PLATO Opens Its Doors for Complementary Science

31 August 2026

ESA’s PLATO mission has set itself an ambitious goal: to find and characterise potentially habitable planets around nearby, bright, Sun-like stars. Yet, as PLATO prepares for launch, scientists across Europe and around the world are already planning how to use its unique capabilities for an even broader range of complementary science.

ESA’s inaugural Announcement of Opportunity in spring 2026 invited scientists worldwide, whether affiliated with the mission or not, to propose observations that complement PLATO’s core science. The call was open to a broad range of topics, from small bodies in our Solar System to extragalactic phenomena such as Active Galactic Nuclei. Successful proposals were selected following a rigorous technical assessment and scientific peer review by PLATO’s Time Allocation Committee, which brought together experts from across astronomy. Based on these recommendations, ESA’s Director of Science, Professor Carole Mundell, has now approved the first set of PLATO Guest Observer programmes.

“Together with the mission’s core science goals, these innovative ideas demonstrate how PLATO’s combination of a wide field of view, high photometric precision, and continuous long-duration observations will enable discoveries across many areas of astrophysics, opening new opportunities for the scientific community to deepen our understanding of planets, stars, and the Galaxy,” says Professor Mundell.

A unique opportunity

PLATO’s primary goal is to discover and characterise long-period planetary systems around Sun-like stars while determining their host stars properties and ages for a complete picture of their evolution over time. Yet, the mission’s design to stare continuously at the same regions of the sky for at least two years opens opportunities far beyond its core science. The Guest Observers Programme gives the worldwide scientific community access to the mission’s capabilities, allowing researchers to propose investigations that complement and expand PLATO’s primary goals. 

"This fantastic response to our call from the community, both in volume and in scientific quality, is a major step forward in our preparations for launch. We can now proceed to incorporate these Guest Observer targets into our long-term plan with a focus to maximise the output from the payload during the routine in-orbit science operations phase," adds Laurence O'Rourke, PLATO Science Operations Development Manager.

Tracing the origins and ends of planetary systems

Some of the selected projects stay close to the mission’s theme of exoplanets, but focus on stars very different from our Sun today, seeking to understand how planetary systems form and evolve in their youth. To this end, some teams seek to use PLATO to study very young stars still surrounded by the discs of gas and dust from which planets emerge. By monitoring these systems continuously for years, scientists aim to watch the processes that shape newborn planetary systems and identify the environments in which planets first assemble. 

Others aim to search for planets orbiting stellar types that have been less explored so far, helping to build a more complete picture across the stellar family tree. For example, several projects will also investigate what happens to planets at the end of a star’s life, studying white dwarfs and the remnants of their planetary systems. Together, these observations help connect theories of planet formation and evolution with the rich diversity of planetary systems seen throughout the Galaxy.

Understanding a wide range of stars from the inside out

Other selected projects turn PLATO’s attention towards the nature of stars themselves, from young active stars and multiple-star systems to evolved giant stars. With at least two years of continuous observations, researchers will be able to study stellar variability, binary interactions, and asteroseismology - probing conditions deep inside stars with a level of detail not previously possible for such large samples. 

Some of the selected programmes will investigate how stars transport energy, angular momentum, and chemical elements through their interiors. Others will explore the role of magnetic fields, study massive stars that may eventually explode as supernovae, or examine how interactions in binary systems alter stellar evolution. Together, these studies are expected to improve our understanding of how stars form, age, and ultimately shape their cosmic surroundings.

Exploring the history of our Galaxy and beyond

PLATO’s observations will also extend beyond individual stars. Several programmes will target globular clusters, among the oldest stellar systems in the Milky Way. By measuring the internal properties of stars within these clusters, astronomers hope to better understand the assembly history of our Galaxy and the evolution of some of its oldest stellar populations.

Other programmes will look beyond the Milky Way altogether, investigating extragalactic phenomena in the Large Magellanic Cloud. These may include unusual objects such as interacting binary stars and accreting systems that can lead to signficant brightness variations. PLATO’s continuous monitoring will help them to unveil physical processes that cannot be captured through short-duration observations alone.

One observatory, many discoveries

“The breadth of the selected Guest Observer projects highlights one of PLATO's great strengths: while the mission was designed to discover and understand planets like our own, the same observations can also help answer a remarkably diverse range of astrophysical questions, showcasing the versatility of the mission,” comments Maximilian Günther, PLATO Project Scientist.

While PLATO's search for Earth-like worlds remains its core science objective, the mission will support far more than exoplanet research alone. From the dusty birthplaces of planets to the interiors of stars, from ancient globular clusters to interacting binary systems, the first Guest Observer projects showcase the breadth of science that can be pursued alongside the mission's primary goals.

As PLATO prepares for launch, the selected proposals offer a glimpse of the discoveries that may emerge once the mission begins its long watch of the sky in 2027.