A new study published in the Monthly Notices of the Royal Astronomical Society screened more than 6,000 currently known exoplanets and finally identified 45 "Earth-like worlds" that are the most promising to harbor life. They are all located in the habitable zone of their respective stars and can theoretically contain liquid water.
The research team also listed an additional 24 candidate planets under the more conservative "three-dimensional habitable zone" model to explore whether planets are still likely to remain habitable under extreme high temperature or extreme low temperature boundary conditions.
These targets are vividly likened to the destinations of the real-life spaceship "Project Hail Mary": if humans really want to expedition to outer galaxies to save the earth, these planets are currently the first choice list worthy of "betting". The selected planets include well-known "potentially habitable" planets such as Proxima Centauri b, TRAPPIST-1 d/e/f/g, and Kepler-186f, as well as emerging targets such as TOI-715 b that were not previously popular but are relatively close to the Earth in terms of radiation flux, planet size, and orbital position.
The research team used "Earth-like" as the core of the screening: priority was given to rocky planets, the orbit around the star should fall in the "Goldilocks zone" (not too hot, not too cold), and comprehensive consideration was given to star type, radiation intensity, and whether the planet is suitable for atmospheric observations using methods such as transit or radial velocity. Among them, TRAPPIST-1 d/e/f/g and LHS 1140 b, which is about 48 light-years away from the Earth, are regarded by the author as the most worthy of investment. If they can maintain a thick enough atmosphere, there is hope that liquid water can exist on the surface for a long time.
The study also provides a "road map" for follow-up observations, pointing out that the James Webb Space Telescope, the Nancy Grace Roman Space Telescope scheduled to be launched in 2027, and the European Extremely Large Telescope (ELT) will be key tools for detecting the atmospheres of these planets and searching for chemical signs of life in the next dozen years. The researchers emphasized that this list does not mean that "life already exists" on these planets. Instead, it sets out a "target list" with the highest priority for the search for extraterrestrial life given humanity's limited observation resources, greatly narrowing the scope of screening one by one from more than 6,000 exoplanets.