Wednesday, June 7, 2023

Water is abundant on many minor planets

Artist's impression of an aquatic world, where half of its mass is in the form of water. (photo: pilar montanes - @pilar. Monro (iac))

Artist’s impression of an aquatic world, where half of its mass is in the form of water. (Photo: Pilar Montanes – @pilar.monro (IAC))

Artist’s impression of an aquatic world, where half of its mass is in the form of water. (Photo: Pilar Montanes – @pilar.monro (IAC))

Water is present in abundance on many small extrasolar planets, but it does not flow into oceans and rivers as it does on Earth, but is probably embedded in rock or in pockets below the surface, led by the University of Chicago and Spanish According to a study in the Institute of Astrophysics (IAC) of the Canary Islands.

A study published this Thursday in the journal science And this suggests that there are abundant populations of water and rock exoplanets around M-dwarf stars, which are most common in the Milky Way.

For this study, a detailed analysis was conducted, led by researchers Rafael Luk from the University of Chicago and the Institute of Astrophysics of Andalusia (IAA-CSIC) and Enrique Paley of the IAC and the University of La Laguna (ULL). of the radius and mass of 43 known small exoplanets around M dwarf stars, which represent 80% of the stars in the Milky Way.

Raphael Luc explains in a statement that he discovered the first experimental evidence that aquatic worlds exist as a population, and that, in fact, they are almost as abundant as the terrestrial planets.

According to the study, planets may contain large amounts of water, which may account for up to 50% of the planet’s total mass, than previously thought.

Enrique Palle told Efe that half of these planets are water, so the amount is much larger and if it were in the form of an ocean it would be thousands of kilometers deep, but the data indicate that the topmost layer has melted and water. Down and up to the core.

He said that, at some point, there will be liquid water and it is not known whether there is life, but it is known that a large number of planets are equal to Earth, so the chances of finding life are greatly increased because of this..

When the researchers analyzed the samples they found something unexpected, as the density of a large percentage of the planets suggested they were very light relative to their size to be made of rock alone.

Therefore, they believe that these planets must be composed of half rock and half water or some other lighter molecule, and they have found that it is the density of the planet and not the radius, as previously thought, that makes up the planets. separates. Wet, Raphael Luk commented.

However, these planets are so close to their suns that any surface water would exist in a supercritical gas phase, increasing their size.

Therefore, scientists believe that in this type of population, water would probably end up in rock or in pockets below the surface, rather than flowing like oceans or rivers.

These conditions would be similar to those of Jupiter’s moon Europa, but very different from those occurring on Earth, which is a “dry” planet, despite the fact that almost all of its water is on its surface, giving it a very dry appearance. , Earth’s water is only 0.02% of its total mass, while in the aquatic world it is 50% of the planet’s mass”, explained Enrique Paley.

“Aquatic World”

In addition, he found that minor planets around these stars can be described by discrete populations of families: Earth-like planets, 50% of their mass is composed of water (water worlds or “water worlds”).water World“) and mini-Neptunes with extended atmospheres of hydrogen and/or helium.

This discovery contradicts the general idea that these worlds are either dry and rocky or have an extensive and thin atmosphere of hydrogen and/or helium.

And it suggests, instead, that unlike rocky planets, these water-rich worlds formed outside the so-called “snow line,” which is at a distance where temperatures were low enough for lighter compounds such as water to freeze. and forms solid ice grains, later migrating inwards.

The distribution of the size and density of exoplanets is a direct result of the formation of planets at different distances from the star, Palle remarked, not the presence or absence of an atmosphere.

The researchers point out that, just as observing the population of an entire city can reveal trends that are difficult to see individually, studying planetary populations has helped to identify patterns hitherto unknown.

“Due to errors in the mass and radius of our measurements, an individual planet can sometimes fit into different categories (terrestrial,”water World“…) It is only when we observe planetary populations, as we do here, that patterns of different composition can be resolved”, explained Luke.

According to the researchers, the next step will be to understand the internal structure of the water world, that is, where water is stored, and whether these planets may host a small detectable supercritical water vapor atmosphere.

Enrique Palle states that only planets around M stars in the habitable zone are accessible for atmospheric exploration by the James Webb Space Telescope (JWST) and the Very Large Ground-based Telescope in the future.

“It is also essential to understand whether our finding applies to populations of minor planets around other types of stars”, Luke explained. And he stresses that the precise masses of smaller planets around massive stars are more difficult to obtain, but may soon be provided by state-of-the-art ultrastable spectrographs.

New discoveries of planets around M dwarf stars made by NASA’s Transiting Exoplanet Survey Satellite (TESS) mission, as well as mass determinations made by the Carmenus spectrograph installed 3.5 meters from Calar Alto in Almería, were part of this work. were necessary for.

This article was originally published on The HuffPost and has been updated.

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