The elements that make up stars, mostly hydrogen and helium, are also found on planets.
Jupiter, Saturn, and Uranus’s atmospheres, for example, are also mostly hydrogen and helium.
Earth’s matter is mostly carbon-based, and carbon is found in stars, particularly old-age white dwarfs.
Stars, however, grow big enough to spark nuclear fusion and planets don’t.
Consequently, planets do not shine with their own light, but reflect the light of a local star, and are cooler than stars.
Planets “wander” across the sky, meaning that while stars are steadfast in relation to each other, planets appear to travel through the constellations.
Planets are less massive and therefore less dense than stars.
Orbiting asteroids meet some of the criteria for planets, which is why they are sometimes called minor planets.
