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Star map showing the path of Neptune against the background stars of Capricornus and Aquarius from 2006 to 2023. Positions are marked for each opposition date. Neptune began the period describing a series of shallow 'hybrid' formations (part zig-zag, part loop) having crossed the ecliptic from North to South in 2003. By the time the planet was South of the Circlet of Pisces, the 'hybrid' loops had transformed into conventional, South-facing loops (the individual 'loops' are not discernible in this chart because of its small scale; instead, each loop appears as an oblique line). Note that, because the angular width of Neptune's loops (about 2º.8 across) are greater than its annual orbital motion against the background stars, each successive loop overlaps (in longitude) with the next. The star map applies to observers in the Northern hemisphere (i.e. North is up); for the Southern hemisphere view, click here. The faintest stars shown on the map have an apparent magnitude of about +4.9. Printer-friendly versions of this chart are available for Northern and Southern hemisphere views. Astronomical co-ordinates of Right Ascension (longitude, measured Eastwards in hrs:mins from the First Point of Aries) and Declination (latitude, measured in degrees North or South of the celestial equator) are marked around the border of the chart. |
The Position of Neptune in the Night Sky:
2006 to 2023
by Martin J. Powell
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Neptune imaged by Mark Lonsdale (Midgard Observatory, Canberra, Australia) in October 2021 using a 14-inch (355 mm) aplanatic SCT reflector telescope fitted with a CMOS camera (Image: Mark Lonsdale / ALPO-Japan) |
From early 1998 through to March 2010, Neptune was positioned in Capricornus, the Sea-Goat. In March 2010, Neptune entered the constellation of Aquarius, the Water Carrier, spending about five months there before returning to Capricornus. In January 2011 it entered Aquarius once more, where it remained until it moved into Pisces, the Fishes, in May 2022.
The apparent magnitude of the planet varied little during the period shown in the star chart: from +7.8 (at opposition) to +8.0 (at superior conjunction). Around all opposition dates shown on the star map, Neptune was due South at local midnight in the Northern hemisphere (due North at local midnight in the Southern hemisphere).
The apparent diameter of the planet (its angular size when seen from the Earth) at opposition throughout the period covered by the star chart was 2".4 (2.4 arcseconds, where 1 arcsecond = 1/3600th of a degree).
In 2010, Neptune completed its first orbit since it was discovered on September 23rd, 1846. The planet was at its 1846 position in the sky (i.e. at the same longitude measured relative to the Earth) on three occasions: in mid-April 2009 (moving direct), in mid-July 2009 (moving retrograde) and in early February 2010 (moving direct). Neptune returned to its discovery position in its orbit (i.e. at the same longitude measured relative to the Sun) in late June 2010.
[Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]
Neptune Conjunctions with other Planets, 2011 to 2023
The following table lists the conjunctions involving Neptune which took place at solar elongations of greater than 20° over the period in question. In several cases, other planets and/or stars were also in the vicinity and these are detailed.
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Neptune conjunctions with other planets from 2011 to 2023 (note that there were no observable planetary conjunctions involving Neptune during 2013 or 2021) The column headed 'UT' is the Universal Time (equivalent to GMT) of the conjunction (in hrs : mins). The separation (column 'Sep') is the angular distance between the two planets, measured relative to Neptune, e.g. on 2017 Jan 13, Venus was positioned 0°.4 North of Neptune at the time shown. The 'Favourable Hemisphere' column shows the Hemisphere in which the conjunction was best observed. Note that observers located close to the Northern/Southern visibility boundary of any given conjunction will have found it difficult or impossible to observe because of low altitude and/or bright twilight. In the 'When Visible' column, a distinction is made between Dawn/Morning visibility and Dusk/Evening visibility; the terms Dawn/Dusk refer specifically to the twilight period before sunrise/after sunset, whilst the terms Evening/Morning refer to the period after darkness falls/before twilight begins (some conjunctions take place in darkness, others do not, depending upon latitude). The 'Con' column shows the constellation in which the planets are positioned at the time of the conjunction. To find the direction in which the conjunctions will be seen on any of the dates in the table, note down the constellation in which the planets are located ('Con' column) on the required date and find the constellation's rising direction (for Dawn/Morning conjunctions) or setting direction (for Dusk/Evening conjunctions) for your particular latitude in the Rise-Set direction table. |
Although any given conjunction takes place at a particular instant in time, it is worth pointing out that, because of the planets' relatively slow daily motions, such events are interesting to observe for several days both before and after the actual conjunction date.
There are in fact two methods of defining a planetary conjunction date: one is measured in Right Ascension (i.e. perpendicular to the celestial equator) and the other is measured along the ecliptic, which is inclined at 23½° to the Earth's equatorial plane (this is due to the tilt of the Earth's axis in space). An animation showing how conjunction dates are determined by each method can be found on the Jupiter-Uranus 2010-11 triple conjunction page. Although conjunctions measured along the ecliptic can be significantly closer, the Right Ascension method is the more commonly used, and it is the one which is adopted here.
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| Eastern Aquarius and the Circlet of Pisces A photograph showing the region of the night sky through which Neptune passed between 2006 and 2023. Stars can be seen down to about magnitude +7.5 (move your pointer over the image - or click here - to see an annotated version of the photograph and click on the thumbnail to see the full-size picture) |
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Finder Chart for Neptune, 2023
During 2023 Neptune could be found several degrees South of the Circlet of Pisces. positioned on or near the border of Aquarius, the Water Carrier, with Pisces, the Fishes.
| The path of Neptune in North-eastern Aquarius/South-western Pisces during 2023, with positions marked on the first day of each month (click on the thumbnail for the full-size image). A Southern hemisphere view can be found here. Where the planet was too close to the Sun to observe, the path is shown as a dashed line. Neptune
reached opposition to the Sun on September 19th 2023
(indicated
on the chart by the symbol Stars are shown down to magnitude +8.5. Right Ascension and Declination co-ordinates are marked around the border, for cross-referencing with a star atlas. Printer-friendly (greyscale) versions of the chart are available for Northern and Southern hemisphere views. Click here to see a 'clean' star map of the area (i.e. without planet path); a printable version can be found here. |
Credits
Copyright Martin J Powell 2006-2022
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) when
it was magnitude +7.8 and its apparent diameter was 2".4 (2.4 arcseconds). The planet was then 28.902
Astronomical Units (4,323 million kms or 2,686 million miles) from Earth.