As of now, 5,788 exoplanets have been confirmed across 4,326 star systems, with a majority being gas giants or Super-Earths. Only 210 qualify as 'Earth-like' in size and mass. Most of these discoveries have occurred around M-type (red dwarf) stars, with no Earth-like planets found in the habitable zones of sun-like stars.
The limitations of current observatories hinder the detection of Earth-sized planets with longer orbital periods. The European Space Agency's (ESA) upcoming PLAnetary Transits and Oscillations of stars (PLATO) mission, slated for launch in 2026, aims to address this gap by surveying up to 1 million stars over four years.
Led by Andreas F. Krenn from the Austrian Academy of Sciences, a recent study published in Astronomy & Astrophysics outlines PLATO's potential to detect biosignatures on Earth-like planets. These biosignatures, including gases like oxygen and methane, are indicators of life.
The study emphasizes the challenges faced by astronomers, as the signals produced by Earth-like planets are exceedingly small. The transit method, which has confirmed over 4,300 exoplanets, requires precise measurements of light curves for signs of transits. Existing instruments struggle to detect the minute changes in brightness caused by these planets.
PLATO will employ a multi-telescope approach with 26 cameras, enabling it to continuously monitor the same area of the sky for two years. This advanced photometric instrument is expected to detect transits from Earth-like planets with unprecedented accuracy.
The research team modeled PLATO's observational capabilities using data from NASA's Solar Dynamics Observatory. Their findings indicate that PLATO can reliably detect transit signals for bright stars, significantly enhancing the potential for measuring the sizes of Earth-like planets.
Alongside PLATO, next-generation instruments such as the James Webb Space Telescope and the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL) telescope will further advance the search for exoplanets and their atmospheres. These missions are poised to transform our understanding of habitable worlds beyond our solar system.