Cutting through the noise in the search for Earth-like worlds
Across billions of galaxies and countless stars, Earth still stands as the only known cradle of life. Yet scientists remain driven to uncover potentially habitable worlds beyond our solar system. A recent wave of EU-funded research is aiming to sharpen the tools used to detect Earth-like planets, especially around Sun-like stars, where the signals are faint and easily overwhelmed by stellar activity.
To bridge the gap between discovery and confirmation, researchers are developing a new, compact telescope named PoET — Paranal Solar Espresso Telescope. Built under the EU-funded initiative FIERCE, PoET is designed not to hunt distant planets directly but to study the Sun’s own surface in exquisite detail. The goal is to understand the “noise” produced by stellar activity so scientists can clean it from the data when observing other stars.
The challenge: stellar noise and its disguises
Stars like our Sun are dynamic, with churning plasma and shifting magnetic fields that create dark spots, granulation patterns, and fluctuating spectra. These phenomena can mask the subtle dimming that reveals a planet transiting its star. “The surface of the Sun looks like a boiling pot of water, speckled with darker and brighter regions,” explains Dr. Nuno Santos, a leading Portuguese astrophysicist and the project’s co-lead. “We don’t yet fully understand how to diagnose this noise.”
PoET’s innovative approach is to keep a constant watch on the Sun as a proxy for Sun-like stars, mapping how granulation and related processes affect light. When coupled with spectral data from distant stars, these solar observations should help astronomers separate genuine planetary signals from stellar noise.
PoET, ESPRESSO, and a seamless integration
The PoET telescope, a compact 60-centimeter instrument, will operate at the European Southern Observatory’s (ESO) Very Large Telescope (VLT) site in Chile. During the day, PoET will observe the Sun, analyzing its surface activity in real time. At night, ESPRESSO — the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations — will continue to dissect starlight from distant suns. ESPRESSO is already a backbone instrument for extreme precision spectroscopy, capable of distinguishing minute wavelength shifts caused by orbiting planets.
The collaboration aims to forge a direct connection between solar observations and how we interpret the spectra of distant, Sun-like stars. As Santos notes, linking PoET with ESPRESSO will yield a detailed, evolving chemical fingerprint of the Sun’s atmosphere, revealing how its output changes with surface activity. This information provides a foundational map for filtering stellar noise out of exoplanet observations.
PLATO: a target for cleaner data and happier discoveries
PoET’s work is timed to support the European Space Agency’s PLATO mission, scheduled for launch in 2026. PLATO will use 26 cameras to monitor a million stars, aiming to find Earth-like worlds around Sun-like stars and measure planetary radii to infer density and composition. However, PLATO’s ambitious cataloging relies on pristine data, free from misleading stellar noise. PoET is positioned to deliver just that, helping to maximize the mission’s yield of viable Earth-like candidates.
Researchers hope to begin observations with PoET by the end of 2025, continuing for three years. When combined with PLATO’s pipeline, the approach could dramatically increase the reliability of discoveries and accelerate the timeline for characterizing potentially habitable planets far beyond our solar system.
A broader horizon for space exploration
Beyond PLATO, future missions — including NASA’s Habitable Worlds Observatory and the next generation of European telescopes planned for completion in the 2030s — will benefit from the groundwork PoET and ESPRESSO lay today. By reducing the stellar noise that has long hindered the hunt for Earth-like planets, scientists edge closer to answering one of humanity’s oldest questions: are we alone?
Supported by the European Research Council and EU Horizon funding, this effort underscores Europe’s leading role in the global search for habitable worlds and the ongoing dialogue between ground-based astronomy and space-based exploration.
