An international research team, including the Korea Astronomy and Space Science Institute (KASSI), discovered a "long-period super-Earth" orbiting at a distance greater than Saturn, using the Exoplanet Exploration System (KMTNet).
The Korea Aerospace Research Agency (Korea Aerospace Agency) announced on the 25th that this research achievement has been published in the international journal "Science." The research team also presented evidence supporting the theory that planets undergo different formation processes based on their size by analyzing exoplanet data observed with KMTNet over several years.
An exoplanet is a planet that orbits a star other than the Taeyang. One type of exoplanet, a super-Earth, is a rocky, Earth-like planet with a mass between about 1 and 10 times that of Earth.
The newly discovered "OGLE-2016-BLG-0007Lb" has a mass 1.3 times that of Earth and is located approximately 14,000 light-years away from Earth (1 light-year is the distance light travels in one year, about 9.46 trillion kilometers). It orbits a host star that has a mass equivalent to 0.6 times that of the Taeyang, located at a distance of 1.5 billion kilometers, about 10 times the distance between the Taeyang and Earth.
This exoplanet has the smallest mass among the long-period super-Earths discovered so far and is the planet that is farthest from its host star. Its orbital period is estimated to be about 40 years.
KASSI discovered this exoplanet using its self-developed KMTNet system. KMTNet utilizes the microgravity lensing method. When observing a star, if an invisible celestial object passes between the star and the observer, the star's brightness increases due to the object's gravitational field. The existence of the exoplanet is confirmed based on subtle changes in brightness. Since KMTNet became operational, a total of 227 exoplanets have been directly discovered.
The research team analyzed 63 exoplanets discovered by KMTNet from 2016 to 2019 to establish a sample of long-period exoplanets. As a result, many super-Earths and gas giant planets were discovered. Among 100 stars, about 35 are super-Earths and about 12 are gas giant planets. This supports the existing prediction that there would be more terrestrial planets than gas giant planets among long-period exoplanets.
This research also provides important clues about the formation process of planets. Astronomers predicted that if terrestrial planets and gas giant planets formed in different ways, then terrestrial planets would be abundant while planets of intermediate size would be rare. This observation supported the prediction that super-Earths and gas giant planets were discovered in abundance, while planets of intermediate size appeared rarely.
Jung Yeon-gil, a senior researcher at KASSI who led the study, noted, "The observation results validate that terrestrial planets and gas giant planets have different formation processes, as predicted by the theory, and confirm that many long-period super-Earths exist in the universe." He added that exoplanets are important clues to understanding the formation and evolution of planets.
The research team plans to use KMTNet to secure more exoplanet samples and continue precise observations and analyses.
References
Science (2025), DOI: https://doi.org/10.1126/science.adn6088