Water worlds common in red dwarfs? Can.

larger view. | This is an artistic depiction of extrasolar planet TOI-1452 b. It is slightly larger than land and may be completely covered in the depths of the ocean. Spins around one of 2 small red dwarf stars It is located in the constellation of Draco about 100 . light years from Earth. Astronomy scientists announce It was discovered last month (August 2022). Now, a new study says that water worlds may be common around such stars. Image via Benoit Gougeon/Institute for Research on Exoplanets/ University of Montreal.

The Earth is a water world, with its vast oceans, lakes and rivers. Elsewhere in our solar system, other bodies have subterranean water oceans, including Jupiter’s moon Europa And the moon of Saturn Enceladus. But are there watery worlds the outside Our solar system? Mounting evidence suggests that it is. In fact, a new study by researchers at the University of Chicago says that water worlds – at least one type of them – may be common around red dwarf stars. However, most of this water is probably underground. Researchers published they Peer review The results are in the journal Sciences On September 8, 2022.

Water worlds revolve around red dwarfs

The new study focuses on red dwarf stars, the most common type of star in our galaxy. a lot of outer planets Planets outside our solar system So far, astronomers have discovered red dwarf stars in their orbit. The researchers wanted to look at the constellations of planets orbiting these stars. These worlds include rocky, water-rich, and gas-rich planets. Their examination indicates that water worlds are likely to be common among those planets. Raphael Locklead author of the new study, He said in UChicago News:

It was surprising to see evidence of so many watery worlds orbiting the most common type of star in the galaxy. It has dire consequences for the search for habitable planets.

2 different monitoring techniques

The researchers found clues regarding the size and mass of the planets by combining two different methods of observation. one called transit method, based on the transit of a planet in front of its star, as seen from our point of view on Earth. the other is Radial velocity method, where a very small gravitational pull of a planet on a star is measured by a telescope. By combining the results, scientists get a better idea of ​​the size and mass of the planets. Co-author Enrique Ballet From the Institute of Astrophysics of the Canary Islands and the University of Laguna said:

The two different ways of discovering planets give you different information.

Earth is on the right side with 6 smaller moons next to it, with white text on a starry background.
larger view. | Earth is just one of the many watery worlds in our solar system. This illustration depicts the many moons of the outer solar system, along with Earth, which are now known to have subterranean oceans. image via Woods Hole Oceanographic Institution.

Half rock, half ice

Scientists assumed that most of these planets would be rocky, like Earth. And they are… kind of. However, the results suggest that it is probably more like half rock and half water. This is because the measured densities of the planets indicate that they are too light to be pure rocks. as such Jacob Ben At the University of Chicago he said:

I was shocked when I saw this analysis. I and a lot of people in the field have assumed that these are all dry, rocky planets.

There is a catch though. The results suggest that although the planets contain a lot of water, it is more likely to mix with rocks, or in pockets below the surface, rather than drift on the surface. why? Because these particular planets orbit near their stars. Any surface water, if it did not boil away, would be present in the supercritical gas phase. In this case, this will make the apparent radius of the planet appear larger. But this is not what astronomers have noticed. As Loki noted:

But we don’t see it in the samples. This indicates that the water is not in the form of a surface ocean.

Water worlds similar to Europe?

If this scenario were true, and these planets contained most or all of the water found underground, it could make them more similar to Europa or other ocean moons in our solar system. On those moons, liquid water is under the surface crust of the ice, but the measurement is similar. For Europe specifically, there is not only the subterranean ocean, but there is also increasing evidence of it pockets of water Lakes, if you will – within the icy crust itself.

Man wearing glasses, mustache and beard.
Raphael Lock at the University of Chicago led the new study on the worlds of water around them red dwarf stars. image via University of Chicago.

Formation of the outer planets

The findings also have implications for how planets form. They support the theory that many planets actually form away from their stars and then gradually migrate inward. These once cooler planets could eventually reside in the region closest to their star where liquid water would be possible. as such pointed in paper:

Formation models that include orbital migration can explain the observations: rocky planets form inside the snow line, while water-rich worlds form outside and later migrate inland.

A white planet-like sphere with many dark curved lines on its surface.
Jupiter’s moon Europa is the most famous oceanic world, excluding Earth, in our solar system. This image of Europe is composed of Galileo A spacecraft, made from images acquired in 1995 and 1998. Do you see the many crisscrossing cracks and ridges covering Europa’s surface? It gives the moon the appearance of a cracked egg. Image via NASA/ Jet Propulsion Laboratory – California Institute of Technology/ City Institute.

Other aquatic worlds

In another study from July 2022, scientists He said who – which Super Earth thick outer planets primitive The atmosphere can also be habitable water worlds.

Last month (August 2022) scholars announce The discovery of an extrasolar planet 100 above the Earth light years Far away it may be completely covered in water. From the studies and discoveries that are being made, it appears that there may be a variety of water worlds present in our galaxy. Exciting prospect!

Bottom line: Scientists at the University of Chicago say rocky water worlds are likely common around red dwarf stars. Most of this water is likely underground, but not at the surface like the oceans.

Source: Density, not radius, separates rocky, water-rich minor planets orbiting dwarf stars M

Source (preprint): Density, not radius, separates rocky, water-rich minor planets orbiting M dwarf stars

Via University of Chicago