Since the 1990s, when astronomers began discovering planets beyond our solar system, the field of exoplanet research has expanded dramatically, revealing more than 6,300 confirmed exoplanets and thousands of additional candidates. These discoveries have transformed understanding of planetary systems and fueled the ongoing search for Earthlike worlds that might harbor life.
Many exoplanets are detected indirectly, by observing dips in starlight as planets transit their host stars or through gravitational effects on stellar motion. Direct imaging remains rare and limited to a handful of blurred captures due to the vast distances involved. However, advances such as those provided by the James Webb Space Telescope (JWST) enable scientists to analyze the atmospheres and compositions of these distant worlds, providing insight into their potential habitability.
One of the most Earthlike candidates identified is KOI-456.04, spotted in 2020 by astrophysicist René Heller and colleagues through reanalysis of NASA’s Kepler Space Telescope data. This probable planet, orbiting a sunlike star, is estimated to have a radius 1.9 times that of Earth and receives similar amounts of heat and light, suggesting conditions that could support liquid water and possibly plate tectonics. If confirmed, it would rank among the most promising sites in the quest for extraterrestrial life.
Among confirmed exoplanets, the seven rocky worlds orbiting Trappist-1, a red dwarf star about 40 light-years away, have attracted significant attention. Several of these planets lie within the star’s habitable zone, where temperatures may allow liquid water to exist. Researchers are particularly focused on whether these planets possess atmospheres, which could regulate temperature, protect against radiation, and support biological processes. Early JWST observations indicate that the two innermost planets, Trappist-1b and 1c, likely lack substantial atmospheres, but interest remains high in Trappist-1e, which is Earth-sized and orbits farther out. NASA’s Virtual Planetary Laboratory team, led by Victoria Meadows, is investigating its potential to retain biosignature gases—a possible indicator of life.
Other exoplanet systems offer different perspectives. The Kepler-444 system, studied by astronomer Paul Robertson, contains five Earth-sized planets orbiting an ancient star estimated at 11 billion years old, nearly double the age of the sun. Their proximity to the star likely results in extreme heat, yet their age raises intriguing questions about the longevity and evolution of potentially habitable conditions over cosmic timescales.
The discovery of WD 1856 b has also expanded notions of habitability. This Jupiter-sized gas giant orbits a white dwarf star—the remnants of a star that has exhausted its fuel. Despite the dramatic changes to its host star, the planet survived, suggesting that moons orbiting such gas giants, if present, could be candidates for life, particularly if they possess subsurface oceans.
Astronomers emphasize that studying a diverse array of exoplanets helps illuminate fundamental aspects of planetary formation and conditions for life, including those that may be strikingly different from Earth. Looking ahead, missions like NASA’s planned Habitable Worlds Observatory for the 2040s aim to detect Earthlike planets around nearby stars and analyze their atmospheres for signs of biological activity.
Researchers remain optimistic about the prospects of discovering life beyond Earth. As planetary scientist Sara Seager notes, there is no single “favorite” planet because each new discovery expands the possibilities and refines strategies for identifying worlds that might host life.