Introduction: A concerted push to find Earth-like worlds
Across billions of galaxies and stars, Earth remains the only known cradle of life. Yet astronomers are driven by the hope that Earth-like planets exist elsewhere and could harbor life. In the ongoing search for habitable worlds, researchers are refining tools to detect planets that resemble our own in size and distance from their stars. A pioneering EU-funded initiative is building a telescope that could dramatically improve our ability to spot such worlds around Sun-like stars, as part of a broader effort that includes the upcoming PLATO mission.
Facing the glare: why Earth-like planets are hard to detect
Scientists have catalogued roughly 6,000 exoplanets, but a precise Earth twin—rocky, similar in size to Earth, orbiting a Sun-like star in a comparable zone—has remained elusive. The difficulty is not a lack of effort but the overwhelming brightness of Sun-like stars. These stars churn with plasma and shifting magnetic fields, creating surface activity that appears as dark spots and granulation. The result is a noisy signal that can swamp the faint dimming caused by a planet passing in front of its star.
Dr. Nuno Santos, a leading Portuguese astrophysicist, explains that the star’s “noise” isn’t merely random; it’s structured and dynamic. This makes distinguishing a planetary transit from stellar variation extremely challenging for ground- and space-based instruments alike.
The PoET telescope: targeting stellar noise at its source
To cut through this noise, Santos and his team at the Institute for Astrophysics and Space Sciences in Portugal are developing PoET—the Paranal Solar Espresso Telescope. PoET is a compact 60-centimeter instrument designed to observe the Sun directly and characterize the noise produced by granulation and related processes. The telescope will operate in Chile, alongside the European Southern Observatory’s Very Large Telescope (VLT), as part of the EU-funded FIERCE project through 2027.
PoET’s strategy is to study the Sun as a proxy for Sun-like stars. By tracing how solar surface phenomena alter light in real time, researchers hope to build a detailed Sun-to-star model of how stellar activity shapes spectra. The approach will be augmented by ESPRESSO—the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations—mounted in Chile. ESPRESSO excels at breaking starlight into its component colors to detect the tiny wobbles or spectral fingerprints that indicate orbiting planets around distant suns.
Connecting solar observations to distant planets
The plan is to link PoET’s solar data with ESPRESSO’s high-precision spectroscopy. By comparing how the Sun’s surface changes correspond to observed spectra, scientists aim to understand how similar processes impact Sun-like stars elsewhere. The ultimate goal is to deliver a cleaner, more accurate stellar spectrum that can be used to sift exoplanet signals from stellar noise when PLATO begins its survey.
PLATO and the future of habitable worlds
PLATO (Planetary Transits and Oscillations of stars), scheduled to launch in 2026, will search for planets around a million stars, prioritizing Earth-like worlds in orbits akin to Earth’s. It will measure planetary radii and, in combination with other measurements, help determine composition and potential habitability. The data from PoET are expected to be essential for PLATO, enabling the mission to distinguish true planet transits from stellar activity with greater confidence.
If PoET succeeds, scientists anticipate results by mid-2026—providing critical insights just as PLATO comes online. The research could influence the interpretation of PLATO’s data and lay groundwork for future missions, including Habitable Worlds Observatory and next-generation European telescopes, which may directly image promising targets and search for biosignatures.
Why this matters: expanding the search for life in the galaxy
Reducing stellar noise is not merely a technical milestone; it expands the catalog of potentially habitable worlds and sharpens our understanding of how common Earth-like planets may be. As Santos notes, the quest to find Earth-like planets around other suns remains one of the big questions in astronomy. With PoET, Europe reinforces a leading role in the global hunt for habitable worlds, ensuring that space-based surveys like PLATO can extract maximum value from their observations.
Looking ahead, the collaboration among PoET, ESPRESSO, and PLATO represents a blueprint for how ground-based and space-based facilities can work in concert to push the frontiers of exoplanet science. The joint effort aims to clarify not only how many Earth-like planets exist, but where they are and what makes them capable of supporting life.
Conclusion
As PoET begins daytime solar observations and ESPRESSO continues its night-time spectroscopic work, the EU’s FIERCE project is carving a path to a more precise, noise-aware view of the cosmos. If successful, PoET will help unlock the next era of exoplanet discovery, enabling PLATO to deliver the first robust census of Earth-like worlds around Sun-like stars and bringing us closer to answering humanity’s enduring question: are we alone?
