Teegarden’s Star c is one of the most exciting entries on Lisa Kaltenegger’s list because it has one of the highest Earth Similarity Indices (ESI) ever recorded. It is located just 12.5 light-years away in the constellation Aries.

Key Physical Characteristics

• Planet Type: Terrestrial (rocky) world.
• Mass: It is nearly identical in mass to Earth, at approximately 1.11 times Earth’s mass.
• Orbit: It orbits its star very quickly, completing a “year” in only 11.4 Earth days.
• The Star: Teegarden’s Star is an ultra-cool Red Dwarf. It is much smaller and cooler than our Sun, which is why the planet must be so close to stay warm.

Habitability & Environment

In Kaltenegger’s 2026 study, Teegarden’s Star c is highlighted for its “temperate” potential:

• Temperature: Its equilibrium temperature is estimated at -47 °C (-52 °F). However, if it has an atmosphere similar to Earth’s, it could easily maintain liquid water, especially on the side facing its sun.
• Atmosphere: Because the star is very old (at least 8 billion years) and very quiet, scientists believe the planet has had a long, stable time for an atmosphere to develop and for life to potentially evolve.
• Tidal Locking: Like its neighbor (Teegarden’s Star b), it is likely tidally locked. This means it might have a “twilight zone” between the day and night sides where the temperature is most stable.

Scientific Significance

• The “Sibling” System: Teegarden’s Star c has a brother, Teegarden’s Star b, which is even closer to the star and warmer. Together, they provide a perfect laboratory for Kaltenegger and other scientists to study how different distances affect a planet’s ability to hold onto an atmosphere.
• High Priority for JWST: Due to its proximity and the “quiet” nature of its star, it is a top-priority target for the James Webb Space Telescope to look for water vapor and carbon dioxide.

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Published @ March 24, 2026 9:10 am