Astronomers Discover Exoplanets Covered by Oceans

Harvard astronomers have discovered two exoplanets in the recently found Kepler-62 planetary system that are covered in endless oceans of water, making them viable candidates for sustaining life.

These water worlds, Kepler-62e and -62f, are 1,200 light years away and are among five planets that orbit the star Kepler-62. Although astronomers do not have telescopes capable of observing these planets directly, they envision Kepler-62e and -62f as worlds entirely submersed in water.

“These two planets are small and orbit around a very distant star,” said Harvard astronomer Dimitar D. Sasselov, who authored the study with Lisa Kaltenegger. “What happens when you have a water planet like that?”

Both astronomers conduct their research with the Harvard-Smithsonian Center for Astrophysics. Their work was published in the Astrophysics Journal last week.

Kepler-62e and -62f are the first water worlds discovered in the “Goldilocks Zone,” a habitable zone of the universe where the temperature is just right to create a sustainable environment for life. The temperature is “not too hot [and] not too cold” because of its distance from the sun, said Sasselov.

The astronomers modeled the terrain of these planets based on observations on their size, their distance from their sun, and their age. The Kepler-62 planetary system is about 7 billion years old.

Based on their model they found that Kepler-62e and -62f are made up of iron core, rock, compressed solid H2O, and a relatively thin surface layer of liquid H2O—a similar composition to that of earth.

“They have not just a little bit of water, but kilometer deep oceans,” said Kaltenegger, who is also affiliated with the Max Planck Institute for Astronomy. These conditions, she said, make them life-friendly, meaning they are potentially capable of sustaining microbes and other organisms.

Both scientists said the discovery of these planets has revitalized the search for habitable water worlds closer to home.

“The next step is finding such planets around stars that are close by,” Kaltenegger said.

If they discover such worlds, scientists say they can use the next generation of telescopes to observe the spectral readings of atmospheric gases and determine whether life exists.

“Life will produce its own gases, oxygen as an example,” Sasselov said. “We want to differentiate the gases due to biology from the gases due to the planet.”

While life could habitat the recently discovered Kepler-62e and -62f, the astronomers said that because they are submerged in water and lack the heavy metals that are within the earth’s crust, it is unlikely the planets could host technology-based life.

Even so, they said it is impossible to know with certainty the habitability of worlds 1,200 light years away.

“We don’t know the inventiveness of what life can do in different circumstances,” she said. “This is all pure speculation.”

—Staff writer Sabrina A. Mohamed can be reached at smohamed@college.harvard.edu. Follow her on Twitter at @sab_mohamed.