(ORDO NEWS) — Planetary scientists at Northern Arizona University and the University of California, Riverside are studying exoplanets with highly elongated orbits.
Scientists believe that even if the planet’s orbit goes beyond the habitable zone, life can still arise on such a planet.
We are accustomed to thinking that life needs conditions the same as on Earth. But apparently it’s not necessary.
When we think about the search for life beyond Earth, especially on distant exoplanets, we first of all want to find the “next Earth”.
We hopefully look for an exoplanet that orbits a star in a habitable zone (HOZ) with vast oceans of liquid water and lots of land. That is, so that everything is like on our home planet.
There must be life on such a planet. But such planets, apparently, are quite few. But will we find life on exoplanets that do not have such Earth-like characteristics, that is, on Earth 2.0?
For example, we already know exoplanets that revolve around their parent stars not in circular, but in highly elongated orbits or, as scientists say, orbits with a large eccentricity.
The eccentricity is measured from 0 to 1, where 0 is a perfectly round orbit, and the closer it is to 1, the more elongated the orbit (the eccentricity is exactly 1 – it will be already at the parabola, planets cannot rotate around stars in such orbits).
An exoplanet with a large eccentricity passes through the OZ, but exits it. Of course, such an exit from the OZ does not mean anything good for life. But planetary scientists wondered: could life exist on exoplanets with large eccentricities?
Life on exoplanets
“I think that life on planets with large eccentricities is possible,” says Dr. Tyler Robinson, assistant professor of astronomy and planetary science at Northern Arizona University. “But the perceived likelihood of life would depend on a number of key details. How elongated is the orbit?
How fast does the planet rotate on its axis? Are its atmosphere and oceans powerful enough, and can they provide a buffer against heating and cooling? And there are many other factors that can influence the possibility of the emergence of life.”
In the solar system, almost all planets have circular orbits with an eccentricity close to 0, and for the Earth it is about 0.02. Only Mercury has a significantly elongated orbit, it has the highest eccentricity of 0.2. But exoplanets with elongated orbits have already been found a lot.
“Studying the climate of planets with large eccentricities is about understanding the resilience of the planetary climate to abrupt changes in the flow of energy received by the upper atmosphere,” says Dr. Stephen Cain, professor of planetary astrophysics at the University of California at Riverside.
“If these planets can maintain habitable conditions in most of their orbits, this could greatly expand the places where life is possible.”
Dr. Kane is investigating, in particular, the high-eccentric exoplanet WASP-47c, which orbits both inside and outside the OZ.
Stephen Cain says that the discovery of exoplanets has already shown that very few planetary systems are similar to the Sun, but this does not mean that there is certainly no life there.
“Exoplanets with large eccentricities can teach us a lot,” said Dr. Robinson. “Maybe a more extreme annual cycle could even help the origin of life. But maybe not.”
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