Sub-Earth-sized planet candidate observed around the red dwarf Gliese 774 A

Data from the TESS space telescope reveals a sub-Earth-sized planet candidate orbiting within the Gliese 774 binary star system. Located 12.86 parsecs away, the signal likely originates from the primary star, Gliese 774 A. If confirmed, this world would be one of the smallest planets identified in a nearby system, offering a valuable opportunity for future studies of terrestrial planet atmospheres.

Star system: L 115-21 | Distance from the Sun: 41.9 light years

A small planet candidate has been identified in the binary star system known as Gliese 774. The object, which is smaller than the Earth, orbits its host star approximately every 4.2 days. Observations from the Transiting Exoplanet Survey Satellite (TESS) captured the planet as it passed in front of its star, briefly blocking a tiny fraction of the starlight. This periodic dimming event allowed for the identification of the candidate despite the complex environment of a binary system, where two stars orbit one another in close proximity.

To confirm the signal, analysts examined light data collected over eight separate TESS sectors between 2019 and 2026. By applying advanced statistical tests, they ruled out common false positives such as distant eclipsing binary stars or background objects. While most evidence points to the primary star, Gliese 774 A, as the host, some data from 2026 showed slight irregularities in the location of the signal. Further high-resolution ground-based observations are necessary to confirm if the planet truly circles Gliese 774 A or if the signal arises from the companion star, Gliese 774 B.

If the planet orbits the primary star as expected, its physical properties suggest a very warm, rocky world. With a radius approximately 70 percent that of Earth, it receives roughly 15 times more stellar radiation than our planet. This results in an equilibrium temperature of approximately 548 Kelvin, or 275 degrees Celsius. Because it is not yet officially validated, the scientific community continues to review the data to ensure the signal is not a measurement error caused by the proximity of the two stars.

Key findings
The planet candidate has a radius of 0.70 Earth radii.
It orbits its host star every 4.225138 days.
The planet experiences a high level of stellar radiation, roughly 15 times that of Earth.
The equilibrium temperature of the planet is estimated at 548 Kelvin.
The signal is primarily attributed to the star Gliese 774 A, though host verification is ongoing.

Scientific study

A sub-Earth-sized TESS planet candidate in the nearby M-dwarf binary GJ 774, most likely orbiting GJ 774 A (TIC 351339274) (external link)