Exoplanets: Worlds Beyond Our Solar System
TL;DR Summary
We have discovered over 5,000 planets orbiting other stars. What are these strange new worlds like?
The Discovery Explosion
For most of human history, we only knew of the planets in our own solar system. That changed in 1995 with the discovery of 51 Pegasi b, the first confirmed exoplanet orbiting a sun-like star. Since then, the Kepler and TESS space telescopes have discovered thousands more.
Strange New Worlds
Exoplanets come in a bizarre variety of types that don't exist in our solar system:
- Hot Jupiters: Gas giants orbiting extremely close to their host stars, with temperatures hot enough to melt iron.
- Super-Earths: Rocky planets larger than Earth but smaller than Neptune.
- Water Worlds: Planets covered entirely by deep oceans.
The Search for Earth 2.0
The ultimate goal of exoplanet hunting is to find a rocky planet in the "habitable zone" of its star—the region where temperatures allow liquid water to exist on the surface. While we have found several candidates, we are still searching for a true Earth twin.