For centuries, humans wondered if we’re alone in the universe. Today, thanks to exoplanet discoveries, we know planets orbit stars throughout the galaxy — and some could host life.
What Are Exoplanets?
Exoplanets are planets orbiting stars beyond our Sun. The first confirmed detection came in 1992, when astronomers found planets circling a pulsar. Then, in 1995, the first planet around a Sun-like star was discovered: 51 Pegasi b, a gas giant 50 light-years away.
As of 2025, thousands of exoplanets have been confirmed, with a stunning variety:
- Hot Jupiters, massive gas giants orbiting scorching close to their stars.
- Super-Earths, rocky worlds larger than Earth but smaller than Neptune.
- Earth analogues, in the habitable zone where liquid water could exist.
How Do We Find Exoplanets?
Two main methods revolutionised the search:
- Transit method: when a planet crosses in front of its star, it dims the light slightly, which telescopes like Kepler and TESS measure precisely.
- Radial velocity method: as a planet orbits, it tugs its star back and forth, shifting the star’s light spectrum.
Other techniques, like direct imaging, have also captured photos of large exoplanets.
The Search for Another Earth
Astronomers focus on the habitable zone, or “Goldilocks zone,” around stars where it’s not too hot or cold for water. Planets like Kepler-186f and TRAPPIST-1e excite scientists because they’re Earth-sized and could have the right conditions for life.
Could Life Exist Out There?
Discovering life will likely start with atmospheric signatures: telescopes like the upcoming James Webb Space Telescope look for gases like oxygen or methane, which could hint at biology.
As NASA exoplanet scientist Dr. Sara Seager says: “The discovery of life elsewhere would be the most profound moment in human history.”
A Universe Teeming with Worlds
The Milky Way alone may have billions of Earth-like planets. The quest for exoplanets expands our sense of cosmic possibility — and the dream that we might not be alone.
