GJ 273 b, also widely known as Luyten’s Planet, is one of the most famous and well-studied “Super-Earths” due to its proximity to our solar system—just 12.4 light-years away.

Key Physical Characteristics

• Planet Type: Terrestrial (rocky) Super-Earth.
• Mass: It is about 2.89 times as massive as Earth.
• Orbit: It orbits its red dwarf star, Luyten’s Star (GJ 273), every 18.6 Earth days.
• Location: It sits right in the middle of the Habitable Zone, making it a prime candidate for liquid water.

Habitability & Environment

In Lisa Kaltenegger’s models, Luyten’s Planet is particularly interesting because it receives a level of starlight very similar to Earth’s:

• Incident Light: It receives about 1.06 times the solar energy that Earth gets from the Sun. This makes its potential climate very “Earth-like” if it has a similar atmosphere.
• Temperature: If it has an atmosphere like ours, the average surface temperature could be around 19 °C (66 °F), which is very comfortable for life as we know it.
• Tidal Locking: Like most planets around red dwarfs, it is likely tidally locked, meaning it has a permanent “day side” and “night side.”

Why it’s Famous: The “Message to GJ 273 b”

This planet gained massive public attention in 2017 because of a project called “Sónar+D.”

• Active SETI: Scientists beamed a radio message containing 33 short musical pieces and mathematical tutorials toward the planet.
• The Wait: Since it is 12.4 light-years away, if there is an intelligent civilization there that receives the message and decides to reply immediately, we could receive an answer as early as 2042.

Scientific Priority

Because the host star is relatively quiet (not prone to many violent flares), GJ 273 b is a top-tier target for atmospheric characterization. Astronomers are looking for:

• Water Vapor: To confirm the presence of oceans.
• Oxygen and Methane: To search for signs of biological activity.

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Published @ March 24, 2026 9:08 am