The James Webb Space Telescope (JWST), launched last December, has slowly powered its instruments and deployed its solar shield, and is now in the process of aligning its mirrors in preparation for operation.
In a matter of months, the most powerful space telescope ever built will point to the stars. Astronomers hope that what JWST will see will change the way we understand our Universe, just as the Hubble Space Telescope did decades earlier.
One tantalizing ability that JWST offers, which Hubble could not, is the opportunity to directly photograph planets orbiting distant stars and perhaps, just perhaps, detect signs of life.
The ability to remotely detect bio-signatures has been a hot topic in recent years. In our solar system, the recent discovery of phosphine in the atmosphere of Venus sparked speculation that the chemical could be created from a microbial life form.
Similarly, remote sensing experts have proposed that plant life, which uses photosynthesis for energy, could be detected in infrared wavelengths, as chlorophyll absorbs visible light, but looks very bright in the infrared. infrared and would give the overgrown planets a distinct “red border”.
A single-pixel photo of a distant planet might contain enough information to tell us whether biological life is there, based on information stored in the wavelengths of light reaching the telescope lens.
But what about intelligent life? Could JWST detect civilizations similar to ours? How would we look for them? The best answers come from understanding what humanity’s presence on Earth looks like from space.
We emit waste heat (from industry and homes and so on) and artificial light at night, but perhaps more significantly, we produce chemicals that fill our atmosphere with compounds that would otherwise not be present.
These man-made atmospheric constituents could be the thing that could indicate to a distant alien species scanning the galaxy with their powerful telescope that there is intelligent life on earth.
A recent article, available in prepress on arXiv, examined the possibility of using JWST to search for industrial pollutants in the atmospheres of exoplanets. The paper focused in particular on chlorofluorocarbons (CFCs) which, on Earth, are industrially produced as refrigerants and cleaners.
CFCs created a huge hole in the Earth’s ozone layer in 1980, before an international ban on their use in 1987 helped reduce the level of CFCs to less harmful levels.
These “powerful greenhouse agents with long atmospheric residence times”, if found elsewhere in the galaxy, are almost certainly the result of a civilization capable of rampant industrialization.
In other words, some of humanity’s worst by-products, our pollution, may be the very things that make us detectable. And it means we may be able to find other species that can treat their planet’s atmosphere with the same contempt.
There are some limitations to JWST’s CFC search capabilities. If a planet’s star is too bright, it will drown the signal. The telescope will therefore be most successful in observing M-class stars, which are faint and long-lived red dwarfs.
A close example is TRAPPIST-1, a red dwarf 40 light-years away, with several Earth-sized planets orbiting within its habitable zone. JWST would be able to see CFCs on TRAPPIST-1’s planets, because the dim star will not drown the CFC signature in the same way that a bright star like our Sun (a G-type star) would.
Unfortunately, M-class stars are usually not conducive to life, because when young, they are unstable, sending out powerful solar flares that could simply wipe out any nascent life on nearby planets. However, they tend to calm down with age, so it’s not impossible. It just means we should temper our expectations a little.
Whatever we will find, or will not find out there, the fact that we are going to have the ability to look at everything is a game changer.
As the paper concludes, “with the launch of JWST, humanity could be very close to an important milestone in SETI (the search for extraterrestrial intelligence): one in which we are able to detect not only transmissions from nearby stars. powerful, deliberate, transient and highly directional like ours (like the Message of Arecibo), but coherent and passive techno-signatures of the same strength as ours ”.
