Exoplanet super-Earths are more prevalent in the universe than earlier research predicted, according to international scientists analyzing recent data from the Korea Microlensing Telescope Network (KMTNet).
Researchers investigated light anomalies created by a recently discovered planet‘s host star. When compared to a larger sample from the KMNet microlensing survey, these anomalies revealed that super-Earths may be located as far from their suns as gas giants in our solar system.
Big Planets in a Big Universe
“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,” said co-author Andrew Gould. “It’s very interesting.”
Astronomers typically find identifying planets orbiting close to their stars easier, while those farther out are much harder to detect. This study suggests that at least one super-Earth with an orbital period similar to Jupiter’s should exist for about one-third of all stars, a finding that implies such planets are very common across the universe.
Microlensing Exoplanets
Gould’s earlier work helped develop the microlensing technique, an observational effect where mass warps space enough to measurably alter light, which was crucial to this new study. When an object passes in front of a distant background object from the observer’s point of view, it creates a “light curve,” making the background object appear brighter.
Astronomers can analyze these variations in brightness to detect exoplanets. Using microlensing signals, Gould’s team discovered the super-Earth OGLE-2016-BLG-0007. This massive exoplanet has an orbit exceeding Saturn’s distance from the Sun and a mass ratio about twice that of Earth. Based on their microlensing work, Gould’s team identified two broad categories of exoplanets: one covering super-Earths and Neptune-like planets, and the other comprising gas giants like Saturn and Jupiter.
Super-Earth Formation
The team’s research offers a new framework for understanding how exoplanets are distributed, providing a stronger baseline for studying planetary formation and evolution. Gould’s team compared their findings with planet formation simulations and found that formation processes can vary significantly even within groups divided by composition and mass.
“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.”
KMTNet and other microlensing instruments could play a key role in answering these outstanding questions.
“Finding a microlensing star event is hard. Finding a microlensing star with a planet is hard-squared,” co-author Richard Pogge said. “We have to look at hundreds of millions of stars to find even a hundred of these things.”
International Cooperation in Astronomy
Despite the power of microlensing, the rarity of ideal alignments has produced just 237 identifications among the more than 5,000 known exoplanets discovered by all methods. However, KMTNet’s system of three high-power telescopes — rotating between South Africa, Chile, and Australia — provides wide coverage that is helping drive new discoveries. The cameras used by KMTNet were designed by the Ohio State University Imaging Sciences Laboratory, underscoring the international nature of this research.
“We’re like paleontologists reconstructing not only the history of the universe we live in but the processes that govern it,” he said. “So helping to bring both of those pieces together into one picture has been enormously satisfying.”
The paper, “Microlensing Events Indicate that Super-Earth Exoplanets are Common in Jupiter-like Orbits,” appeared on April 24, 2025, in Science.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.