(ORDO NEWS) — The Milky Way Galaxy may be a much wetter place than we thought.
A new analysis of exoplanets orbiting red dwarfs suggests we may have missed out on a population of “water worlds” wet planets. whose composition consists of up to 50 percent water.
Not all of these worlds will be covered by a global liquid ocean; scientists expect that for many of them, water will be associated with hydrated minerals. However, the find may have implications for our search for life outside the solar system.
“It was surprising to see evidence of so many water worlds orbiting the most common type of star in the galaxy,” he says. astronomer Raphael Luque of the University of Chicago.
“This has huge implications for the search for habitable planets.”
While we cannot see any red dwarfs with the naked eye, these stars are incredibly abundant. Small, cool, and dim red dwarfs make up only about half the mass of the Sun at their maximum.
Their low fusion rate gives them the longest lifespan of any star; At 13.8 billion years old, the universe is not old enough for a red dwarf to live its entire life, which is estimated to be 100 billion years.
An estimated 73 percent of the Milky Way’s stellar population is made up of red dwarfs. Just think about it for a moment. When you go stargazing in a cool field or on a truck bed in the desert on a warm summer night, you can’t even see most of the stars in the sky.
Because they are so dim and red, finding exoplanets in orbit around red dwarfs is difficult. Only a small percentage of the 5,084 confirmed exoplanets as of this writing have been found around red dwarfs.
However, our instruments are becoming more sophisticated, so much so that scientists have been able to characterize dozens of small worlds orbiting these small stars.
There are two main signals scientists look at to characterize an exoplanet. The first is the regular faint dimming of starlight as a rotating exoplanet passes between us and the star.
The second is a slight lengthening and shortening of the wavelength of light from the star, as the spinning exoplanet exerts a weak gravitational pull.
If you have these measurements and know how far away a star is (and therefore how much light it emits), you can measure the radius and mass of an exoplanet, two characteristics that astronomers can use to determine the density of an exoplanet.
This density can be used to determine the composition of an exoplanet. Low density probably means an exoplanet with a lot of atmosphere, such as a gas giant. High density probably means a rocky world like Earth, Venus or Mars.
Luc and his colleague, astronomer Enric Palle from the Institute of Astrophysics of the Canary Islands and the University of La Laguna in Spain, conducted a study on the density of 43 exoplanets orbiting red dwarfs.
Generally, these exoplanets fall into two categories: rocky exoplanets and gaseous exoplanets with dense atmospheres. But Luque and Palle saw the emergence of a curious third category: exoplanets that are too dense to be gaseous but not dense enough to be purely rocky.
Their conclusion was that the rock composition of these medium exoplanets was mixed with something lighter… possibly water. But while it’s tempting to imagine a world teeming with rough seas, these planets are too close to their stars to have liquid water on their surface.
If their water were on the surface, it would inflate their atmosphere. , making them even larger in diameter and even smaller in density.
“But we don’t see that in the samples,” says Luke. “This suggests that water does not have the shape of a surface ocean.”
Instead, these worlds may look like another object in the solar system, Jupiter’s moon Ganymede, which is about half rock and half water. with water hidden under a stone ice shell. Or they may look a bit like the Moon (albeit much wetter), with water molecules bound in glass and minerals.
However, these worlds retained their water, if the team’s findings are correct, the discovery suggests that these worlds could not have formed where they formed. Instead, they should have formed further away from their stars, out of rock and ice, and migrated inland to their current positions.
However, without further evidence at this stage it is impossible to decide on the benefit of this model one way or the other.
“Leaving aside this possibility of discovering alien life forms,” writes astronomer Joanna Teske of the Carnegie Institution of Science in a related perspective, “measuring the compositional diversity of planets around red dwarfs the most common type of star in the Milky Way is important in order to piece together a complex the mystery of the formation and evolution of small planets.
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