Study Explores Two Earth-Like Exoplanets Revealing They’re More Like Earth Than Previously Believed

The weather on exoplanets Kepler-186f and Kepler-62f may be a lot like what we're experiencing here on Earth, thanks to their stable axial tilt.

Earth-like exoplanet Kepler-186f, the first confirmed Earth-size planet in the habitable zone of a distant star.
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The weather on exoplanets Kepler-186f and Kepler-62f may be a lot like what we're experiencing here on Earth, thanks to their stable axial tilt.

Earth-like exoplanets Kepler-186f and Kepler-62f are known for, well, their close similarity with our home planet. But a new study recently published in The Astronomical Journal disclosed that the two exoplanets, both orbiting within the habitable zone of their host stars, are actually more like Earth than we ever knew.

The research, conducted by scientists at the Georgia Institute of Technology (Georgia Tech) in Atlanta, examined the axial tilt of these two exoplanets and uncovered that it is very stable, just like Earth’s, Phys.org reports.

This discovery is a huge revelation in terms of these exoplanets’ likelihood of being habitable, because it points to a stable climate with regular seasons.

What We Know About Kepler-186f And Kepler-62f So Far

You may have heard about Kepler-186f (pictured above) a few years back, when it was first discovered in the data collected by NASA’s Kepler space telescope. Hailed as a massive breakthrough, Kepler-186f is the first confirmed Earth-sized planet to orbit a distant star in its habitable zone and is often referred to as “Earth’s cousin,” the Inquisitr previously reported.

Found in 2014, Kepler-186f is part of a five-planet star system located 500 light-years away from our planet, in the Cygnus constellation (the “Swan”), notes the Daily Mail. The exoplanet has a radius 10 percent larger than that of Earth and orbits its parent star — a red dwarf cooler than our sun, notes Space.com — every 130 days.

Of the five planets revolving around this distant red dwarf, Kepler-186f is the fifth and outermost, and scientists believe it’s most likely rocky.

Meanwhile, Kepler-62f resides even further away, in the Lyra constellation, at a distance of 1,200 light-years from us. Just like Kepler-186f, this exoplanet also belongs to a five-planet system and is the farthest one from its host star.

Discovered in 2013, Kepler-62f held the title of the most Earth-like exoplanet for about a year, until Kepler-186f was detected. This giant exoplanet is 40 percent larger than Earth and has a good chance of being a rocky world, possibly covered by oceans.

Both these exoplanets are found in the “Goldilocks zone,” or habitable region, of their respective stars, meaning that their distance from the parent star is just right for the surface temperature to allow the build-up of liquid water.

Earth-Like Climate

The recent study shows that, aside from all these traits, which make Kepler-186f and Kepler-62f good candidates for hosting life, the two Earth-like exoplanets also have an Earth-like climate.

This further increases the chances that alien life could evolve on these planets, study lead author Gongjie Li said in a Georgia Tech news release.

“Our study is among the first to investigate climate stability of exoplanets and adds to the growing understanding of these potentially habitable nearby worlds,” stated Li, who is an assistant professor of physics at the university.

Li’s team ran computer simulations to gauge the spin axis dynamics of both exoplanets and found out how much they tilt on their axes and how their tilt angles change over time.

Since axial tilt affects how much sunlight reaches a planet’s surface, these measurements are highly important in establishing what kind of climate we might expect to find on Kepler-186f and Kepler-62f.

According to the results, both exoplanets seem to have stable, Earth-like climates due to their stable axial tilt, which is very similar to that of our own planet.

Phys.org notes that Earth’s axial tilt has a mild oscillation once every 10,000 years and ranges between 22.1 and 24.5 degrees. Meanwhile, our planetary neighbor Mars has a “very unstable” axial tilt, which varies from zero to 60 degrees, Li points out.

“That instability probably contributed to the decay of the Martian atmosphere and the evaporation of surface water,” said the physicist.

While Mars doesn’t have a large enough natural satellite to stabilize its axial tilt, our moon “keeps Earth’s variations in check,” preventing our planet’s axial tilt from oscillating too much under the influence of the strong interaction between Earth and Mars, notes Georgia Tech.

“It appears that both exoplanets are very different from Mars and the Earth because they have a weaker connection with their sibling planets,” says Li.

“We don’t know whether they possess moons, but our calculations show that even without satellites, the spin axes of Kepler-186f and 62f would have remained constant over tens of millions of years.”

While there’s a possibility that life could also thrive on planets with irregular seasons, a stable climate could mean a better chance for alien life to spark on the two Earth-like exoplanets.

As Li puts it, “a climatically stable planet might be a more comfortable place to start.”