This Near-Earth Exoplanet May Be Habitable, But Only Sometimes

when astronomers looking to planets outside Earth for the promise of life as we know it, they look to the habitable zone – a region neither too hot nor too cold for liquid water on the surface. Since there is life virtually wherever there is water on Earth, scientists have focused their searches for extraterrestrial life on habitable planets.

However, a planet’s orbit around a star is rarely a perfect circle, but typically a slightly elongated ellipse. The greater this elongation, or eccentricity, the more a planet can move in and out of its star’s habitable zone.

Now, in a new study accepted in Astronomy and AstrophysicsScientists may have discovered an eccentric planet that regularly enters and exits its star’s habitable zone, posing a challenge to planetary scientists as to what we can and cannot consider habitable.

WHAT DID SCIENTISTS DO? — Astronomers investigated the red dwarf star Gliese 514, located about 25 light-years from Earth. They analyzed data from the Keck Observatory in Hawaii, the La Silla Observatory in Chile, the Calar Alto Observatory in Spain and the Hipparcos, Gaia and TESS satellites, focusing on small oscillations in the star’s position observed over nearly 25 years that can resulted from gravitational tugs from orbiting planets.

A star’s habitable zone depends on the type of star you’re dealing with — and for a planet like Gliese 514 b, it also depends on the time of year. NASA

The researchers found strong evidence that Gliese 514 hosts a “super-Earth”, a rocky planet at least five times the mass of Earth. They suggest that this world, dubbed Gliese 514 b, likely has an eccentric path that takes it outside its star’s habitable zone for two-thirds of its 140-day orbit.

A planet often enters an eccentric orbit due to the gravitational influence of other worlds. Interestingly, “we found no evidence of other planets in the system, especially massive ones, which could be the trigger for the eccentricity of the orbit,” says lead author Mario Damasso, an astrophysicist at the Turin Observatory in Italy. inverse. The origin of Gliese 514 b’s eccentric orbit remains unknown.

WHAT CAN LIFE BE LIKE IN THIS WORLD? — This presents an interesting astrobiological dilemma: did life arise? There’s no way to know for sure without finding biosignatures in the system, which can be difficult. But if life were to arise there, it would be quite unusual.

“I think most actions in terms of biomass growth would happen in the ‘summer,’ and it would have to happen fast, like the Arctic summers on steroids,” Caleb Scharf, director of astrobiology at Columbia University in New York, who did not participate in this research, account inverse.

However, “given how life finds niches, I could imagine other organisms exploiting reduced competition during ‘winter,'” says Scharf. One can even imagine “warm” and “cold” ecosystems, each exploiting the other and each perhaps coming to rest during “winter” and “summer”, respectively, he adds.

Furthermore, such a planet “could be an environment that encourages life in excavations, or life that can insulate when necessary, but get rid of it when it’s ‘summer,'” says Scharf. Furthermore, one can imagine a wide range of photosynthetic life attuned to different levels of light and temperature, he notes.

Naked mole rats are a creature on Earth well adapted to a digging life – something that life on Gliese 514 b would need to survive. image alliance/image alliance/Getty Images

WHAT IS THE NEXT? — “Gliese 514 is a star close to us and could be studied in more detail in the future,” says Damasso. “A follow-up of the system could bring up more precise planetary parameters and likely detect additional lower-mass planets.”

astrophysicist Sean Raymond from the Bordeaux Observatory in France, who was not involved in this study, notes that if there are other planets around this star, they can interact on long timescales, so their eccentricities and inclinations can vary over time.

“The extreme case is a planet whose orbit oscillates between being in a circular orbit within the habitable zone and a very eccentric one that crosses the habitable zone but spends most of its time further away,” says Raymond. inverse. “I can imagine that the types of life that would thrive in each of these environments could be quite different, which would lead to evolutionary pressure favoring adaptability and perhaps long-term hibernation. Too many science fiction stories to be imagined.”

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