Using clever light-detecting techniques, ExTrA searches red dwarf stars for planets that might support life. By studying tiny dips in starlight, scientists can reveal planetary atmospheres and prepare for deeper exploration with powerful telescopes.
Hidden within ESO’s La Silla Observatory in Chile, a small but powerful telescope is helping astronomers search for Earth-like planets. It is one of three telescopes in the French-led ExTrA project, designed to detect planets orbiting distant stars in the Milky Way and study their environments. But how do these telescopes uncover so much about worlds light-years away?
When a planet passes in front of its star from our perspective, it briefly blocks a tiny fraction of the star’s light — similar to how the Moon darkens the Sun during a solar eclipse. ExTrA focuses on red dwarf stars, which are smaller and dimmer than our Sun. Because these stars emit less light, an Earth-sized planet passing in front of them blocks a more noticeable portion of their brightness, making detection easier.
Beyond simply finding planets, ExTrA also analyzes the starlight passing through their atmospheres. Using spectroscopy, it examines different wavelengths of light to identify possible atmospheric components. The most promising candidates are then studied in more detail using ESO’s Very Large Telescope and, in the future, the Extremely Large Telescope. These powerful instruments could reveal whether these planets have the right conditions to support life — bringing us one step closer to discovering our first cosmic neighbors.
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