Which planet is closest to the Sun?

The planet closest to the Sun is Mercury. It orbits the Sun at a distance of about 58 million kilometers. Because it’s so close, it moves very quickly—completing one orbit in just 88 days. Mercury’s surface is rocky, full of craters, and has almost no air. Temperatures vary wildly, from around 430°C during the day to -180°C at night. Even though it’s small, Mercury has a strong core made mostly of iron. Scientists study it to understand how rocky planets like Earth formed billions of years ago from leftover materials in space.