How do we find habitable planets?

We start by looking for planets that resemble Earth, the only planet we know of that is inhabited. That means we're looking for planets that are roughly the same size as ours and, like Earth, orbit in their stars' "habitable zones," or at the right distance from their stars —where it's not too hot or too cold — to support liquid water on the planets' surfaces. Planet-hunting missions, such as NASA's Kepler and K2, discovered thousands of planets, or "exoplanets," orbiting distant stars, with several Earth-like candidates. NASA's Transiting Exoplanet Survey Satellite (TESS) searches for Earth-size exoplanets that are much closer to our solar system. Thus, astronomers now can detect solid surfaces, like Earth's, and to probe the atmospheres of these exoplanets. Using telescopes and observatories, astronomers can detect an exoplanet by looking for a small dip in light, called a "transit," shining from a star as the planet orbits in front of it. Once an exoplanet is detected, we can learn a lot about its characteristics. We do this by examining which wavelengths of light are absorbed or reflected as they pass through an exoplanet's atmosphere on their way to our detectors. The James Webb Space Telescope, launched in 2021, is designed to detect minute differences in wavelengths to determine what chemical elements are present in exoplanetary atmospheres. This is a key step toward finding biosignatures and other evidence of habitability. SEEC scientists and engineers are helping design future missions that will help determine if other habitable planets exist and how common they are.

Related Themes: Exoplanet Observations and Missions; Astrobiology, Habitability, and Biosignatures