Canadian Astronomers Discover Two Amazing Planets That Could Be Made Of Half Water

A team of astronomers has detected evidence that two exoplanets 218 light-years from Earth are "water worlds." The two planets orbit a red dwarf star in the constellation Lyra, unlike any planets in our solar system.

According to a newly published research paper, two exoplanets, which are about one and a half times the size of Earth, could be composed largely of water. The Canadian research team, led by Ph.D. student Caroline Piaulet of the Trottier Institute for Research on Exoplanets (iREx), utilized NASA's Hubble telescope and the retired Spitzer space telescope to make their determinations concerning Kepler-138c and Kepler-138d.

While water was not directly detected, the team concluded by comparing the sizes and masses of the planets to existing models, that a significant fraction of their volume, up to half, should consist of materials that are lighter than rock, but heavier than hydrogen or helium. Water is the most common of the candidate 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," remarked Bjorn Benneke. "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." Benneke added that this is the first time that observed planets can be confidently identified as water worlds, a type of planet that has been theorized to exist by astronomers for a long time.

Until now, most of the planets that are slightly larger than Earth which has been studied in detail seemed to be rocky worlds. Researchers pointed out that the closest comparison to the two planets would be some of the icy moons in our outer solar system, mainly composed of water surrounding a rocky core.

"Imagine larger versions of Europa or Enceladus, the water-rich moons orbiting Jupiter and Saturn, but brought much closer to their star," explained Piaulet. "Instead of an icy surface, Kepler 138 c and d would harbor large water-vapor envelopes."

The team cautions that the planets may not have oceans like those we are familiar with here on Earth. Piaulet says that the temperature in Kepler-138c's and Kepler-138d's atmospheres are most likely above the boiling point of water. The researchers expect a "thick, dense atmosphere made of steam on these planets."

Another surprise the researchers found was that Kepler-138c and Kepler-138d are "twin" planets, with virtually the same size and mass. Before the new findings, the two exoplanets were believed to be drastically different.