A new study opens the door to hundreds of millions of habitable exoplanets

In a recent study published in Proceedings of the National Academy of Sciencesa pair of researchers from the University of Florida (UF) examined the orbital eccentricities for exoplanets orbiting red dwarf stars (M dwarfs) and determined that a third of them, which includes hundreds of millions in the entire Milky Way , could exist within the habitable zone of their stars. (HZ), which is the approximate distance from their star where surface liquid water can exist.

Researchers have determined that the remaining two-thirds of exoplanets orbiting red dwarfs are too hot for liquid water to exist on their surfaces due to extreme tides, resulting in sterilization of the planetary surface.

I think this finding is really important for the next decade of exoplanet research because eyes are turning to this population of stars, said Sheila Sagear, who is a doctoral student at UF and lead author of the study. These stars are excellent targets for looking for small planets in an orbit where it is conceivable that the water could be liquid and therefore the planet could be habitable.

For the study, Sagear and her consultant, Dr. Sarah Ballard, analyzed the orbital eccentricities of 163 exoplanets orbiting red dwarf stars in 101 systems using data from NASA’s Kepler mission. For context, red dwarfs are roughly the size of Jupiter, so they are much smaller than our Sun. This smaller size means that red dwarfs emit much less energy and heat than our Sun, which means that the HZ exists much closer to the star, resulting in shorter orbital periods for planets orbiting within the HZ.

The orbital eccentricity of a planetary body refers to the shape of its orbit. While Earth’s orbit is almost perfectly circular, astronomers have discovered planetary bodies both inside and outside our Solar System to exhibit more eccentric or oval-shaped orbits. Eccentric orbits can cause huge fluctuations within planetary bodies, regardless of their size. One such example within our Solar System is Jupiter’s moon Io, whose eccentric orbit turns out to be the most volcanically active body in our Solar System.

During its orbit, Io is constantly stretched and compressed by gravitational interactions with Jupiter as its distance changes, sometimes approaching and moving away from Jupiter at other times. Over large amounts of geologic time, Io’s interior heats up due to friction produced within it, leading to the heat and volcanic activity we observe to this day. This process is known as tidal heating, which is what this most recent study explores with exoplanets.

Ultimately, Saeger and Dr. Ballard found that red dwarf stars that possess the most exoplanets had the highest promise of exhibiting more circular orbits, just like Earth, meaning they could harbor liquid water on their surfaces. In contrast, the researchers found that red dwarf dwarfs boasting only one exoplanet were more likely to exhibit a higher eccentricity orbit, resulting in them experiencing tidal extremes, just like Jupiter Io, and less likely to harbor water. liquid on its surface.

While the study found that only a third of exoplanets in the 163-sample size could contain liquid water on their surfaces, that also means there are potentially hundreds of millions of such worlds in the Milky Way alone.


Launched in 2009, NASA’s Kepler mission has been instrumental in expanding our understanding of exoplanets and the likelihood of their habitability. During its 9-year mission that ended in 2018 after its fuel ran out, Kepler confirmed the existence of nearly 2,800 exoplanets, with nearly 2,000 potentially still awaiting confirmation, known as exoplanet candidates. While this most recent study included a small slice of those confirmed exoplanets, Kepler’s data will no doubt keep scientists busy for years to come.

What new discoveries will scientists make about M dwarfs, their exoplanets and their characteristics? Only time will tell, and that’s why we use science!

As always, keep doing the science and keep looking up!

This article was originally posted on Universe Today by Lorenzo Tognetti. Read the original article here.

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