Trappist-1 is a red-dwarf star, the most common variety, located some 40 light-years away in … [+]
A surprising new study published in Science suggests that many more planets orbiting stars outside of our solar system contain water.
However, that doesn’t mean most are ocean worlds like Earth and nor does it mean they could host life forms. In fact, the study led by the University of Chicago and the Instituto de Astrofísica de Canarias (IAC) suggests that although many more planets may have large amounts of water than previously thought, all of that water is most likely embedded in rock—or possibly in underground oceans.
The research looked at the masses and the radii of all 43 known exoplanets—all smaller than Neptune—around so-called red dwarf stars, which are cooler than our Sun and comprise about 80% of all known stars in our Milky Way galaxy.
The study shows that far more planets than previously thought could have large quantities of water, which can reach up to 50% of the total mass of these exoplanets.
“We have discovered the first experimental proof that there is a population of water worlds and that they are in fact almost as abundant as Earth-like planets”, said Rafael Luque at the University of Chicago and the Instituto de Astrofísica de Andalucía (IAA-CSIC).
That insight comes from a finding about the exoplanets’ densities, specifically that they’re too light to be formed entirely of rock. “We found that it is the density of a planet and not its radius, as was previously thought, which separates dry planets from wet ones,” said Luque. The evidence suggests that these exoplanets must be formed half of rock and half of water or other lighter molecules.
The presence of water on the planet is always presumed to be the first most basic necessity for life elsewhere in the cosmos. That’s why planets with water are always at the top of the list for scientists to further examine in their search for an Earth 2.0.
Artist’s impression of the strange landscape of a water world.
Exoplanets are primarily discovered in two ways.
The first is the transit method. This requires a telescope to be studying a star while a planet transit across its face. It leads to a slight drop in the stars brightness as the planets shadow moves across its face. This transit method also as well as confirming the presence of the planet in the first instance, this transit method also allows scientists to measure the diameter of the planet.
The second method of finding exoplanets is called radial velocity, the measuring of the tiny gravitational pool of the planet exerts on a star. Again, scientists use this data to pinpoint an exoplanet but also to find its mass.
With an exoplanet’s diameter and mass astronomers can begin to unravel information about what they are made of and may look like. Although this is often done for individual exoplanets, this is a rare attempt to describe a population of exoplanets around similar stars.
The 43 exoplanets in question had been presumed to be rocky, but dry. However, this research suggests that water could exist mixed into rock or in pockets under the surface, much like Jupiter’s moon Europa, which is thought to have an underground ocean.
Next up for the researchers is to understand the internal structure of these possible “water worlds,” which means finding out where the water is stored. It’s hoped that one or more of these exoplanets can be proved to be a water world by using the James Webb Space Telescope (JWST), which last week discovered clouds on an exoplanet for the first time.
“It is also fundamental to understand if our discovery also applies to the populations of small planets around other types of stars”, said Luque.
Wishing you clear skies and wide eyes.
