Are there planets similar to Earth? Do they orbit stars like our sun? Which type of parent stars and planets often go together? Which planets have an atmosphere that we can further investigate? From late 2026 onwards, the PLATO space telescope will search for answers.
The Netherlands is making important contributions. Eleven PLATO cameras have been tested at SRON in Groningen in recent years. And planetary scientists at SRON and Dutch universities have been pioneering methods for years to get the most out of the data from PLATO and its successors.
In early September, PLATO arrived by transport ship at ESA’s ESTEC research centre in Noordwijk to be fitted with solar panels and sunshields: the final step before launch.
ESA’s PLATO (PLAnetary Transits & Oscillations of stars) telescope will continuously observe around 250,000 stars. Scientists expect that most of these stars have planets and that PLATO will help us discover thousands of them.
Long-term observation, catching rare planetary transits
Every time a planet passes in front of its parent star as seen from our perspective, PLATO detects a dip in the amount of light that the star shines in our direction: the “planetary transit”. PLATO will continuously observe the same stars for years. This increases the likelihood of discovering more Earth-like planets. Planets like our Earth are small and take a long time to orbit their star. Viewed from a distant planet, our Earth also passes in front of the Sun only once a year as a planetary transit.
Observing a large section of the sky
PLATO has 26 cameras, each covering a small section of the sky. Together, they provide a wide field of view of 2,250 square degrees: a section of the starry sky as large as 10,000 full moons.
Planet dips or instrument dips?
The scientists behind PLATO have spent a great deal of time developing computers that can recognise which dips are caused by stars flickering rather than planets. Through extensive testing, they also know all the effects that small changes in the telescope itself have on the measurements. For example, small movements caused by heat and cold. At SRON in Groningen, the operation of eleven cameras has been tested in a vacuum at a whole range of temperatures that they will soon have to endure in space.
Planetary evolution
PLATO provides astronomers worldwide with a new catalogue of planets and their parent stars. From this, we can learn about the different types of planets that exist, the types of stars they orbit, and what kind of planetary system can exist at which stage of a star’s life.
PLATO can also observe starquakes during its long observations: “astroseismology”. Scientists can deduce from these starquakes how large, heavy and old a star is.
Atmosphere alert: will cloud cover cause a mini peak?
Larger gas giants such as Jupiter, when they almost disappear behind a star, could actually cause a spike in the light measurement. Suppose they have a cloud cover that briefly reflects some extra starlight in our direction? What do spikes say about the presence of an atmosphere?
Zooming in on planets with atmospheres with ARIEL
Dutch researchers are playing a pioneering role in the young research field of exoplanet atmospheres. They combine observations of stellar quakes, dips and short-lived peaks with computer simulations.
This will enable them to identify the most promising planets among all the PLATO discoveries that may have an atmosphere. This is important for follow-up research with ESA’s ARIEL telescope, which will search for atmospheres in a promising selection from the PLATO observations starting in 2029.
PLATO was developed in a collaboration between Germany, France, Italy, Spain, the Netherlands, Belgium and other countries.