James Webb Space Telescope (JWST) would be able to detect life on Earth if it were observing us from another star system in the Milky Way. This discovery only confirms the capabilities of the instrument launched a few years ago. It also holds promise that JWST could detect alien civilizations while observing distant worlds in our galaxy.

Since its launch, the space telescope has primarily been peering into the deepest corners of the cosmos. Its primary goal is the search for clues about the early universe. But one of its secondary objectives is to analyze the atmospheres of nearby exoplanets, planets beyond the Solar System, in order to search for traces of biological life, known as biosignatures and chemical substances.

A Confirmation for JWST

Despite being the most advanced telescope currently in operation, it is still unclear how well JWST will be able to detect signs indicative of life. To answer this question, researchers have decided to conduct some tests. If James Webb were, hypothetically, placed anywhere in the galaxy, would it be able to detect life on Earth?

In the new study, posted on arXiv on August 28th (ref.), researchers used a spectrum of Earth’s atmosphere as a reference. They reduced the data quality to mimic how it would appear to a distant observer and used a computer model that replicates JWST’s analysis capabilities. The goal is to understand if the telescope can detect the major biosignatures and technosignatures from the dataset under examination, including methane and oxygen, produced by life, as well as nitrogen dioxide and chlorofluorocarbons (CFCs), produced by humans.

Results show that James Webb can detect all major indicators of intelligent and non-intelligent life in Earth’s atmosphere. Alteration of the data used is roughly comparable to JWST’s observations of the planets in the TRAPPIST-1 system. The star system contains seven exoplanets orbiting around a red dwarf star about 40 light-years from Earth.

How Far Can Its Gaze Reach

This suggests that James Webb would be capable of detecting life or alien civilizations on exoplanets within 40/50 light-years from Earth. Only about 20 exoplanets have been officially discovered within a 50-light-year radius from us. But based on the number of stars in this region of space, experts predict there could be up to 4,000 exoplanets within JWST’s reach.

Despite these encouraging analyses, no one can guarantee 100% that JWST will be able to detect life on other planets. Detecting biosignatures and technosignatures on other worlds “may prove difficult to interpret without a contextual understanding of the habitable environment”, wrote the researchers. In this analysis, the team already knew which molecules to look for. On an exoplanet with different conditions and potential forms of life or alternative technologies, such signs of life may not be as evident.

On the other hand, James Webb has already made interesting discoveries about exoplanets near Earth. The telescope detected water on the exoplanet GJ1214b, Neptune-sized, and found that TRAPPIST-1b, the second-closest exoplanet to the star, has no atmosphere. The spacecraft has also glimpsed a massive dust storm in the atmosphere of VHS1256b, a super-Jupiter exoplanet 40 light-years away. But much farther in the cosmos, James Webb has also spotted carbon compounds in a newly born star system more than 1,000 light-years from us.

Stefano Gallotta
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