The numbers speak clearly: of 5.788 exoplanets confirmed, only 210 are “Earth-like”. And none orbit a star like our Sun. PLATO, ESA's new mission, could change that statistic—or rather, overturn it.
PLATO Launches Habitable Planet Hunting Challenge
What I find fascinating about PLATO is the project’s ambition: to search not just for planets, but for potential new homes for humanity.
The mission, which will launch in 2026, will use 26 cameras to scan the sky, including 24 “normal” cameras divided into 4 groups and 2 “fast” cameras for the brightest stars.
Andreas F. Krenn, PhD student at the Space Research Institute ofAustrian Academy of Sciences, explains the real difficulty of this research. To detect a planet like Earth, we must observe incredibly small variations in stellar brightness: we are talking about 0,0084% of the total light.
It’s like trying to see a Galapagos tortoise move from light-years away: that’s about the precision required to identify the motion of a star caused by an Earth-sized planet.
A revolutionary technology
PLATO's real strength lies in its multidisciplinary approach. It will not limit itself to observing the stars: it will combine high precision photometry, data analysis tools cutting edge, a program dedicated to the study of stellar variability e a follow-up campaign from the ground.
The most innovative feature is the ability to detect the transit of an Earth-like planet with a single observation. Current instruments, such as the telescope CHEOPS of ESA, instead require multiple observations to reach the necessary precision.
PLATO will continuously observe the same area of sky for at least two years, a strategy that will allow it to monitor thousands of stars simultaneously. It is an approach that is unprecedented in the search for exoplanets.
The signs of life
When we search for habitable planets, we know exactly what to look for. Researchers focus on “biosignals”: oxygen, carbon dioxide, methane, ammonia e water vapor in the atmosphere. They also look for the “vegetation red edge” (VRE), an indicator of photosynthesis on the surface.
Until now, it has been extremely difficult to obtain these data from terrestrial planets orbiting stars similar to the Sun. The problem is that these planets tend to orbit closer to their star, making observing their atmospheres a herculean task.
PLATO could change all that. Its unprecedented precision promises to overcome these technical obstacles that have limited our discoveries so far.
PLATO, future prospects
The team led by Krenn conducted simulations (I'll link them here) using data from our Sun as a reference. The results are promising: PLATO should be able to accurately detect the sizes of Earth-like planets, one of its primary goals.
However, as Krenn points out, there is still a lot of work to be done. The simulations have focused only on short-term stellar variability, but in reality PLATO will have to deal with numerous sources of noise that could mask the planetary signals.
The good news is that PLATO will not be alone in this research. It will work in synergy with other next-generation tools such as the James Webb space telescope, the telescope ARIEL and the Nancy Grace Roman Space Telescope. Together, they could finally allow us to say with certainty whether a planet is “habitable” or even “inhabited.”
The Promise of a New Earth
The search for a “sister planet” of Earth is not just a scientific question. It is a quest that touches on some of humanity's deepest questions: Are we alone in the universe? Are there other worlds that could host life?
PLATO represents our most ambitious attempt yet to answer these questions. With its cutting-edge technology and innovative approach, it may be the tool that allows us to finally find our “Earth 2.0.”
And perhaps, in a few years, we will no longer talk about “potentially habitable” planets, but we will finally have scientific certainty of the existence of other worlds where life could thrive.
