GJ 3323 b is a prominent rocky planet on Lisa Kaltenegger’s list, located approximately 17.5 light-years away in the constellation Eridanus. It orbits a small, cool red dwarf star.

Key Physical Characteristics

• Planet Type: Terrestrial (rocky) Super-Earth.
• Mass: It is about 2.02 times the mass of Earth.
• Orbit: It has a very short “year,” completing an orbit around its star in only 5.1 Earth days.
• The Star: GJ 3323 is an M-dwarf star. Because it is much cooler than our Sun, its habitable zone is located extremely close to the stellar surface.

Habitability & Environment

In Kaltenegger’s 2026 study, GJ 3323 b is highlighted for its position at the inner edge of the habitable zone:

• Incident Light: It receives about 1.2 times the starlight that Earth gets. This makes it a “warm” Earth, potentially similar to the climate of a young Venus or a very hot Earth.
• Surface Gravity: As a Super-Earth, you would feel roughly 1.3 to 1.5 times heavier standing on its surface.
• Tidal Locking: Due to its extreme proximity to the star (orbiting in just 5 days), the planet is almost certainly tidally locked, with one side in perpetual daylight and the other in eternal night.

Scientific Significance

• Atmospheric Characterization: GJ 3323 b is a prime target for the James Webb Space Telescope (JWST) because its short orbital period allows for frequent observations of the planet passing in front of its star (transits).
• Sibling Planet: The system also contains GJ 3323 c, which orbits much further out (every 40 days) and is likely a very cold, frozen world. Comparing these two helps scientists understand how heat affects atmospheric loss.
• Stability: The star GJ 3323 is relatively quiet compared to Proxima Centauri, meaning the planet may have been able to hold onto its atmosphere despite being so close to the star.

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Published @ March 24, 2026 9:15 am