A star makes its own light through nuclear fusion, while a planet has no fusion of its own and simply orbits a star, cleared of other debris along its path. Jupiter, the largest planet in our solar system, only reflects sunlight, whereas the Sun, the closest star to Earth, produces its own light and heat.
The core difference
A star generates its own light and heat; a planet orbits a star and produces neither.
- planet — a large, roughly spherical body that orbits a star and has cleared its orbital path: Jupiter is the largest planet in our solar system.
- star — a huge glowing ball of gas that produces light and heat through nuclear fusion: The Sun is the closest star to Earth.
How to tell them apart
The memory hook is the etymology: planet comes from Greek planetes, meaning wanderer, because ancient Greeks noticed a handful of points moving against the fixed backdrop of stars. That fixed backdrop is the stars themselves, which stay in place relative to each other because they are far more distant and simply do not move around a central point the way planets do.
The mix-up sometimes shows up when people call the Sun a planet, or call any bright point in the night sky a star, when it may actually be a planet like Venus or Jupiter reflecting sunlight rather than producing its own.
