Tidal locking of exoplanets – planets like Earth orbiting a star, but outside the solar system – could be more common than previously thought. Which is big news in the search for life out there.
It means many exoplanets still to be discovered are likely to have one side permanently facing their host stars, according to new research by astronomer Rory Barnes of the University of Washington.
NASA explained that tidally-locked planets are held in place by their star in the same way the Earth holds the moon.
“One side of a tidally-locked planet always faces its star, and one side always faces away,” experts noted.
“That gives one-half of the planet a sunny day side, and the other half a lasting starry night.”
A University of Washington report detailing Barnes’ findings suggested that NASA’s Transiting Exoplanet Survey Satellite (TESS) was likely to discover potentially habitable planets were also tidally locked.
“The possibility of tidal locking is an old idea, but nobody had ever gone through it systematically,” Barnes said.
Researchers previously modeled exoplanet behavior on 12-hour estimations of the Earth’s rotation period.
Barnes expanded these parameters for this study, saying the rotation of a planet could be longer than several hours, even weeks.
“When you explore that range, what you find is that there’s a possibility for a lot more exoplanets to be tidally locked,’ he said.
“For example, if Earth formed with no moon and with an initial ‘day’ that was four days long, one model predicts Earth would be tidally locked to the sun by now.”
What Barnes discovered was that the process of tidal locking could feature as a prominent factor when it came to the evolution of potentially habitable exoplanets yet to be discovered.
“I think the biggest implication going forward is that as we search for life on any exoplanets we need to know if a planet is tidally locked or not,” Barnes said.