Habitable Exoplanets May Have Chaotic Climate Change Impacts Caused by Sister Planets

The hunt for life continues as telescopes become more powerful as technology improves. But knowing exactly where to look is half the battle. Now, scientists have described possible planetary systems where a gravitational nudge from one planet with just the right orbital configuration could have a devastating impact on the orbit and climate of another, possibly habitable world.

It's all about gravity. The orbit of a planet is a primary driver of climate, which means that whether or note life can exist on a planet largely depends on orbit. When one planet impacts another planet's orbit, it's called a "mean motion resonance." More specifically, this occurs when two planets' orbital periods are an integer ratio of each other; for example, this is seen with Neptune and Pluto when Neptune orbits the sun three times for every time Pluto orbits twice. A repetitive force happens at the same place in the planets' orbits around the star, and the effect of this grows slowly over millions of years.

Why does this matter? This can happen to a planet that's orbiting in a star's habitable zone. This, in turn means that scientists should probably give these planets low priority when searching for life.

"What happens when you have planets that are in this resonance and with mutual inclinations?" said Rory Barnes, one of the researchers, in a news release. "And what we found was that things go all haywire. Those little perturbations that keep happening at the same point cause one of the orbits to do some crazy things-even flip over entirely-and then kind of come back to where it was before. It was pretty unexpected for us. Planets in systems that drive orbits to near-misses with the host stars are less promising targets that should be skipped over for other candidates, even if they are found today on circular orbits in the habitable zone."

The findings narrow done where scientists should search for life. This, in turn, may make it easier to eventually track down life outside our solar system.

The findings are published in the Astrophysical Journal.

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