The search for extraterrestrial life is undoubtedly one of the most profound scientific endeavors of our time. If extraterrestrial biological life is found near another world near another star, we will finally learn that life outside our solar system is possible. Finding traces of extraterrestrial biology in distant worlds is extremely difficult. But astronomers are developing new techniques that will be used by next-generation powerful telescopes to accurately measure matter in exoplanet atmospheres. The hope, of course, is to find evidence of extraterrestrial life.
The search for exoplanets has received a lot of attention recently, thanks in part to the discovery of seven small alien worlds orbiting a tiny star, the red dwarf TRAPPIST-1. Three of these exoplanets orbit in the star's potentially habitable zone. That is, in an area near any star in which it will not be too hot and not too cold for water to exist in liquid form.
Everywhere on Earth, where there is liquid water, there is life, so if at least one of the potentially inhabited worlds of TRAPPIST-1 possesses water, there may be life on it.
But the life potential of TRAPPIST-1 remains pure speculation. Despite the fact that this amazing star system is located in the backyard of our galaxy, we have no idea if water exists in the atmosphere of any of these worlds. We don't even know if they have an atmosphere. All we know is how long exoplanets have been in orbit and what their physical dimensions are.
“The first discovery of biosignatures in other worlds may be one of the most significant scientific discoveries of our lives,” says Garrett Rouen, an astronomer at California Institute of Technology. "This will be a major step towards answering one of the biggest questions of humanity: are we alone?"
Rouen works at the Caltech Exoplanetary Technology Laboratory, ET Lab, which is developing new strategies for finding exoplanetary biosignatures such as oxygen and methane molecules. Typically, molecules like these react actively with other chemicals, rapidly disintegrating in the planetary atmosphere. Therefore, if astronomers find a spectroscopic "fingerprint" of methane in the exoplanet's atmosphere, this may mean that alien biological processes are responsible for its production.
Unfortunately, we can't just take the world's most powerful telescope and point it at TRAPPIS-1 to see if the atmospheres of these planets contain methane.
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“To detect molecules in exoplanet atmospheres, astronomers need to be able to analyze the planet's light without being completely blinded by the light of a nearby star,” Rouen says.
Fortunately, red dwarf stars (or M-dwarfs) like TRAPPIST-1 are cool and faint, so the problem will be less severe. And since these stars are the most common type of stars in our galaxy, scientists pay very much attention to red dwarfs in their search for discoveries.
Astronomers use an instrument known as a coronagraph to isolate reflected starlight from an exoplanet. As soon as the coronagraph picks up the dim light of the exoplanet, a low-resolution spectrometer analyzes the chemical fingerprints of that world. Unfortunately, this technology is limited to studying only the largest exoplanets orbiting away from their stars.
ET Lab's new techniques use a coronagraph, optical fibers, and a high-resolution spectrometer that work together to highlight the star's glow and capture a detailed chemical imprint of any world in its orbit. This technique is known as high-dispersion coronography (HDC) and has the potential to revolutionize our understanding of the diversity of exoplanetary atmospheres. A work on this topic was published in The Astronomy Journal.
“What makes HDC so powerful is that it can reveal the spectral signature of a planet even when it is buried in the bright light of a star,” says Rouen. "This allows molecules to be detected in the atmospheres of planets that are extremely difficult to visualize."
"The trick is to split the light into multiple signals and create what astronomers call a high-resolution spectrum that helps distinguish the planet's signature from the rest of the starlight."
All you need now is a powerful telescope to connect the system.
In the late 2020s, the Thirty-Meter Telescope will become the world's largest ground-based optical telescope, and when used in conjunction with HDC, astronomers will be able to explore the atmospheres of potentially habitable worlds orbiting red dwarfs.
“Finding oxygen and methane in the atmospheres of terrestrial planets orbiting M-dwarfs like Proxima Centauri b by the Thirty Meter Telescope will be extremely exciting,” says Rouen. "We still have a lot to learn about the potential habitability of these planets, but it may well be that these planets turn out to be similar to Earth."
It is estimated that there are 58 billion red dwarfs in our galaxy, and most of them are known to have planets, so when the Thirty-Meter Telescope goes into operation, astronomers will be able to find much that was previously inaccessible.
In 2016, astronomers discovered an Earth-sized exoplanet orbiting the closest M-dwarf to Earth, Proxima Centauri. Proxima b also orbits within its star's potentially habitable zone, making it a prime target for the search for alien life. Only four light-years away, Proxima b literally teases us with the opportunity to visit it sometime in the future.
ILYA KHEL