be rocky worlds like ours.”
“Imagine larger versions of Europa or Enceladus, the water-rich moons that orbit Jupiter and Saturn but come much closer to their star,” explained Piaulet, study coordinator. “Instead of an icy surface, they would host large envelopes of water vapor.”
According to the researchers, these planets do not have oceans like those on Earth. “The temperature in the atmosphere of Kepler-138 d is probably above the boiling point of water, and we expect a thick, dense atmosphere made of steam on this planet. Only under that steamy atmosphere could there be liquid water at high pressure, or even water in another phase that occurs at high pressures, called supercritical fluid,” Piaulet said.
“As our instruments and techniques become sensitive enough to find and study planets that are farther from their stars, we may start to find many more of these watery worlds,” Benneke concluded.
Source: TSF
