Which planet is closest to the Sun?
Mercury is the planet closest to the Sun, at an average distance of about 58 million kilometers. It completes one orbit in just 88 Earth days.
Mercury's orbit is the most oval of all the planets. Its distance from the Sun ranges from about 46 million kilometers at its closest to about 70 million at its farthest. From Mercury's surface, the Sun would look about three times larger than it does from Earth.
Because it is so close to the Sun, Mercury is hard to see from Earth. It appears only low in the sky just after sunset or just before sunrise, and it never strays far from the Sun.
Closest to Earth
Surprisingly, Mercury is also the planet that is closest to Earth on average, and to every other planet. Venus comes nearer to Earth at times, but it also spends long periods on the far side of the Sun, while Mercury always stays relatively close.
Did You Know?
Small changes in Mercury's orbit could not be fully explained by Newton's laws. Einstein's general theory of relativity explained them in 1915, helping confirm his theory.