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A rocky exoplanet named GJ 3378b was discovered in 2024 orbiting a red dwarf star just 25 light-years from Earth, in the direction of the constellation Camelopardalis. Based on radial velocity data, scientists estimate this planet is approximately 2.3 times Earth’s mass, classifying it as a “Super Earth.” Recent revisions by a team led by researchers from the University of California, Irvine, suggest this planet resides within its star’s habitable zone (HZ).
The research was headed by Paul Robertson, an Associate Professor of Physics and Astronomy at UC Irvine. He collaborated with experts from the University of Texas Center for Planetary Systems Habitability, the Astrophysics & Space Institute, the Anton Pannekoek Institute for Astronomy, the Center for Exoplanets and Habitable Worlds, the Astrobiology Research Center, NASA’s Jet Propulsion Laboratory (JPL), Goddard Space Flight Center, along with various other academic and research institutions.
Red dwarf stars are the most common type of star in the universe, making up 70-75% of stars in the Milky Way and up to 90% in elliptical galaxies. Studies of nearby red dwarfs indicate they frequently form rocky planets within their habitable zones, making them prime targets in the search for extraterrestrial life. However, red dwarfs are known for their variability and flare activity, which could potentially make planets in their habitable zones inhospitable. Their faintness also complicates the detection of Earth-like planets, which are small compared to other types like Super Earths, mini-Neptunes, or gas giants.
To detect these planets, astronomers rely on specialized tools, such as the Habitable-zone Planet Finder (HPF) instrument mounted on the Hobby-Eberly Telescope. This device measures tiny stellar wobbles caused by orbiting planets through radial velocity techniques.
Paul Robertson explained in a McDonald Observatory release: “Our approach is ‘follow the water.’ It’s the one resource all known life needs, so that’s what we target when looking for environments capable of supporting life. The Habitable-zone Planet Finder is tailored for infrared light because, as stars get cooler and smaller, most of their energy emissions are in infrared wavelengths. By using an infrared spectrometer on a large telescope, we gain increased ability to observe faint stars.”
Since 2018, the HPF has helped astronomers identify numerous exoplanets and assess which might be potentially habitable. Michael Endl, an astronomer at the University of Texas and the McDonald Observatory, emphasized: “Precision is everything. Detecting low-mass planets requires spotting very subtle signals. If your instruments aren’t precise enough, you simply won’t find them.”
Initially, GJ 3378b was thought to be five times more massive than Earth. A planet this massive could retain an atmosphere, but its density might be so high as to make surface life impossible. The latest analysis reduces its estimated mass to about 2.3 times Earth’s, increasing the chances it might lack a thick, crushing atmosphere. Additionally, the refined orbital period from 25 days to 21 brings the planet firmly into the star’s habitability zone.
However, being closer to its star could mean higher radiation levels, which might strip away any atmosphere over time. More detailed observations will become feasible as upcoming telescopes come online, including the Giant Magellan Telescope (GMT), the Extremely Large Telescope (ELT), and the Habitable Worlds Observatory (HWO). These advanced telescopes will be equipped with enormous mirrors, adaptive optics, coronagraphs, and spectrometers, enabling direct imaging and search for signs of life, called biosignatures. Endl noted, “Our ultimate goal is biosignatures. We want to find out if we’re truly alone in the universe. Currently, we’re in the reconnaissance phase, studying nearby stars because they are the easiest to analyze for signs of life.”
GJ 3378b is a significant step toward understanding our planetary neighbors and identifying which worlds might support life beyond Earth.
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