HAT-P-11b is smallest exoplanet known to host the life-friendly molecule
David A. Aguilar/CfA
The smallest, coolest exoplanet known to host water is roughly the size of Neptune, astronomers report in the Sept. 25 Nature. Previously, researchers had found water only on exoplanets that are about the size of Jupiter. The planet HAT-P-11b is just over four times as wide as Earth.
Jonathan Fraine, an astronomer at the University of Maryland in College Park, and colleagues discovered the water after a year and a half of observations with the Hubble, Spitzer and Kepler space telescopes.
Gases such as water vapor in a planet’s atmosphere leave their mark by absorbing specific frequencies of light. When HAT-P-11b comes between Earth and its star, the planet’s atmosphere filters out some of the starlight. The astronomers detected water by observing infrared light that