Sara Seager

Water is the gold standard for life. We search for its traces on Mars, in icy moons, and in the atmospheres of distant planets. But what if life doesn't need water? On a warm rocky exoplanet with a thin atmosphere, water would evaporate within hours.

In 2023, the James Webb Space Telescope turned its gaze toward a distant star in the constellation Virgo. Orbiting it is HAT-P-26 b, a warm Neptune, a world with a mass of 18.6 Earths and a radius of 6.33 Earths. The planet transited across the star's disk, and at that moment its atmosphere became briefly visible.

Eavesdropping on a distant planet's atmosphere is hampered by the star's noise. In the TRAPPIST-1 system, astronomers used a planet-"bug": TRAPPIST-1 b — an airless neighbor that records only the interference.

Astronomers listen to starlight using spectroscopy: they spread it into a rainbow and read the dark 'voices' of chemical elements. But the very cool star TRAPPIST-1 didn't sound as the models predicted: water and iron were barely audible, though there should be plenty.

NASA's TESS space telescope monitors thousands of stars, catching the moment when a planet crosses its star's disk — the star's light dims slightly. That's how astronomers spotted two planets orbiting stars similar to our Sun. One, TOI-883 b, completes an orbit in ten days; the other, TOI-899 b, takes nearly thirteen.