Neptune is often considered to be an unknown entity. Whilst we have made massive strides towards understanding the planet in the past few decades, as of 2021 there’s still only been one space probe that’s directly explored the planet – and that was more than 20 years ago (Voyager 2). One of the main reasons for this is that it’s just so very far away from Earth.
But exactly how fair is Neptune from us, in comparison to other planets like say, Mars? Well, there’s a pretty good reason why Mars is a more realistic place to go to next than Neptune, and it comes down to distance.
How many miles away is Neptune from Earth?
Neptune is actually more than 2.8 billion miles away from us on the planet Earth on average, which is equal to approximately 4.5 billion kilometers away. So, it’s no wonder that we haven’t sent a spacecraft to explore Neptune in recent years.
It’s also worth mentioning that this can vary somewhat depending on the stage Neptune is in its orbit. It can come 0.1 billion miles closer or go 0.1 billion miles further away depending on this, so it does vary across the course of time. This is just one of many great facts about Neptune.
For a good comparison, we can instead use AU, or astronomical units, to know how far Neptune is away from us, and the Sun. One AU is equal to the distance that the Earth is from the Sun; that’s where the measurement comes from. And one AU is equal to 93 million miles. So, this means that Neptune is 29x further away from us than we are to the Sun, which shows just how far away it is.
It’s also very commonly asked just how many light years Neptune is away from the Earth too. The truth here is that it’s not even one full light year away – it’s actually only a little over 4 light hours away from us on Earth. And the reality is that this is just like on Earth where there are 8760 hours in a year, so the reality is that it’s less than 1/2000th of a light year away.
Is Neptune the furthest planet from the Sun?
15 or more years ago, you may have heard that Neptune was actually not the furthest planet from the Sun – Pluto was. However, back in 2006 the IAU (International Astronomical Union) actually downgraded Pluto from being a true planet, and instead graded it as a dwarf planet instead.
And actually, Pluto does occasionally come closer to the Sun than Neptune, as their orbits do meet every few hundred years. However, the two planets will never collide with one another as they’re on a 3:2 orbital ratio, meaning that they’re never at the same point at the same time as one another.
The truth is that even though we have had one spacecraft fly past Neptune, Voyager 2, it could only get some close up shots of the planet. It has no solid surface for us to land on, so there’s no way that we could ever land on the surface to explore the planet some more.
And as Voyager 2 was launched in 1977, and it didn’t reach Neptune until 1989, twelve years is a long wait time. However, what this passing-by did tell us is that Neptune has a great black spot, similar to the one on Jupiter, and its storms are the worst in our solar system.
All in all, Neptune is still the furthest planet away from the Sun, but exactly how far away it is may come as a shock to many people. And actually, when you consider that Mars is only 34 million miles away from us, then it really shows the amount of time it would take to travel to Neptune, which means that it’s more than 50x the journey from our planet.