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Neptune Ephemeris Calculator
Compute the position of Neptune for any date and time between 1 January 1600 and 30 December 2499 and display the results on an interactive star map.
In Evidence
Neptune
Neptune is the eighth and farthest planet from the sun, and it is the fourth-largest planet in the solar system. It has a diameter of 49,244 kilometers and a mass of 1.02 x 10^26 kilograms, making it about 17 times more massive than Earth. Neptune is an ice giant planet, primarily composed of water, methane, and ammonia, and has a deep, turbulent atmosphere with strong winds and large storms, including the famous Great Dark Spot and the smaller Dark Spot. The planet has a day length of approximately 16.1 Earth hours and an orbital period of 165 Earth years. Neptune has 14 known moons, with the largest being Triton, a captured Kuiper Belt object with a highly inclined and retrograde orbit. Neptune also has a faint and dynamic ring system, which was discovered in 1984 during a stellar occultation. The planet has been explored by only one spacecraft, NASA's Voyager 2, which flew by the planet in 1989, providing the most detailed images and data of the planet and its moons to date.
Neptune is currently in the constellation of Aquarius.
The current Right Ascension of Neptune is 23h 42m 00s and the Declination is -03° 18’ 26” (topocentric coordinates computed for the selected location: Greenwich, United Kingdom ). The current magnitude of Neptune is 7.75 (JPL).
Today's rise, transit and set times of Neptune from Greenwich, United Kingdom (all times relative to the local timezone Europe/London):
- Neptune is below the horizon from Greenwich, United Kingdom .
- Given its current magnitude, Neptune is visible with the help of a binocular with a 30-40mm aperture, easy with a small telescope.
- Go to interactive sky chart
If you need to access this information frequently for your observations, you can create a simple customized Quick Access page, so that you can easily bookmark it in your browser favorites or add a shortcut to your mobile phones' home screen.
Neptune Position and Finder Charts
Below we provide Neptune finder charts showing where the object is right now in the sky with respect to the brightest stars. The first finder chart has a field of view of 50 degrees, while the second one has a field of view of 10 degrees. Click on each finder chart to access a full screen interactive Online Planetarium.
Higher precision deep sky finder chart, 60 arcmin wide, showing where Neptune is right now. Click on the image to see a more detailed fullscreen tracker view.
Also check out Where is Neptune?, a page that provides all the information needed to find Neptune in the sky and additional links to sky charts.
Neptune Distance from Earth
The distance of Neptune from Earth is currently 4,455,818,381 kilometers, equivalent to 29.785306 Astronomical Units. Light takes 4 hours, 7 minutes and 43.0103 seconds to travel from Neptune and arrive to us.
The following chart shows the distance of Neptune from Earth as a function of time. In the chart the distance data is measured in Astronomical Units and sampled with an interval of 1 day.
The value of the reported distance might be somewhat inaccurate around the times of closest approach for objects passing extremely close to Earth. The value of the distance of Neptune from Earth is also available as a real time updated value in the Live Position and Data Tracker.
Closest Approach of Neptune to Earth
Between 1 January 1600 and 30 December 2499, the closest approach of Neptune to Earth happens on Thu Nov 8 2373 at a distance of 28.806366 Astronomical Units, or 4,309,370,997 kilometers:
NOTE: values for the closest approach are computed with a sampling interval of 1 day.
Neptune Brightness and Light Curve
The following chart is the predicted light curve (visual magnitude as a function of time) of Neptune, according to the most recent ephemerides data. Magnitude data is sampled with a 2 days interval and there might be inaccuracies for objects changing brightness very rapidly during the course of a few days. For comets there could be large discrepancies between the observed and predicted brightness because of their highly dynamic behaviour.
Neptune Physical Data
The following shows the known values of the most important physical parameters of Neptune. Source: JPL Small-Body Database
| Physical Parameter | Value | Relative to Earth |
|---|---|---|
| Diameter | 49244 km | 3.8647 |
| Mass | 102.41 x 1024 kg | 17.1478 |
| Density | 1.638 gr/cm3 | 0.2971 |
| Escape Velocity | 23.56 km/s | 2.1055 |
| Sideral Rotation | 16.1100 hours | 0.6731 |
| Absolute Magnitude | -6.87 | |
| Geometric Albedo | 0.41 |
Neptune 15 Days Ephemeris
The following table lists the ephemerides of Neptune computed for the past and next 7 days, with a 24 hours interval. Click on each row of the table to locate Neptune in our Online Planetarium at the chosen date.
| Date | Right AscensionR.A. | DeclinationDec. | MagnitudeMag | Apparent DiameterDiameter | Constellation |
|---|---|---|---|---|---|
| 2023 Dec 04 | 23h 41m 59s | -03° 18’ 47” | 7.74 | 2.3” | Aquarius |
| 2023 Dec 05 | 23h 41m 58s | -03° 18’ 47” | 7.74 | 2.3” | Aquarius |
| 2023 Dec 06 | 23h 41m 58s | -03° 18’ 46” | 7.74 | 2.3” | Aquarius |
| 2023 Dec 07 | 23h 41m 58s | -03° 18’ 43” | 7.74 | 2.3” | Aquarius |
| 2023 Dec 08 | 23h 41m 58s | -03° 18’ 41” | 7.75 | 2.3” | Aquarius |
| 2023 Dec 09 | 23h 41m 58s | -03° 18’ 37” | 7.75 | 2.3” | Aquarius |
| 2023 Dec 10 | 23h 41m 59s | -03° 18’ 33” | 7.75 | 2.3” | Aquarius |
| 2023 Dec 11 | 23h 41m 59s | -03° 18’ 28” | 7.75 | 2.3” | Aquarius |
| 2023 Dec 12 | 23h 42m 01s | -03° 18’ 20” | 7.75 | 2.3” | Pisces |
| 2023 Dec 13 | 23h 42m 02s | -03° 18’ 14” | 7.75 | 2.3” | Pisces |
| 2023 Dec 14 | 23h 42m 02s | -03° 18’ 06” | 7.75 | 2.3” | Pisces |
| 2023 Dec 15 | 23h 42m 02s | -03° 17’ 57” | 7.75 | 2.3” | Pisces |
| 2023 Dec 16 | 23h 42m 05s | -03° 17’ 48” | 7.76 | 2.3” | Pisces |
| 2023 Dec 17 | 23h 42m 06s | -03° 17’ 38” | 7.76 | 2.3” | Pisces |