How far away is Neptune now?

Last Updated: Today

As of September 15 2023, Uranus is 1,778,039,886 miles (2,860,866,177 kilometers) away from Earth, which is about 19.1237092087378 AU.

Where does this live distance data come from?

I source Neptune’s distance from Earth via the Horizon JPL API. It is a free service provided by NASA’s Jet Propulsion Laboratory (JPL) that offers access to ephemeris (positional) data and related information for celestial bodies, such as planets, asteroids, and comets. The system can be accessed through various interfaces, including a web interface, a telnet interface, and an email interface.

This API contains the precise distance between Neptune and Earth from each day of the next few hundred years.

So I simply created a system to check for today’s date, then go retrieve the accurate distance value directly from NASA’s database. The up-to-date value is then displayed on this page.

How do scientists calculate the real-time distance between Neptune and earth?

Scientists calculate the live distance between Neptune and Earth using a combination of mathematics, astronomical data, and the principles of celestial mechanics.

The positions of Earth and Neptune in their respective orbits are constantly changing due to their elliptical orbits and different orbital periods around the Sun.

Neptune's orbital parameters

Orbital parameters describe the way objects move around in space, such as planets, moons, and satellites. These parameters include the size, shape, and tilt of the orbit, as well as the object’s position and speed within the orbit.

They help scientists understand and predict the paths of celestial bodies, which is crucial for planning space missions, observing astronomical phenomena, and monitoring satellites.

Measure Neptune Earth Ratio (Neptune/Earth) Definition
Semimajor axis (106 km) 4,514.953 149.598 30.178 Half of the major axis of the elliptical orbit
Sidereal orbit period (days) 60,189 365.256 164.79 Time it takes to complete one orbit around the sun
Tropical orbit period (days) 59,799.9 365.242 163.73 Time between two consecutive vernal equinoxes
Perihelion (106 km) 4,471.050 147.095 30.396 Closest distance to the sun in the orbit
Aphelion (106 km) 4,558.857 152.100 29.973 Farthest distance from the sun in the orbit
Synodic period (days) 367.49 Time it takes for the object to reappear at the same point in the sky
Mean orbital velocity (km/s) 5.45 29.78 0.183 Average speed at which the object orbits around the sun
Max. orbital velocity (km/s) 5.47 30.29 0.181 Maximum speed at which the object orbits around the sun
Min. orbital velocity (km/s) 5.37 29.29 0.183 Minimum speed at which the object orbits around the sun
Orbit inclination (deg) 1.770 0.000 Angle between the object’s orbit plane and the ecliptic plane
Orbit eccentricity 0.0097 0.0167 0.581 Measure of how much the orbit deviates from a perfect circle
Sidereal rotation period (hrs) 16.11* 23.9345 0.673 Time it takes for the object to complete one rotation on its axis
Length of day (hrs) 16.11 24.0000 0.671 Time for the planet to rotate once relative to the Sun (solar day)
Obliquity to orbit (deg) 28.32 23.44 1.208 Angle between the object’s rotational axis and its orbital axis
Inclination of equator (deg) 28.32 23.44 1.208 Tilt of the object’s equator relative to its orbit

Neptune at opposition (for the next 3 years)

When astronomer talks about Neptune being at opposition, it means that the ice giant, the Earth, and the Sun are aligned in a straight line, with Earth in the middle. During this time, which lasts for a few weeks, Neptune appears brighter and larger in the sky because it’s at its closest point to Earth in its orbit.

Neptune reaches opposition approximately once a year, providing astronomers and stargazers with an amazing opportunity to observe and admire the ice giant planet.

Below you can find a list of opposition dates for the next 3 years:

Date & Time (PDT)Date & Time (UTC)ObjectRight AscensionDeclinationConstellationMagnitudeAngular Size
TUE, 19 SEP 2023 AT 04:0911:09Neptune23h47m00s2°47’SPisces7.82.4
FRI, 20 SEP 2024 AT 17:0800:08Neptune23h55m20s1°56’SPisces7.82.4
TUE, 23 SEP 2025 AT 05:4512:45Neptune00h03m30s1°06’SPisces7.82.4

Just for fun, how long would it take to reach Neptune via different transportation means

Neptune is the farthest planet in the solar system: the average distance between Earth and Neptune is mind blowing 2.8 billion miles (4.5 billion kilometers), so based on that distance, I have calculated the time it would take to reach the ice giant at the speed of different means of transportation.

• On foot (3 mph): approximately 106,575.34 years
• Bicycle (15 mph): approximately 21,315.07 years
• Horse (galloping at 25 mph): approximately 12,789.04 years
• Motorbike (average speed of 70 mph): approximately 4,539.68 years
• Boat (cruising speed of 23 mph): approximately 13,904.37 years
• Car (60 mph): approximately 5,322.52 years
• High-speed train (200 mph): approximately 1,596.76 years
• Commercial Airplane (575 mph): approximately 556.41 years
• Concorde supersonic jet (1,350 mph): approximately 236.99 years
• SpaceX Starship (projected average speed of 16,777 mph): approximately 19.03 years

Please note this is only for fun and it does not reflect the reality of space travel. This is a simplification and does not account for acceleration, deceleration, or the gravitational influences of celestial bodies which would play significant roles in actual space travel.

Also, these calculations assume constant speed, which is not how actual space travel works. A real trip to Neptune would be faster due to the spacecraft picking up speed from gravitational assists.

Bonus Fact: On average it takes about 4-4.5 hours for light from Neptune to reach Earth.

How far away are the other planets of the solar system?

I have developed a webpage that monitors the real-time distances between Earth and each planet of the solar system:

Written by Tom Urbain

I’ve been fascinated by space and astronomy from a very young age. When I’m not watching space-themed documentaries, movies or TV series, I spend most of my free time in my backyard admiring the planets and galaxies with my telescope.