Solar System: Newly discovered twin Kepler planets could be unique water worlds
Solar System: Two exoplanets with distinctive compositions that orbit a red dwarf star have been found by astronomers. There have been no other exoplanets discovered outside of the Solar System like these two. There is water in these two worlds.
These water worlds, which are remarkable in that liquid makes up a sizable portion of their makeup, are situated in a planetary system 218 light-years away in the constellation Lyra. The watery discovery was made by astronomers using the Hubble and Spitzer space telescopes to study exoplanets Kepler-138c and Kepler-138d.
The group, led by PhD candidate Caroline Piaulet from the Universite de Montral’s Trottier Institute for Research on Exoplanets (iREx), presented a thorough analysis of the Kepler-138 planetary system.
The planets, which are around 1.5 times the size of the Earth, were found by NASA’s Kepler Space Telescope together with their home star. While water hasn’t been directly observed, scientists have concluded that a sizeable portion of the planets’ volume—up to half of it—should be composed of substances that are lighter than rock but heavier than hydrogen or helium.
Water is the most prevalent of these possible materials.
“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. 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. It is the first time we observe planets that can be confidently identified as water worlds, a type of planet that was theorized by astronomers to exist for a long time,” said Bjrn Benneke, the finding headed by him.
Planets c and d, whose masses are twice as large and whose volumes are more than three times that of Earth, are believed to have substantially lower densities than Earth. This is unexpected considering that the majority of planets that have been thoroughly researched that is only slightly larger than Earth all appeared to be rocky worlds similar to our own.
“Imagine larger versions of Europa or Enceladus, the water-rich moons orbiting Jupiter and Saturn, but brought much closer to their star. Instead of an icy surface, Kepler-138 c and d would harbor large water-vapor envelopes,” explained Piaulet.
Another team from the University of Montreal recently discovered TOI-1452 b, a planet that may have an ocean of liquid water beneath it.