Source: cnBeta
The James Webb Space Telescope (JWST), launched last December, has been slowly powering up its instruments and unfolding its visors, which are now aimed at its mirrors and ready for use. In a matter of months, the most powerful space telescope ever built will set its sights on the stars. Astronomers hope that what JWST sees will change the way we understand the universe, just as the Hubble Space Telescope did decades ago.
One of the alluring abilities offered by JWST that Hubble can't offer is the opportunity to directly image planets orbiting distant stars, perhaps detecting signs of life. The possibility of remote detection of biometrics has been a hot topic in recent years. In our own solar system, the recent discovery of phosphine in Venus's atmosphere has sparked speculation that the chemical may have been created by microbial life.
Similarly, remote sensing experts have proposed that plant life, which uses photosynthesis to obtain energy, can be detected in the infrared band because chlorophyll absorbs visible light but is brightly displayed in the infrared, which would give planets covered with leaves a distinct "red edge." Depending on the information stored by the wavelengths of light reaching the telescope lens, a single-pixel photograph of a distant planet may contain enough information to tell us if there is biological life there.
A recent paper on ArXiv in preprint investigated the possibility of using JWST to search for industrial pollutants in the atmospheres of exoplanets. The paper focuses in particular on chlorofluorocarbons (CFCs), which are industrially produced on Earth as refrigerants and cleaners. Chlorofluorocarbons created a huge void in Earth's ozone layer in the 1980s. If these potent greenhouse gas preparations with longer atmospheric residence times were to be found elsewhere in the Milky Way, they would almost certainly be the result of an industrialized civilization.
JWST's CFC discovery capabilities have some limitations. If a planet's star is too bright, it will drown out the signal. As a result, the telescope will have the greatest success by looking at M-class stars, which are dim, long-lived red dwarfs. A nearby example is TRAPPIST-1, a red dwarf star 40 light-years away with several Earth-sized planets orbiting its habitable zone. JWST will be able to see CFC on the planet TRAPPIST-1 because dim stars don't drown out CFC signals like bright stars like our Sun (G-type stars).
Unfortunately, M-class stars are generally detrimental to life, because when they are young, they are unstable and emit powerful solar flares that could wipe out any new life on nearby planets. However, as they age, they do tend to calm down, so it's not impossible to spawn civilizations on nearby planets.