PLATO Mission: A Promising Planet Hunter
The PLATO mission could become the most successful planet hunter to date. But how is the construction of this telescope progressing at the moment?
In just two years, the long-awaited launch of the planet hunter PLATO (short for PLAnetary Transits and Oscillations of stars) will take place. The telescope will search the universe for Earth-like, rocky planets outside our solar system. Currently, the construction of this promising telescope is in full swing. David Brown, who is involved in the mission and affiliated with the University of Warwick, provides an update on the progress.
Current Status
The European Space Agency (ESA) is responsible for building the planet hunter. “The construction is progressing excellently and is on schedule, so the spacecraft will be ready for launch in December 2026 as planned,” Brown tells Scientias.nl. “One of the key recent advancements is that we now have the first 10 of the 26 cameras ready for installation on the spacecraft. The first camera was installed last month, so we’re really seeing the spacecraft take shape now.”
“Other progress in the construction includes advancements in some of the spacecraft’s electronic components,” continues Brown. “The electronic units that control the cameras, digitize the images, and send them to the onboard data processing system have all been built, calibrated, and tested.”
What Will PLATO Do?
The likelihood is high that PLATO will take to the skies in 2026 without delay. The space telescope will be launched with the new European rocket, Ariane-6, which made its first flight last week at a cost of 4 billion euros. What exactly will PLATO do next? “PLATO aims to find exoplanets around stars that resemble our sun, with orbits long enough to lie in the habitable zone,” says Brown. “One of the main objectives of the mission is to find another pair that is similar to Earth and the Sun. Additionally, the telescope is also designed to carefully and accurately analyze the exoplanets it discovers, such as determining their mass, size, and density.”
In short, the goal of PLATO is to find a planet that closely resembles an ‘Earth twin.’ And Brown explains why an entire mission is dedicated to this.
Searching for Earth-like Planets
“Although we have made many impressive discoveries in the field of exoplanet research, we haven’t found planets that resemble the Earth-Sun pair,” he clarifies. “We have discovered small, rocky planets that are similar to Earth, but these are not around stars that resemble our sun. This means we still don’t know if the way our solar system is structured is normal or not. We think it isn’t, but we only have one example to base our judgment on. By searching for Earth-like, rocky planets with long orbital periods around sun-like stars, we hope to answer this question and improve our understanding of our own solar system. Many questions remain about how planetary systems form and evolve, and about the statistics of these systems. We can only get a complete picture by continuing to search for small, Earth-like, rocky planets.”
Methodology
To find these planets, PLATO will use its 26 cameras. “PLATO does not have different types of instruments,” explains Brown. “The only difference between the 26 cameras is that two cameras can take images faster (every 2.5 seconds instead of 25 seconds).” Therefore, PLATO has 24 ‘normal’ cameras (N-CAMs) and 2 ‘fast’ cameras (F-CAMs). The N-CAMs are divided into four groups of six cameras, with each camera in a group looking in the same direction, but the groups themselves are slightly shifted. “This ensures that PLATO has a huge field of view, better scientific performance, extra safety during malfunctions, and a built-in method to recognize ‘false positive’ signals that could resemble an exoplanet transit,” says Brown. The plan is to observe two specific parts of the sky for two years, one in the north and one in the south. PLATO will use the well-known transit method. In the transit method, the light from a star is measured over an extended period. If a planet passes in front of the star, its shadow causes a small dip in the light intensity, making the presence of the planet detectable. Although this method is known for detecting exoplanets, PLATO has a special trick. The space telescope will continuously stare at individual stars for years, allowing astronomers to detect smaller planets with longer orbital periods.
Life?
In this way, researchers hope to discover if there is a second Earth somewhere in the vast universe. But the big question remains: does life exist elsewhere? “PLATO will not answer that question,” says Brown. “An important step toward coming closer to an answer is to discover how many Earth-like planets likely exist around other stars. We can only find that out by actively looking for such planets.” And that is exactly what PLATO will do. “The planet hunter will soon tell us more about the number of planets similar to Earth in the Milky Way,” states Brown. “Since we assume that Earth-like planets are the most likely candidates for habitation, this information will be crucial in understanding how likely it is that life exists somewhere else.”
Comparison with TESS
PLATO is not the only telescope that detects exoplanets. The Kepler space telescope has already done a lot of work, and currently, the TESS telescope is continuously discovering new planets. How does PLATO differ from TESS? “PLATO differs in several ways,” says Brown. “Firstly, we have many more cameras than TESS (26 compared to 4), and we use them differently. The four cameras of TESS are placed side by side to view a larger part of the sky. In PLATO, the cameras are grouped, with each camera in a group observing the same part of the sky and the same stars. This provides higher quality data (as we can combine the images from the different cameras), offers extra safety in case of malfunctions, and helps us determine if the signals we detect are real. Secondly, our cameras have smaller pixels, allowing us to better distinguish stars that are close to each other. This helps us verify if the planets we think we’ve discovered actually exist. Thirdly, while TESS surveys the entire sky, we will focus on two specific areas and monitor each for two years. This approach is similar to NASA’s Kepler mission and allows us to search for planets with longer orbital periods, something TESS generally can’t detect. Fourthly, while TESS detects potential planets and then asks the broader scientific community to confirm if they are real, PLATO has integrated the follow-up of discovered planets into the mission itself for our primary stars. This allows us to study the planets we find more thoroughly and get a clearer picture of their composition.”
Atmosphere
This means that PLATO will not only search for other worlds. The planet hunter is also intended to further characterize the discovered planets. The goal is to determine the mass, size, and age of exoplanets with unprecedented precision and also investigate their potential atmosphere. For example, researchers hope to infer the presence of an atmosphere or even clouds from the shape of the light dips.
Stars
Furthermore, PLATO is not only a planet hunter. In addition to searching for exoplanets, PLATO will also study stars using various techniques. One of these techniques is asteroseismology, where the vibrations and oscillations of stars are measured to determine their mass, size, and age. “PLATO is therefore also a stellar mission that was designed from the start to combine both scientific areas,” explains Brown. “This approach integrates the study of exoplanets and stellar astronomy, allowing us to achieve the best possible scientific results. With this combination, we can learn much more about the planets PLATO discovers and measure their properties very accurately.”
Looking Forward
The impending launch of the PLATO telescope is a significant step forward in the search for Earth-like exoplanets. Thanks to its advanced technologies, such as asteroseismology and an extensive camera array, PLATO is well-equipped not only to find exoplanets but also to collect detailed information about stars and their environments. These data will enhance our understanding of star and planet formation and might bring us closer to discovering a second Earth. Brown has no doubts. “I am sure we will discover another Earth-Sun pair,” he emphasizes. “And I look forward to seeing what PLATO can mean for astronomy. Additionally, I hope we can go beyond just finding planets. It would be great if we could also detect exomoons, rings, and other detailed information about the planets we discover. Although this will be incredibly challenging, I believe it’s possible and it would be fantastic if we could achieve this.”
