- 5 Oct in London, Neptune: visible all night. In the south, 38° up, around 00:10. Magnitude 7.8, in Pisces.
- Neptune is in the evening sky 5 Oct – 5 Mar, 10 Sep – 4 Oct, and in the morning sky 23 May – 3 Oct. Brightest on 27 Sep (7.8), closest to the Earth on 27 Sep, 4,319 million km.
- Neptune behind the Sun: 24 March 2027.
Tonight in London
| Rises | 18:12 |
| Sets | 06:15 |
| Best | In binoculars: visible all night |
| Where to look | In the south, 38° up, around 00:10 |
| Constellation | Pisces |
How to find it
Neptune cannot be seen with the naked eye: at about magnitude 7.8 it is well below the faintest visible stars. It takes 165 years to orbit the Sun and stays in the same constellation for more than a decade.
The nearest bright signpost now is Saturn: Neptune is 9° from that planet, a few binocular fields away. Light takes 4.0 hours to reach the Earth from the planet now.
When it shows over the next 12 months
Neptune is in the evening sky 5 Oct – 5 Mar, 10 Sep – 4 Oct, and in the morning sky 23 May – 3 Oct. Brightest on 27 Sep (7.8), closest to the Earth on 27 Sep, 4,319 million km.
Month by month
On the 15th of each month: when the planet rises and sets, its brightness, constellation and distance from the Earth.
| Date | Rises | Sets | Magnitude | Constellation | Distance |
|---|---|---|---|---|---|
| 15 Oct | 17:32 | 05:34 | 7.8 | Pisces | 4,329 million km |
| 15 Nov | 14:29 | 02:29 | 7.8 | Pisces | 4,376 million km |
| 15 Dec | 12:31 | 00:30 | 7.9 | Pisces | 4,447 million km |
| 15 Jan | 10:26 | 22:30 | 7.9 | Pisces | 4,526 million km |
| 15 Feb | 08:25 | 20:33 | 7.9 | Pisces | 4,588 million km |
| 15 Mar | 06:36 | 18:48 | 8.0 | Pisces | 4,616 million km |
| 15 Apr | 05:37 | 17:53 | 7.9 | Pisces | 4,609 million km |
| 15 May | 03:40 | 16:00 | 7.9 | Pisces | 4,567 million km |
| 15 Jun | 01:40 | 14:02 | 7.9 | Pisces | 4,498 million km |
| 15 Jul | 23:42 | 12:05 | 7.9 | Pisces | 4,423 million km |
| 15 Aug | 21:40 | 09:57 | 7.8 | Pisces | 4,358 million km |
| 15 Sep | 19:37 | 07:51 | 7.8 | Pisces | 4,322 million km |
Key dates
The outer planets are best at opposition, when the Earth is between them and the Sun, and hidden for a few weeks around conjunction with the Sun.
| Date | Event | What it means |
|---|---|---|
| 24 March 2027 | Neptune behind the Sun | Conjunction with the Sun: hidden for a few weeks either side. |
| 28 September 2027 | Neptune at opposition | Closest and brightest of the year, rises at sunset and is up all night. |
| 26 March 2028 | Neptune behind the Sun | Conjunction with the Sun: hidden for a few weeks either side. |
| 30 September 2028 | Neptune at opposition | Closest and brightest of the year, rises at sunset and is up all night. |
The Moon next to the planet
Every month the Moon passes Neptune, the easiest way to find the planet. The next close passes:
| Sat 24 Oct | 4.3° |
| Fri 20 Nov | 4.4° |
Where the planet is in the Solar System
The view from above: the Sun in the centre, orbits scaled down. Today Neptune is 4,322 million km from the Earth; over the year the distance ranges from 4,319 million km to 4,618 million km.
What kind of planet
Neptune is the most distant planet in the Solar System, almost 4.5 billion km from the Sun, and the second ice giant, about the size of Uranus but a deeper blue. It has the fastest winds in the Solar System, up to 2,000 km/h, and in 1989 a Great Dark Spot swirled in its atmosphere before vanishing. Its largest moon, Triton, orbits the opposite way to the planet's spin, probably a captured Kuiper Belt object, and nitrogen geysers erupt from its surface.
In binoculars
In binoculars (ideally 10×50 on a tripod) on a dark night Neptune shows as a faint "star" that you will not pick out without a chart. Start from the signpost named on this page and compare over a few nights: Neptune slowly shifts.
In a telescope
From 150–200× a telescope shows Neptune as a tiny (about 2.3″) blue disc with no detail. A larger telescope (from 200–250 mm) on a dark night can show Triton as a faint point beside the planet.
Exploration
Only Voyager 2 has seen Neptune up close, flying past in August 1989, the last stop on its grand tour of the giant planets. It found the Great Dark Spot, narrow rings, six new moons and Triton's geysers. Further missions to Neptune are only being planned.
Name and history
Neptune was the first planet found by calculation rather than by looking. Astronomers noticed that Uranus did not move quite as it should, and the Frenchman Urbain Le Verrier (and, independently, the Englishman John Couch Adams) worked out where an unknown planet pulling on it must be. On 23 September 1846 Johann Galle in Berlin found Neptune within 1° of the predicted spot. Galileo had in fact seen it in 1612–1613 but took it for a star. It is named after the Roman god of the sea.
Facts
| Diameter | 49,244 km |
| Year | 165 Earth years |
| Day | 16 h 6 min |
| Moons | more than 14 |
| Winds | up to 2,000 km/h |
| Mean distance from the Sun | 4.5 billion km |
Other planets
Questions people ask
Can I see Neptune tonight?
In London: visible all night. In the south, 38° up, around 00:10.
When is Neptune in the evening sky?
Over the next 12 months: 5 Oct – 5 Mar, 10 Sep – 4 Oct.
When is Neptune in the morning sky?
Over the next 12 months: 23 May – 3 Oct.
When is Neptune at opposition?
28 Sep 2027: closest and brightest of the year, rises at sunset and is up all night.
How do I tell Neptune from a star?
Planets do not twinkle and shine steadily, while stars twinkle, especially near the horizon. Planets also shift against the stars over a few weeks.
How far away is Neptune?
Today, 4,322 million km. Over the coming year it is closest on 27 Sep (4,319 million km).
Is Pluto the ninth planet?
Not since 2006, when the International Astronomical Union reclassified Pluto as a dwarf planet because it has not cleared its orbit of other bodies. The Solar System has eight planets, and Neptune is the farthest.
Has Neptune gone around the Sun since its discovery?
Yes, exactly once: in 2011 it returned for the first time since 1846 to the point in its orbit where it was discovered.
- Astronomy Engine (Don Cross): planet positions, brightness, conjunctions, oppositions and elongations from VSOP87.
- NASA Planetary Fact Sheets: physical data of the planets.
- NOAA solar calculator equations: twilight times.
Visibility is checked for every day half an hour after evening civil twilight ends and half an hour before morning twilight begins: the planet counts as visible if it is more than 5° above the horizon then.