Potentially Habitable Exoplanets: The Search for Earth 2.0

The quest to identify terrestrial worlds capable of sustaining human life involves evaluating several critical factors: the planet's mass and radius, its distance from the host star (the circumstellar habitable zone), and the presence of a stable atmosphere.[1] [2] While current technology cannot yet definitively confirm "breathable" oxygen-rich atmospheres or the exact volume of liquid surface water, astronomers use the Earth Similarity Index (ESI) to rank candidates based on their physical properties relative to Earth.[3] [4]

The following list identifies ten of the closest and most promising potentially habitable exoplanets, prioritized by their proximity to Earth and their likelihood of possessing rocky compositions and temperate climates.

1. Proxima Centauri b

Located just 4.24 light-years away, Proxima Centauri b is the closest known exoplanet to our solar system.[5] It orbits within the habitable zone of a red dwarf, Proxima Centauri. It has a minimum mass of approximately $1.27M_{\oplus }$ (Earth masses).[2] [6] While its proximity makes it a primary target for future interstellar probes, it faces challenges: it is likely tidally locked, meaning one side faces the star perpetually, and it is exposed to intense ultraviolet and X-ray radiation that could strip away a nascent atmosphere.[7] [8]

2. Wolf 1061c

At a distance of roughly 14 light-years, Wolf 1061c is a "super-Earth" orbiting a quiet red dwarf star.[9] It has an ESI of 0.81 and resides in the optimistic habitable zone.[1] [10] Its mass is estimated at $4.3M_{\oplus }$, which suggests a rocky composition, though its higher gravity would be significant for human visitors. Its atmosphere's stability is a subject of ongoing study.[1]

3. Teegarden’s Star b

Teegarden b is one of the most Earth-like planets discovered to date, with an ESI of 0.90 to 0.97.[3] [4] Located 12.5 light-years away, it orbits a very old, stable red dwarf. Because the host star is "quiet" (lacking frequent flares), Teegarden b has a higher probability of retaining a thick atmosphere and liquid water.[4] [11] Its surface temperature is estimated to be a temperate ${28}^{\circ }\mathrm{\text{C}}$ (${82}^{\circ }\mathrm{\text{F}}$), assuming an Earth-like greenhouse effect.[3]

4. Gliese 1002 b

Discovered in 2022, Gliese 1002 b is located 16 light-years away.[1] It is an Earth-mass planet ($1.08M_{\oplus }$) orbiting in the habitable zone of its host star.[12] Because the star is a quiet M-dwarf, the planet is considered an excellent candidate for atmospheric characterization by future telescopes to search for water vapor and oxygen.[1] [12]

5. Ross 128 b

Ross 128 b is located 11 light-years away and is often cited as a more "life-friendly" alternative to Proxima b.[2] [6] Its host star is an inactive red dwarf, meaning the planet is not subjected to the devastating flares common in other systems.[5] It has a mass of $1.4M_{\oplus }$ and receives about 38% more starlight than Earth, placing its equilibrium temperature in a range that could support liquid water.[7] [13]

6. Luyten b (GJ 273 b)

Orbiting Luyten's Star at a distance of 12.2 light-years, this planet is a super-Earth with a mass approximately $2.89$ times that of Earth.[3] It sits squarely in the habitable zone and has an ESI of 0.86.[1] [3] Scientists have already sent a radio message toward this system (Sónar Calling GJ 273b) in hopes of contacting potential civilizations, highlighting its status as a top-tier candidate.[10]

7. Gliese 667 Cc

Located 23.6 light-years away in a triple-star system, Gliese 667 Cc has an ESI of 0.84.[1] [2] It is at least 4.5 times as massive as Earth.[5] Despite orbiting a red dwarf, it receives about 90% of the energy Earth receives from the Sun, but much of it is in the infrared spectrum.[[5]] This could allow for liquid water if the atmosphere provides sufficient insulation.[14]

8. TRAPPIST-1e

Part of the famous seven-planet system 40 light-years away, TRAPPIST-1e is considered the most habitable of the group.[2] [3] It is almost exactly Earth-sized and is likely a rocky world with an iron core.[4] [5] Recent studies suggest it may have a compact atmosphere, unlike its inner siblings which appear to have lost theirs.[1] [6]

9. Gliese 12 b

A relatively recent discovery at 40 light-years, Gliese 12 b is an Earth-sized planet orbiting a cool red dwarf every 12.8 days.[1] It is notable because its equilibrium temperature is estimated at ${42}^{\circ }\mathrm{\text{C}}$ (${107}^{\circ }\mathrm{\text{F}}$), which is significantly cooler than most transiting Earth-sized planets.[1] This makes it a "temperate" world where an atmosphere could potentially support liquid water.[1]

10. LHS 1140 b

Located 41 light-years away, LHS 1140 b is a "Super-Earth" that is denser than Earth, suggesting a rich iron content.[1] [10] Recent observations by the James Webb Space Telescope (JWST) have led scientists to believe it might be an "ocean world" or a "Hycean" planet with a nitrogen-rich atmosphere, making it one of the most promising targets for finding liquid water outside our solar system.[1] [6]