Super-Earths Are More Common Than We Thought, Study Reveals

Using the Korea Microlensing Telescope Network (KMTNet), researchers discovered that super-Earth exoplanets are far more common than previously believed. The study found these planets can orbit as far from their stars as Jupiter and Saturn do from our sun.

Andrew Gould, study co-author and Ohio State professor emeritus, explained: “Scientists knew there were more small planets than big planets, but in this study, we were able to show that within this overall pattern, there are excesses and deficits. It’s very interesting.”

While planets close to their stars are easier to detect, those with wider orbits—like super-Earths—are harder to find. Gould estimates that for every three stars, at least one super-Earth exists with a Jupiter-like orbit, suggesting they are widespread.

The team used microlensing, a phenomenon where a star or planet’s gravity bends light from a distant star, creating a temporary brightness increase. By analyzing these light fluctuations, they discovered OGLE-2016-BLG-0007, a super-Earth twice as massive as Earth with an orbit wider than Saturn’s.

The findings split exoplanets into two groups: super-Earths/Neptune-like planets and gas giants like Jupiter/Saturn. This helps scientists understand how planets form and evolve.

The study, led by researchers from China, Korea, Harvard, and the Smithsonian, was published in Science. Comparing their results to planet-formation theories, the team found that while exoplanets can be grouped by mass, their formation processes may differ.

“The dominant theory of gas-giant formation is through runaway gas accretion, but other people have said that it could be both accretion and gravitational instability,” said Gould. “We’re saying we can’t distinguish between those two yet.”

Detecting microlensing events is rare—only 237 of 5,000+ exoplanets have been found this way. Richard Pogge, Ohio State astronomy professor and study co-author, noted: “Finding a microlensing star event is hard. Finding a microlensing star with a planet is hard-squared. We have to look at hundreds of millions of stars to find even a hundred of these things.”

KMTNet’s three telescopes (in South Africa, Chile, and Australia) help scan the cosmos for these events. Ohio State’s Imaging Sciences Lab designed the KMTCam system used in these discoveries.

“We’re like paleontologists reconstructing not only the history of the universe we live in but the processes that govern it,” Pogge said. “Helping to bring both pieces together has been enormously satisfying.”