Produced by: Tarun Mishra
Since the first confirmed exoplanet orbiting a sunlike star was discovered in 1995, scientists have identified over 5,000 distant worlds, with many of these findings made by NASA's Kepler space telescope.
Launched in 2009, the Kepler space telescope played a crucial role in exoplanet discovery, finding more than 2,600 exoplanets before its retirement in 2018. The mission aimed to determine the prevalence of Earth-like planets in the Milky Way.
Astronomers have long sought to find a true "alien Earth," and recent discoveries have shown that small, rocky planets like Earth are common in our galaxy, raising hopes for finding a planet with conditions suitable for life.
For an exoplanet to be considered potentially life-friendly, it must be relatively small, rocky, and located in the habitable zone of its star—a region where liquid water can exist. Other factors like atmospheric composition and the star's activity level are also important.
Gliese 667Cc, located 22 light-years away, is at least 4.5 times the mass of Earth and lies in the habitable zone of its red dwarf star. However, its proximity to the star may expose it to harmful flares.
Discovered 600 light-years away, Kepler-22b was the first planet found by Kepler in the habitable zone of its star. This "super-Earth" is about 2.4 times the size of Earth, but its composition—rocky, liquid, or gaseous—remains unclear.
Kepler-69c, located 2,700 light-years away, is about 70% larger than Earth and orbits its star in 242 days. Despite its size and orbit, its star's lower luminosity places it in the habitable zone, though its composition is still unknown.
Kepler-62f, situated 1,200 light-years away, is about 40% larger than Earth and orbits a cooler star within the habitable zone. Due to its size, it is considered potentially rocky with the possibility of holding oceans.
Kepler-186f, about 500 light-years from Earth, is only 10% larger than Earth and lies on the outer edge of its star's habitable zone. The planet's parent star is a red dwarf, making it less of an Earth twin, but still a significant find.
Kepler-442b, discovered 1,194 light-years away, is 33% larger than Earth and completes an orbit every 112 days. Studies suggest it receives enough light to support photosynthesis, making it a strong candidate for hosting life.
The TRAPPIST-1 system, located 40 light-years away, contains seven Earth-sized planets. TRAPPIST-1e is considered the most likely to support life, with some planets in the system possibly holding more water than Earth's oceans.