CHRISTOPHER PLAIN writes:
University of Montreal (UdeM) researchers have found the first confirmed exoplanets categorized as water worlds. Dubbed Kepler-138c and Kepler-138d, the two ‘super-Earths’ are essentially identical twins, with both about 1.9 times the size of the Earth. Astronomers had previously found an exoplanet they thought may be a water world, but that find still needs to be confirmed by the James Webb Space Telescope (JWST) sometime next year.
Researchers tell The Debrief that more work is needed to fully understand the composition of Kepler-128c and Kepler-138d, and both exoplanets may only contain water vapor and no surface water. However, given that water is the fundamental building block for all life as we know it, the exciting first-ever confirmation of two exoplanet water worlds still dramatically increases the likelihood that alien life exists in the universe.
Note: Water is probably the most common triatomic molecule in the universe; its presence in the composition of planets is not surprising. The claim that the discovery of “two exoplanet water worlds…dramatically increases the likelihood that alien life exists in the universe” is little more than media bait.
WATER WORLDS PREVIOUSLY THEORIZED BUT NOT CONFIRMED
Located in the Lyra constellation, which is about 218 light-years from Earth, the two new planets orbit an M-class (aka red dwarf) star called Kepler-138 or KOL-314. As a result, Kepler-138c and Kepler 138-d are much closer to their host star, with full orbits taking mere days (13.8 and 23.1, respectively) as opposed to the 365.25 days Earth takes to orbit the sun.
“We previously thought that planets that were a bit larger than Earth were big balls of metal and rock, like scaled-up versions of Earth, and that’s why we called them super-Earths,” explained Benneke in a press release announcing the find. “However, we have now shown that these two planets, Kepler-138c, and d, are quite different in nature: a big fraction of their entire volume is likely composed of water.”
In their published paper, which appears in the December 15 edition of Nature Astronomy, the researchers note that Hubble and Spitzer did not directly observe water on the two planets. Instead, their compositions were calculated based on the way they interact with the gravity of the other bodies in the Kepler-138 system. These calculations showed that the twin super-Earths were not as dense as rocky worlds but were denser than helium/hydrogen gas giants like Jupiter. As a result, the best (and likeliest) answer was that both planets contained a significant amount of water, classifying them as water worlds.
BOTH PLANETS MAY CONTAIN A LOT OF VAPOR AND LITTLE TO NO LIQUID WATER
While both Kepler-138c and d are likely swimming in water, so to speak, the researchers caution that most, if not all, of the water on these worlds may not be in liquid form on the surface.
“The water layer is so thick that it extends from the atmosphere all the way into the deep high-pressure interior of the planet,” Paulet told The Debrief. “Therefore, some of the water is in vapor form in the atmosphere while some is in high-pressure water phases such as the “supercritical” phase of water.”
Piaulet told The Debrief that some of the water could theoretically be in liquid form if clouds reflect away enough of the star’s light to cool down the planet a bit, but they’re more likely to expect a “supercritical water ocean” right below the vapor atmosphere. She also noted that pressure typically increases as you move below the surface, so the presence of underground water is even less likely.
“We have reason to believe that there may be more than these two “water worlds” out there, and still have yet to confirm whether what makes for their small density is indeed water or also involves methane or ammonia, which have similar densities as water,” she explained. “This question can only be solved by probing the atmospheres of these planets, indeed using space-based observatories such as JWST!”
Full article at The Debrief.