By 2025, we could detect the first signs of life outside our solar system.
Crucial for this possible advance is the James Webb Space Telescope 6.5 meters in diameter (JWST). Launching aboard an Ariane-5 rocket from Kourou, a coastal city in French Guiana, in 2021, the JWST is our largest space telescope to date. Since it began collecting data, this telescope has allowed astronomers to observe some of the faintest objects in the cosmos, such as ancient galaxies and black holes.
Perhaps most importantly, in 2022 the telescope has also provided us with the first glimpses of rocky exoplanets within what astronomers call the habitable zone. This is the area around a star where the temperatures are just right for the existence of liquid water, one of the key ingredients of life as we know it, on the planet’s rocky surface. These Earth-sized planets were found orbiting a small red star called TRAPIST-1a star 40 light-years away with one-tenth the mass of the sun. Red stars are cooler and smaller than our yellow sun, making it easier to spot Earth-sized planets orbiting them. However, the detected signal from exoplanets is usually weaker than that emitted by the much brighter host star. Discovering these planets was an extremely difficult technical achievement.
The next stage, the detection of molecules in the atmospheres of the planets, will be an even more difficult astronomical feat. Every time a planet passes between us and its star, when it transits, starlight filters through the planet’s atmosphere and hits molecules in its path, creating spectral absorption features that we can look for. These characteristics are very difficult to identify. To achieve this, JWST will need to collect enough data from multiple planetary transits to suppress the signal from the host star and amplify the molecular features of the incredibly thin atmospheres of rocky exoplanets (if you shrunk these planets down to the size of an apple , for example, at this scale its atmosphere would be thinner than the skin of the fruit). However, with a space telescope as powerful as the JWST, 2025 could be the year we can finally detect these molecular signatures.
Detecting water on TRAPPIST-1 exoplanets, however, is not our only chance to find life on distant exoplanets. In 2024, for example, the JWST also revealed possible signs of carbon dioxide and methane in the atmosphere of K2-18ba planet located 124 light years from Earth. K2-18b, however, is not a rocky Earth-like planet orbiting its star in the Habitable Zone. Instead, it is more likely a giant ball of gas with a water ocean similar to Neptune (though smaller in size). This means that if there is life on K2-18b, it could have a completely different form than life as we know it on Earth.
In 2025, the JWST will likely shed more light on these tantalizing detections and hopefully confirm, for the first time, whether life exists on alien worlds light years away from our own.
