Search for life on very eccentric exoplanets

(ORDO NEWS) — When we think about looking for life beyond Earth, especially on exoplanets, we immediately want to look for Earth 2.0: an exoplanet that orbits a star in the habitable zone, with vast oceans of liquid water and lots of land.

But what if we find life on exoplanets that don’t have the aforementioned characteristics?

Some exoplanets orbit their parent stars in very eccentric orbits. Eccentricity is measured from 0 to 1, with 0 being a perfectly round orbit and 1 being an extremely elongated orbit that is much longer than wide.

This means that such an exoplanet can move in and out of the habitable zone throughout its entire orbit. Given these circumstances, could very eccentric exoplanets potentially harbor life?

“I certainly think it’s possible,” said Dr. Tyler Robinson, who is an assistant professor of astronomy and planetary science at Northern Arizona University.

“But, as with many other things, the estimated probability of saving a life will depend on key details. How eccentric is she? How fast does the planet rotate during its day/night cycle?

The atmosphere and oceans provide some buffer against warming and cooling, but this protection can begin to break down if the planet receives too much energy from its star.”

Within our solar system, all the planets have mostly circular orbits with an eccentricity close to 0, while for the Earth it is 0.02. Since we don’t see highly eccentric orbits in the solar system, what can highly eccentric exoplanets teach us about the search for life beyond Earth?

“Investigating the climate of planets with highly eccentric orbits is all that is needed to understand the resilience of the planetary climate to abrupt changes in the energy received in the upper atmosphere,” said Dr. Stephen Cain, Professor of Planetary Astrophysics in the Department of Earth and Planetary Systems Sciences at the University of California in Riverside.

“Although the orbits of the planets in the solar system are mostly circular, there are many eccentric orbits in other planetary systems.

If these planets can maintain habitable conditions in at least most of their orbits, then this could greatly expand the number of places where life is possible.

“Very eccentric exoplanets have the potential to tell us about the importance of cycling in the origin of life,” Dr. Robinson said.

“With regard to our Earth, some have suggested that cycles were important to the origin of life the daily cycles of heating and cooling, the cycles of waves on a beach, or the monthly cycle of tides.

Perhaps then the more extreme annual cycle of the seasons could have helped to give rise to life. Or maybe not”.

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