# How far away is Neptune right now? > Neptune's distance from Earth, live. The farthest planet, found by mathematics, with the fastest winds of any world, visited only once. HTML: https://www.theuniversecounts.com/solar-system/planets/neptune Numbers as of 2026-10-31 03:42 UTC. Live ones keep changing on the HTML page. Right now Neptune is about 4.3 billion kilometres from Earth, and the gap changes every second. A radio message, moving at the speed of light, needs 4 hours to cross it. Neptune is the eighth and farthest planet from the Sun, a blue ice giant found by calculation before it was seen. Its distance from us swings between 4.3 billion and 4.7 billion kilometres. The next close approach is on 27 September 2027. - Time until Neptune's next close approach to Earth: 331 d 13 h 41 m 25 s - Temperature of Neptune at the 1 bar level: -201 °C - Time since Neptune was discovered: 180 y 37 d 3 h - Time since Voyager 2 flew past Neptune: 37 y 66 d 17 h ## The farthest planet What is Neptune? Neptune is the eighth planet from the Sun, and the farthest. It circles about 30 times as far out as Earth does. Even sunlight needs 4.2 hours to get there. NASA says high noon on Neptune would look like dim twilight to us. Like Uranus, it is an ice giant. Most of it is a hot, dense fluid of water, methane and ammonia over a small rocky core. Above that is a deep atmosphere of hydrogen and helium, with no solid surface beneath it. Scientists think an ocean of very hot water may lie under the cold clouds, kept from boiling by the crushing pressure. Neptune is about 3.9 times as wide as Earth, and about 59 Earths would fit inside it. It is a little narrower than Uranus but heavier, with 17 times Earth's mass. Of the giant planets, it is the densest. Methane in its air takes the red out of sunlight, so Neptune looks blue. ## Why the distance keeps changing The next close approach Earth and Neptune both circle the Sun, like runners on a track. Earth runs fast on an inside lane. Neptune is on the outermost lane of all, and moves so slowly that Earth passes it about once a year. Each time, Earth lies between the Sun and Neptune, and the two planets are as close as they get. Astronomers call this line-up an opposition. Half a year later Neptune is beyond the Sun, and the gap has grown by roughly the width of Earth's own orbit. Neptune has crept on a little in the meantime. So the meetings come about every 367 days, a couple of days later in the calendar each year. The clock on this page counts down to the next one, on 27 September 2027. Neptune is so far away that the swing hardly matters. Even at its nearest, it is about 29 times as far from us as the Sun is. ## A hello that takes hours Right now Radio waves are a kind of light, and nothing travels faster. Even so, a message to Neptune needs 4 hours at today's distance. An answer needs as long again to come back. Only one spacecraft has ever been there. Voyager 2 skimmed over Neptune's cloud tops on 25 August 1989, the closest of all its planet flybys. It found a restless world: white clouds of frozen methane, fierce winds and a great dark storm. The team boosted the colours of many of its pictures to bring out the clouds, so Neptune looked a deeper blue than it is. Re-processed in 2024, it looks much like Uranus. It also passed Triton, Neptune's largest moon, and saw geysers of icy material rising from its frozen surface. No spacecraft has been back since. Almost everything we know of Neptune up close comes from those few days. ## Found by mathematics 23 September 1846 Neptune is the first planet found by calculation rather than by searching the sky. Uranus was not moving quite as astronomers expected. Something unseen seemed to be pulling on it. The French mathematician Urbain Le Verrier worked out where an unknown planet would have to be, and how heavy, to explain the drift. He sent his prediction to Johann Galle at the Berlin Observatory. Galle found Neptune on his first night of searching, on 23 September 1846. Its largest moon, Triton, was found a few weeks later. Galileo had seen it long before, in 1612 and 1613, but took it for a star. Neptune takes about 165 Earth years to go once round the Sun. That is about 2.2 human lifetimes. So only in 2011 did it finish its first full lap since Galle saw it. Its tilt is close to Earth's, so it has real seasons, each lasting about 41 years. Its day is short by comparison. With no ground to stand on, a day there is one turn of the planet: 16 h 06 m 36 s. ## Winds and cold Where the air presses like ours Neptune has no surface to stand on, so scientists take its temperature where its air presses as hard as ours does at sea level. There it is about -201 °C. Earth's average is 15 °C. Yet this cold, dim world has the fastest winds of any planet. NASA calls it the windiest world in the solar system. Clouds of frozen methane race across it at up to about 580 metres per second. That is about 2.3 times as fast as an airliner, and about 1.7 times the speed of sound in our air. Earth's strongest winds don't come close. All this on a planet that gets so little energy from the Sun. Its winds even outrun Jupiter's, though Jupiter is far nearer the Sun. ## FAQ ### How far away is Neptune right now? About 4.3 billion kilometres, from the centre of Earth to the centre of Neptune. The number on this page is live. Between 1900 and 2100 it swings between 4.3 billion and 4.7 billion kilometres. ### Can you see Neptune without a telescope? No. NASA says it is the only planet in our solar system not visible to the naked eye. You need a telescope, and to know where to look: the panel under the live distance shows where it is right now. ### Is Neptune the coldest planet? Not quite. Where the air presses as hard as ours at sea level, Neptune is about -201 °C and Uranus about -197 °C. But higher up, NASA says, Uranus gets colder than Neptune in places, down to -224 °C. ### How many moons does Neptune have? 16 known moons, as of October 2026. The largest, Triton, circles Neptune the opposite way to the planet's spin. It is the only large moon in the solar system that does, so it may once have been a separate world that Neptune captured. ### How long does it take Neptune to orbit the Sun? A year on Neptune, one trip round the Sun, lasts about 165 Earth years. Since it was found on 23 September 1846, it has gone round only once, finishing that lap in 2011. ### How long is a day on Neptune? One turn takes 16 h 06 m 36 s. Neptune has no ground, so its day is counted as one turn of the planet. A single Neptune year holds about 90,000 of those days. ## Related - [Uranus](https://www.theuniversecounts.com/solar-system/planets/uranus.md) - [Voyager 2](https://www.theuniversecounts.com/solar-system/spacecraft/voyager-2.md) - [Planets](https://www.theuniversecounts.com/solar-system/planets.md) Neptune was found with mathematics first, and only then with a telescope. What else might be out there, waiting for someone to work out where to look? ## Sources - Average length of one season on Neptune (a quarter of its year) (Measured, with error): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html); [NASA Science: Neptune Facts](https://science.nasa.gov/neptune/neptune-facts/) - Average surface temperature of Earth (Measured, with error): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Average time between Neptune's close approaches to Earth (synodic period) (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Earth's average distance from the Sun in kilometres (Measured): [NASA: Earth: Facts](https://science.nasa.gov/earth/facts/) - Earth's diameter at the equator (Measured): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Equatorial diameter of Neptune (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Fastest wind speed on Neptune (Measured, with error): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html); [NASA Science: Neptune Facts](https://science.nasa.gov/neptune/neptune-facts/) - Largest distance between Earth and Neptune, 1900 to 2100 (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Length of a solar day on Earth (Measured): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Length of a year on Neptune (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Length of one turn of Neptune (sidereal day) (Measured, with error): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Lowest temperature in Uranus's atmosphere (Measured, with error): [NASA Science: Uranus Facts](https://science.nasa.gov/uranus/facts/); [NASA NSSDCA: Uranus Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/uranusfact.html) - Mass of Neptune (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Mass of the Earth (Measured): [NASA NSSDCA: Earth Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) - Neptune's average distance from the Sun (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Neptune's distance from Earth (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Number of known moons of Neptune (Measured): [NASA: Moons: Facts](https://science.nasa.gov/solar-system/moons/facts/) - Smallest distance between Earth and Neptune, 1900 to 2100 (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Speed of light in a vacuum (Measured): [BIPM: SI defining constants](https://www.bipm.org/en/measurement-units/si-defining-constants) - Speed of sound in air at 20 °C (Measured, with error): [NASA Glenn Research Center: Speed of Sound Interactive](https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/speed-of-sound-interactive/); [NASA Glenn Research Center: Specific Heats - cp and cv](https://www1.grc.nasa.gov/beginners-guide-to-aeronautics/specific-heats-cp-and-cv-1/); [BIPM: SI defining constants](https://www.bipm.org/en/measurement-units/si-defining-constants) - Temperature of Neptune at the 1 bar level (Measured, with error): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html) - Temperature of Uranus at the 1 bar level (Measured, with error): [NASA NSSDCA: Uranus Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/uranusfact.html) - Time since Neptune was discovered (Measured): [NASA NSSDCA: Neptune Fact Sheet](https://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html); [NASA Science: Neptune Facts](https://science.nasa.gov/neptune/neptune-facts/) - Time since Voyager 2 flew past Neptune (Measured): [NASA: Voyager Fact Sheet](https://science.nasa.gov/mission/voyager/fact-sheet/) - Time until Neptune's next close approach to Earth (Measured): [National Astronomical Observatory of Japan (NAOJ): ほしぞら情報 2027年9月](https://www.nao.ac.jp/astro/sky/2027/09.html) - Typical cruising speed of a long-haul airliner (Estimated): [EUROCONTROL: Aircraft Performance Database: B789 (Boeing 787-9)](https://contentzone.eurocontrol.int/aircraftperformance/details.aspx?ICAO=B789); [EUROCONTROL: Aircraft Performance Database: A388 (Airbus A380-800)](https://contentzone.eurocontrol.int/aircraftperformance/details.aspx?ICAO=A388) - World average life expectancy at birth in 2024 (Measured, with error): [United Nations, Department of Economic and Social Affairs, Population Division: World Population Prospects 2024: Summary of Results](https://population.un.org/wpp/assets/Files/WPP2024%5FSummary-of-Results.pdf)