In 2025, the first signs of life outside our solar system may be detected.
Crucial to this potential breakthrough is the 6.5-meter diameter James Webb Space Telescope (JWST). Launched in 2021 aboard an Ariane 5 rocket from the coastal city of Kourou in French Guiana, JWST is the largest space telescope ever built. Since it began collecting data, the telescope has enabled astronomers to observe some of the darkest objects in the universe, including ancient galaxies and black holes.
Perhaps more importantly, in 2022, the telescope provided the first glimpse of a rocky exoplanet within a region astronomers call the habitable zone. This is the region around a star where the temperature is just right for liquid water, one of the key ingredients of life as we know it, to exist on the planet’s rocky surface. These Earth-sized planets were discovered 40 light-years away orbiting a small red star called TRAPPIST-1, which has one-tenth the mass of the Sun. The red star is cooler and smaller than the yellow sun, making it easier to detect Earth-sized planets orbiting around it. Nevertheless, signals detected from exoplanets are usually weaker than those emitted by brighter host stars. Discovering these planets was an extremely difficult technological accomplishment.
The next step, detecting molecules in planetary atmospheres, will be an even more difficult astronomical feat. Each time a planet passes between us and its star, that is, each time it passes, the starlight is filtered by the planet’s atmosphere and hits molecules in its path, creating spectral absorption signatures that we can explore. I will create it. These characteristics are very difficult to identify. To accomplish that, JWST will collect enough data from several planetary passes to suppress the signal from its host star and amplify molecular signatures in the rocky exoplanets’ incredibly thin atmospheres. We need to collect data (if we scaled these planets down to the size of a meter (for example, in the case of an apple, at that scale the atmosphere would be thinner than the skin of a fruit). But with a space telescope as powerful as JWST, 2025 could be the year we finally detect these molecular signatures.
But detecting water on TRAPPIST-1’s exoplanets isn’t the only chance to find life on distant exoplanets. For example, in 2024, JWST also revealed potential signatures of carbon dioxide and methane in the atmosphere of planet K2-18b, 124 light-years from Earth. But K2-18b is not a rocky, Earth-like planet orbiting a star in its habitable zone. Rather, it’s more likely to be a giant ball of gas with an ocean of water similar to Neptune (albeit smaller in size). This means that if there is life on K2-18b, it may be in a completely different form than life on Earth as we know it.
In 2025, JWST will likely shed further light on these intriguing detections and confirm for the first time whether life exists on an alien planet many light-years from our world.
