In the exciting new film “Project Hail Mary“, humanity sends a ship to the Tau Ceti star system. This mission is a desperate attempt to save Earth from an alien threat, and the key lies in a microbe found on a planet orbiting Tau Ceti.
But how probable is it that Tau Ceti has alien life? And among the thousands of discovered exoplanets, how do scientists decide where to look for life?
A recent study in the Monthly Notices of the Royal Astronomical Society tackles these questions. The researchers focused on 45 exoplanets thought to be the best candidates for hosting life, highlighting methods astronomers can use to find more.
Most exoplanets are discovered through the “transit method.” This involves observing how a star dims when a planet crosses in front of it. A larger planet causes more dimming. Another way is through the star’s “wobble,” caused by the planet’s gravitational pull. As Lisa Kaltenegger, an astrophysicist, explains, the closer the planet is to a star, the more pronounced the wobble appears.
While scientists have found over 6,000 exoplanets, many may not support life. Most of these planets are “hot Jupiters,” giant, gaseous worlds too close to their stars for life as we know it. Some experts suggest that these findings may not mean hot Jupiters are common but rather easier to detect. Kaltenegger’s study suggests that smaller, cooler stars might hold better prospects for finding rocky, habitable planets.
To be a candidate for life, a planet must have a rocky surface and lie within a “habitable zone,” where liquid water can exist. However, scientists recently learned that Tau Ceti might not have planets in its habitable zone, humorously reassuring humanity that the fictional “sun-munching astrophage” couldn’t have come from there.
If we were to search for life, where should we go? Kaltenegger’s team points to several promising candidates. The TRAPPIST-1 system, which has seven rocky planets in its habitable zone, is attracting interest from researchers and is currently being studied by the James Webb Space Telescope.
Another intriguing option is a red dwarf star named TOI-715, which has a super-Earth—three times the mass of Earth—in its habitable zone. But it’s 139 light-years away, a considerable distance for any future missions.
Proxima Centauri, on the other hand, is much closer, just 4.25 light-years away. It hosts an Earth-like planet in its habitable zone, making it a prime candidate for exploration.
Kaltenegger and her team also identified 24 additional planets that lie just outside conventional habitable zones. They refer to these as “planets on the edge.” While these planets may not have liquid water, they could still host life, much like Rocky’s planet in “Project Hail Mary,” where life adapts in unexpected ways.
For Kaltenegger, the quest for life beyond Earth requires creativity and open-mindedness. Focusing too narrowly could cause us to overlook astonishing discoveries. Echoing themes from the movie, she emphasizes that “creativity and imagination are essential in science.” It’s about exploring possibilities and being open to the extraordinary.
