What Are Planets Made Of?

June 8, 2026

Measure a planet's size and weight, and you can guess what it's made of — rock, water, or gas. Here's the simple trick scientists use.

Inside KOI-351: A Family of 8 Planets
Far away in the Milky Way, a star called KOI-351 has eight planets orbiting around it — just like our own Sun! Scientists are studying one of those planets, KOI-351 g, to learn more about how entire families of planets are built.
How Did We Find GJ 4274 b?
GJ 4274 b is a super-Earth just 23.6 light-years away, and scientists found it without ever seeing it directly. They tracked tiny wobbles in its star's light to reveal a speedy world that completes one full year in less than two Earth days!
Could HD 40307 g Be Friendly to Life?
About 42 light-years away, a planet called HD 40307 g sits in the zone around its star where liquid water could exist. Scientists can't visit it yet, but the clues they've found make it one of the most interesting worlds to watch when searching for life.
Meet GJ 887 e: A Newly Found Rocky World
Scientists confirmed a new rocky planet called GJ 887 e in 2026, and it is one of the closest exoplanets to Earth ever found. It is a little bigger than our planet, blazing hot, and orbits its star in just over four days — making it a wild world worth learning about.
Proxima Cen d: A World 4.2 Light-Years From Earth
Proxima Cen d is a tiny planet orbiting the closest star to our Sun, just 4.24 light-years away. Scientists found it by watching the star wobble — but what this strange little world is actually like remains a mystery.