The search for life beyond the solar system is moving from simple discovery toward careful target selection. With more than 8,000 confirmed exoplanets, astronomers now face a key question: which worlds deserve priority for observation with the most advanced telescopes?

In a recent SETI Live discussion, SETI Institute astronomer Dr. Franck Marchis spoke with Cornell astronomer Abigail Bohl and Dr. Lisa Kaltenegger, Director of Cornell’s Carl Sagan Institute, about a study that identifies 45 planets as especially promising for habitability research. Instead of looking for an exact “Earth 2.0,” the study focuses on planets that may help scientists understand where habitable conditions can exist.

Using stellar data from the European Space Agency’s Gaia mission, which mapped around 1.7 billion stars, the researchers estimated how much energy each planet receives from its host star. This allowed them to examine the boundaries of the habitable zone: the region where liquid water could exist on a planet’s surface. Planets near the inner edge may experience runaway greenhouse effects like Venus, while those near the outer edge may become globally frozen, similar to Mars. Studying these boundary worlds is important because it helps scientists test climate models and refine our understanding of atmospheric stability. It may also offer insight into Earth’s distant future, as the Sun gradually becomes brighter over billions of years.

Many of the 45 selected planets orbit red dwarfs, or M-dwarfs, which make up roughly 80% of the stars in the Milky Way. These stars are smaller and cooler than the Sun, making planetary signals easier to detect. The TRAPPIST-1 system, with seven Earth-sized planets, remains a particularly valuable example.

The next step is searching planetary atmospheres for biosignatures, such as combinations of gases that are difficult to explain without life. The same target list can also support technosignature searches using instruments like the Allen Telescope Array and LaserSETI. Overall, the study provides a practical roadmap for focusing future observations on the worlds most likely to reveal signs of life.

Visit the site to watch the full SETI Live conversation and read the full article.