Could highly eccentric exoplanets harbor life? “I certainly think it’s a possibility,” said Dr. Tyler Robinson.
When we think about the search for life beyond Earth, especially on exoplanets, we immediately want to search for the next Earth or Earth 2.0. We want exoplanets to orbit their stars in their habitable zone (HZ), with vast oceans of liquid water and lots of land mass around them. There must be life on an exoplanet like this, right? But what if we are in the wrong place? What if we find life on an exoplanet (ie Earth 2.0) that doesn’t have the above characteristics?
This is because some exoplanets have been observed orbiting their parent stars in some rather unbalanced orbits, known as highly eccentric orbits or non-circular orbits. Eccentricity is measured on a scale of 0 to 1, where 0 is a perfectly circular orbit and 1 is an extremely long orbit, where the length of the orbit is much greater than its width. What this also means is that a highly eccentric exoplanet is traveling in and out of the HZ throughout its orbit, which ultimately means this may or may not bode well for finding life on these worlds. After all, could highly eccentric exoplanets harbor life?
“I certainly think it’s a possibility,” said Tyler Robinson, Ph.D., an assistant professor in Northern Arizona University’s Department of Astronomy and Planetary Sciences and an expert on planetary atmospheres and exoplanets. “However, like many other things, the perceived probability that life exists will depend on key details. How strange? How fast does Earth’s day/night cycle spin? The atmosphere and oceans provide some protection against warming and cold events. But if a planet gets too much solar energy, those protections can start to break down.”
In our own solar system, all the planets exhibit approximately circular orbits with eccentricities close to 0, with Earth at around 0.02 and Mercury with the highest eccentricity at 0.2. While eccentricity does not play a role in determining a planet’s habitability, it does play a role in Jupiter’s Galilean moons: Io, Europa, Ganymede, and Callisto, with the first two exhibiting active geology, since Jupiter is responsible for them. pull and stretch constantly. immense gravity due to their slight eccentricities, while also pulling on each other. Since we don’t observe highly eccentric orbits in our own solar system, what can highly eccentric exoplanets teach us about the search for life beyond Earth?
“Exploring the climate of planets in highly eccentric orbits is all about understanding how resilient a planet’s climate is to abrupt changes in energy received at the top of the atmosphere,” said Stephen Kane, Ph.D., professor in planetary astrophysics at UC Riverside. Earth and Planetary Sciences. “While the orbits of the planets in our solar system are largely circular, there are many eccentric orbits in other planetary systems. If these planets could maintain habitable conditions for at least a significant part of their orbits, that could greatly expand the possibilities.” where there is life.”
Dr. Kane is interested in multiple highly eccentric exoplanet systems and says he is a “big fan” of Kepler’s 1649 system. That’s because the system hosts a system similar to that of Earth and Venus, which he says can be used to directly compare it to our own solar system, and was published in the Astrophysical Journal on Kepler in 2021. lead author of a study . -1649. He is also interested in potentially habitable moons orbiting highly eccentric exoplanets, noting that WASP-47c will go in and out of ZH.
Where will we find life beyond Earth? Will we find it on Earth 2.0? Is it a very strange exoplanet, or even one of its moons? Exoplanet systems have shown that very few solar systems mirror our own, so as the search for life beyond Earth continues, so will the places where we might find it.
“Very peculiar exoplanets have the potential to teach us about the importance of cycles in the origin of life,” said Dr. Robinson. “For our planet, it has been suggested that cycles were important to the origin of life: daily warming and cooling cycles, wave cycles on beaches, or monthly tidal cycles. Perhaps, then, more extreme yearly seasonal cycles would help.” to create life. Or maybe not”.