Neptune’s distance from the Sun is 4.5 billion km; more specifically, it’s 4,503,443,661 km. If you’re still using the Imperial system, that’s the same as 2.8 billion miles.
But this number is actually an average. Like all of the planets in the Solar System, Neptune follows an elliptical orbit around the Sun, so it’s sometimes closer and sometimes further than this average number. When Neptune is at its closest point to the Sun, called perihelion, it’s 4.45 billion km from the Sun. And then when it’s at its most distant point from the Sun, called aphelion, it’s 4.55 billion km from the Sun.
Astronomers also measure distance in the Solar System using a measuring tool called the “astronomical unit”. 1 astronomical unit, or AU, is the average distance from the Earth to the Sun; that’s about 150 million km. So, Neptune’s average distance from the Sun is 30.1 AU. Its perihelion is 29.8 AU, and it’s aphelion is 30.4 AU.
We have written many articles about Neptune for Universe Today. Here’s an article about Neptune’s moons, and here’s an article about how Neptune’s southern pole is the warmest place on the planet.
We’ve also recorded an episode of Astronomy Cast all about Neptune. Listen here, Episode 63: Neptune.