Other worlds
Exoplanets
An exoplanet is any planet outside our solar system. Astronomers have confirmed thousands of them, ranging from scorching gas giants to small rocky worlds like Earth.
How astronomers find exoplanets
- Method
Transit method
A planet passes in front of its star and dims its light very slightly.
- Method
Radial velocity
A planet's gravity tugs its star back and forth in a rhythmic wobble.
- Method
Direct imaging
Advanced telescopes photograph the planet after blocking the star's glare.
- Method
Gravitational microlensing
A distant planet's gravity briefly magnifies the light of a background star.
The habitable zone
The habitable zone is the range of distances from a star where a rocky planet could hold liquid water on its surface. Being in the habitable zone does not guarantee life, but it is an important starting point for searches.
A few interesting worlds
TRAPPIST-1e
Rocky world in the habitable zone of a small, cool red dwarf.
Kepler-452b
A super-Earth in the habitable zone of a Sun-like star.
Proxima Centauri b
A candidate planet orbiting the closest star to the Sun.
K2-18b
A sub-Neptune whose atmosphere has been probed for water vapor.