Since the dawn of civilization, humanity has wondered whether we are alone in the universe. Some people—myself included—believe that there is surely life beyond Earth, but that they don’t want anything to do with us. However, that doesn’t stop us from searching for other habitable worlds, a kind of twin planet to our own Earth. Today, astronomy has set its sights on a potential planet quite close by. It is located in Proxima Centauri, our closest stellar neighbor, only four light-years away. Thanks to the James Webb Space Telescope, the most sophisticated stellar observation tool ever built, we can monitor this planet quite closely and try to see its climatic conditions.
It is not yet fully confirmed, but computer simulations seem to confirm that “Proxima b” does exist, a rocky planet that could have all the makings of supporting life.
Our neighbor, the Proxima Centauri system
The Proxima Centauri system is part of the Alpha Centauri system. Within it are the stars Alpha A and B (for some reason, astronomers have been too lazy to give them more complicated names). These two stars are very similar in composition, size, and brightness to the sun in our own solar system. However, there is a third star: Proxima Centauri, a red dwarf that is much smaller, cooler, and dimmer.
Its low luminosity, which under normal conditions would be a disadvantage, becomes a key advantage for direct observation of planets. This is because the faint glow of a planet is easier to detect when it is close to a star with such soft light. The planet we already know, Proxima b, orbits in what is considered the habitable zone of its star. The habitable zone is the region where liquid water could (potentially) exist on the surface of a planet.
However, there is one big caveat: red dwarf stars, while dim, are also prone to powerful and frequent eruptions and flares. These bursts of energy could have stripped away the atmospheres of their nearby planets. This is why astronomers are not claiming victory just yet: although the planet appears to have a chemical composition similar to Earth and contain water—essential for the beginning of life as we know it—Proxima Centauri’s solar storms could have stripped it of its protective atmosphere.
The keen eye of James Webb
Although astronomers are neither optimistic nor completely defeatist, they have made sure to point James Webb’s eye toward this star system. They want to study the infrared heat signature emitted by these planets.
The James Webb telescope is the only one designed to operate in infrared wavelengths. In other words, it does not take photographs as humans would, but rather studies the spectrum of heat emitted by different celestial bodies. Thanks to this type of technology, it can see perfectly through cosmic dust and detect heat signatures that would otherwise be completely invisible to us.
A key instrument in this mission is the MIRI (Mid-Infrared Instrument), which is responsible for capturing and analyzing these heat signatures. This technique is called coronography. By blocking the star’s brightness, the coronagraph allows the planet’s radiation to be visible. However, the technical difficulty is immense. The residual glare from Proxima Centauri is so vast that it can easily drown out the planet’s tiny thermal signal.
The results of the simulation
The public simulation by the scientific journal Ícarus was quite meticulous: its purpose was to test the absolute limits of the James Webb telescope’s ability to image an exoplanet. Thanks to this, we have been able to see the clear limits of the telescope’s current range. The James Webb will probably not be able to detect a twin planet of Earth with the same size and temperature as ours. However, it could detect a “super-Earth.”
This super-Earth would be a significantly larger rocky world, 1.5 to two times the radius of Earth. In addition, this planet would have to be relatively warm to emit enough infrared radiation to be picked up by the James Webb telescope. For now, the telescope will continue to search for rocky exoplanets that may contain interstellar neighbors.