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Star map showing the path of Neptune against the backdrop of stars in Capricornus and Aquarius from August 2006 to September 2023. Positions are marked for each opposition date. Neptune begins 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 is South of the Circlet of Pisces, the 'hybrid' loops have transformed into conventional, South-facing loops (the individual 'loops' are not discernible in this chart because of the scale of the map; 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, 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 (the above chart will help in finding the general location of the planet throughout the period in question, however a detailed finder chart will be required to pinpoint the planet precisely - see below). |
The Position of Neptune in the Night Sky, 2006 to 2023 by Martin J Powell
From August 2006 to March 2010, Neptune was positioned in Capricornus, the Sea-Goat, where it had been situated since early 1998. In March 2010, Neptune briefly 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 will remain until it moves into Pisces, the Fishes, in April 2022.
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Neptune imaged by NASA's Voyager 2 spacecraft during its August 1989 flyby, showing the previously-unknown Great Dark Spot. Having observed the bland globe of Uranus in 1986, scientists were initially surprised at the high level of activity in Neptune's atmosphere (Image: NASA-JPL) |
Neptune reaches opposition to the Sun (when it is closest to the Earth and brightest in the sky for the year) every 367½ days on average, i.e. about 2½ days later in each successive year. The apparent magnitude of the planet varies 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 is 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 is 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.
Neptune will cross the celestial equator in Pisces in April 2026 (heading North-eastwards and moving direct), in August 2026 (moving retrograde and temporarily heading South-westwards) and again in January 2027 (resuming North-easterly motion, moving direct). For the first time in over 81 years, the planet will then become visible for a longer period of time in the Northern hemisphere than in the Southern hemisphere (it last crossed the celestial equator - as it headed Southwards along the ecliptic - in Virgo in 1944).
Looking further ahead, the planet will continue its Northward motion along the ecliptic until it reaches its most Northerly point in Gemini in 2067, having crossed its perihelion point (i.e. its closest point to the Sun; in this case 29.81 Astronomical Units or 4.46 thousand million kms) in Aries in 2046.
[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, 2011-2015
Viewed from the orbiting Earth, whenever two planets appear to pass each other in the night sky (a line-of-sight effect) the event is known as a conjunction or an appulse. However, not all conjunctions will be visible from the Earth because many of them take place too close to the Sun. Furthermore, not all conjunctions will be seen from across the world; the observers' latitude will affect the altitude (angle above the horizon) at which the two planets are seen at the time of the event, and the local season will affect the sky brightness at that particular time. A flat, unobstructed horizon will normally be required to observe most of them.
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The majority of conjunctions involving Neptune are not spectacular to view because the planet is never visible to the naked-eye. Twilight quickly renders the planet invisible (even through binoculars) such that conjunctions taking place less than about 22° from the Sun are almost impossible to see. When one considers that Venus is always less than 47° from the Sun, whilst Mercury is always less than about 27° from the Sun, it follows that, whenever either of these planets are involved in conjunctions with Neptune, twilight will usually be a problem, the lighter sky diminishing the visual impact of the conjunction.
Because Mercury is only ever seen in twilight, the number of occasions during which it can be seen in conjunction with Neptune is inevitably limited. During the period from 2010 to 2050, there are only ten occasions when Mercury is positioned more than 22° from the Sun at the moment of its conjunction with Neptune. One such occasion takes place on March 22nd 2014, when the planets are positioned 26° West of the Sun. This conjunction is visible from Equatorial and Southern hemisphere latitudes, low down in the Eastern sky before sunrise. However, the planets' low altitude (mostly less than 10° when Neptune is still visible) is likely to prove a problem for many observers. After 2015, another opportunity to see the two planets in conjunction will be in April 2019, when they are 25° West of the Sun; again, this will favour Equatorial and Southern hemisphere observers. In fact, the relationship of Mercury's eccentric orbit to that of the Earth's is such that the planet's most favourable elongations are best seen from the Southern hemisphere. Hence for the most part, Northern hemisphere observers are denied the opportunity of seeing the Sun's closest and furthest planets together in the sky.
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Binoculars will always be required to glimpse Neptune as a pale-blue 'star'. Even when the elongation is favourable, a further problem beckons in that the glare caused by the brighter nearby planet (Venus in particular) makes it difficult to see the much fainter planet beside it. In such instances (e.g. for the Venus-Neptune conjunction of April 12th 2014) binocular observers may find it easier to position Venus just outside the binocular field of view so that Neptune may be more comfortably viewed.
Most conjunctions between Neptune and the other superior planets (Mars, Jupiter, Saturn and Uranus) occur at elongations of less than 90°, when Neptune is below its brightest apparent magnitude in any given apparition. During the period from 2011 to 2015, for example, all the visible conjunctions take place at elongations of less than 46°, Neptune being almost magnitude +8 throughout.
Neptune's most interesting conjunctions take place when the planet is within a few months of opposition, at which times they involve the much brighter planets Mars, Jupiter or Saturn; these events are however very rare. The most recent conjunction of note was between Neptune and Jupiter on December 20th 2009, when Jupiter described its significantly larger planetary 'loop' about one apparent Full Moon-diameter to the South of the outermost gas giant. It was the last of three conjunctions which took place between these planets during that year (more details can be found here). Beyond 2015, Neptune's next favourable conjunctions with superior planets will be with Mars in January 2017, with Jupiter in April 2022 and with Saturn in June 2025.
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In terms of their sizes, their positions within the Solar System and their constituent elements, Uranus and Neptune are often considered to be planetary 'twins'. From the viewpoint of the Earth, faster-moving Uranus 'overtook' Neptune when the two planets were in Sagittarius in July 1993, at which point they were seen in conjunction. This was the first time these planets had been in conjunction since they were discovered (Uranus in 1781, Neptune in 1846). Conjunctions between Uranus and Neptune are rare events indeed, occurring about every 172 years; the next one will take place in the year 2164.
The following table lists the conjunctions involving Neptune which take place between 2011 and 2015 at solar elongations of greater than 22°. In several cases, other planets are also in the vicinity and these are detailed. Note that, because some of the conjunctions occur in twilight, the planets involved may not appear as bright as their listed magnitude suggests.
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Neptune conjunctions with other planets from 2011 to 2015 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 2015 Jan 19, Mars is positioned 0°.2 South of Neptune at the time shown. The 'Fav. Hem' column shows the Hemisphere in which the conjunction will be best observed (Northern, Southern and/or Equatorial). The expression 'Not high N Lats' indicates that observers at latitudes further North than about 50°N will find the conjunction 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 apparitions) or setting direction (for Dusk/Evening apparitions) 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. along 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 conjunction dates measured along the ecliptic are technically more accurate (separations between planets 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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Astronomy Books |
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Atlas of Neptune Garry E. Hunt & Sir Patrick Moore |
Neptune The Planet, Rings & Satellites Ellis D. Miner & Randii R. Wessen |
Uranus, Neptune and Pluto and How to Observe Them (Astronomers' Observing Guides) Richard Schmude, Jr |
NightWatch: A Practical Guide to Viewing the Universe Terence Dickinson "A classic handbook for amateur astronomers" |
Astronomy with a Budget Telescope An Introduction to Practical Observing Patrick Moore & John Watson |
Planetary Nebulae and How to Observe Them (Astronomers' Observing Guides) Martin Griffiths |
DK Smithsonian Nature Guide Stars and Planets Smithsonian Institution |
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Martin J Powell is a participant in the Amazon Europe S.à r.l. Associates Programme, an affiliate advertising programme designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.co.uk, Amazon.de and Amazon.fr |
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Neptune, the most difficult of the 'true planets' to find, photographed here in moderately light-polluted conditions in August 2005, when the planet was in central Capricornus. The planet, barely perceptible in the main picture, appears in the upper left of the rectangular enlargement (move your pointer over the image to reveal the star magnitudes, or click here). When mounted on a tripod, a digital camera fitted with a zoom lens will detect the planet at shutter speeds of only a couple of seconds at higher ISO (film speed) settings. Some photos will even show the planet's characteristic blue-grey colouration. The field of view of the main picture is approximately 2º.3 by 1º.9; that of the inset rectangle is about 0º.43 by 0º.03 (i.e. 25.8 by 18.4 arcminutes). |
Finding Neptune in Your Local Night Sky (General Location)
Where in the night sky should I look for Neptune tonight? In which direction and how high up will it be?
The location of a planet (or any other celestial body) in your local night sky depends upon several factors: the constellation in which it is positioned, your geographical latitude and longitude and the date and time at which you observe. To find a planet in the night sky at any particular date and time, we must know two things: a direction in which to look along the observer's horizon (eg. Southeast, East-Southeast) and an angle to look above the horizon (known as altitude or elevation).
Use the following Javascript program to help find Neptune in your night sky during the year:
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For additional information on the fully-functional version of the program, see here. |
Mini-AstroViewer® is an easy-to-use Java applet which shows the positions of the celestial bodies in the night sky for any location on the globe at any time of the year (Javascript must be enabled in your browser for the program to function). To activate the program, click on the button below (the program will open in a pop-up window). The default location is New York, USA. To select your own location and then find the planets, refer to the 'Finding Neptune ..' box below. An animated tutorial showing how to locate a planet in the night sky using Mini-AstroViewer® can be seen here.
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Finding Neptune in Your Own Night Sky using Mini-AstroViewer®
To set your own location, click on the 'Location' button and click on your approximate position on the pop-up world map. If you know your precise latitude and longitude, you can refine your position by pressing the left/right and up/down arrows to move the cross-hair in 1° increments (to find your latitude and longitude, visit the Heavens Above website, select your country and enter the name of your nearest town or city using the 'Town Search' facility). Having plotted your geographical co-ordinates, click 'OK' and the night sky over your own location will appear in the window, valid for the current time, which is displayed in UT (Universal Time, equivalent to GMT). The applet will initialise displaying the current UT time according to your browser's clock and Time Zone settings (if you would prefer to have the Local Time displayed, use the fully-functional version of the program at Astroviewer.com). The red circle represents the horizon around you; the lower half of the display represents the part of the sky you are facing. The centre of the circle is the point directly above your head (known as the zenith). The ecliptic (the path along which the Sun, Moon and planets will be found) is marked by a red dashed line, passing as it does through the zodiac constellations. The blue dashed line marks the apparent position of the celestial equator, which arcs across the sky from the due East point on the horizon to the due West point. The program plots stars down to magnitude +5.0. The bottom scroll bar rotates the horizon view, allowing for a view in any compass direction; the left-hand scroll bar zooms the sky in or out, and the right-hand scroll bar pans up (to the zenith) or down (to the horizon) whenever the view has been zoomed.
Infomation on a celestial body can be viewed by clicking on the object (in the case of a planet, its magnitude, distance, elongation and apparent diameter). Note that if Neptune's elongation (its angular distance from the Sun as seen from the Earth) is less than about 20°, it will not be visible because it is too near the Sun. Remember that local twilight can affect the visibility of a particular planet, even at elongations greater than 20°, making observation difficult or even impossible. This particularly applies throughout the local summer months at higher latitudes. To find the general location of Neptune in your Night Sky, first see if it is above the horizon at the time you are requesting. If it is visible within the circle, move the bottom scroll bar left or or right to rotate the image until the planet is positioned on the vertical red line (the altitude scale). Zoom in to the area using the left-hand scroll bar where necessary (see animation opposite). The direction of Neptune at the requested time will be indicated at the bottom (W, SW, etc). The altitude of the planet (its angle above the horizon) can be read off on the altitude scale (it is marked at 10° intervals). Hence if it is three notches up, its altitude is 30° at the displayed time (to understand how to determine a planet's altitude in the night sky, refer to the explanatory diagrams below). If Neptune's altitude is less than about 10° it will probably be difficult or impossible to see because of the dimming effect of the Earth's atmosphere and, in town and city locations, the effects of light pollution or skyglow. If
Neptune is not shown within the circle, it is below the horizon
and you will have to wait until after it next rises before you can see
it (provided it is not too near the Sun). To find when it next rises,
click the 'hours forward' button ( If Neptune rises in daylight (i.e. if the Sun is already above the horizon), you will have to wait until after dusk to see it - in which case, 'fast forward' to a time shortly after sunset, then note down the time and direction. This will provide you with the general location of the planet in your Night Sky at the time you have requested. A more detailed 'star hop' will be required to pinpoint the planet precisely - for details, see the 'Finding Neptune' sections below.
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Finder Chart for Neptune, 2012
In early 2011, pale-blue
Neptune
entered the constellation of Aquarius.
During 2012 the planet can be found about 4° South of the star Ancha (
Aqr or Theta Aquarii,
mag. +4.1). To
find Ancha, first locate the 'The Steering
Wheel' asterism in the
Northern section of Aquarius
and 'star-hop' Southwards from it. Use the Mini-AstroViewer®
Java applet above
to help locate Aquarius in your local night sky.
| Finder Chart for Neptune for 2012, with positions marked on the first day of each month (a Southern hemisphere view can be found here). Where the planet is too close to the Sun to be visible, the path is shown as a dashed line. Neptune is positioned in central Aquarius throughout 2012, a short distance South of the star Ancha (Theta Aquarii, magnitude +4.1). Ideally, searches for Neptune should be carried out on Moonless nights, i.e. in the two-week period centred on the New Moon in any given month. In 2012, Neptune reaches opposition to the Sun (when it is brightest in the sky for the year and closest to the Earth) on August 24th, when its apparent magnitude is +7.8 and its apparent diameter is 2".4 (2.4 arcseconds). The planet is then 28.984 AU (4,336 million kms or 2,694 million miles) from Earth. Much of the star field in the chart should be easily contained within a binocular field of view (which typically ranges from 5° to 9°). Stars are shown down to magnitude +8.5. Right Ascension and Declination co-ordinates are marked around the border, for cross-referencing in 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); observers may wish to use the 'clean' star map as an aid to plotting the planet's position on a specific night - in which case, a printable version can be found here. |
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The Current Night Sky over Perth,
Western Australia
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Would you like to see your own town or city shown here?
Requested locations may appear on another planet page (see links below) depending upon the number of requests received by the author at any given time. A list of the night sky locations currently displayed on this website can be seen on the main Naked-eye planets page. The graphic shows the sky at the location indicated when this page was loaded in your browser; if several minutes have since passed, click the 'Refresh' button at the top of your browser (or press the F5 key) to see the current sky. The Night Sky location displayed here is periodically changed by the website author. Additional AstroViewer® Information Mini-AstroViewer® is a lightweight version of AstroViewer®, an interactive night sky map that helps you find your way in the night sky quickly and easily. Due to its intuitive interface, it is well suited to beginners in astronomy. The fully functional, free-to-use version can be accessed at the AstroViewer® website. It has additional features such as a Local Time display, a planet visibility chart for any selected location, a 3D Solar System map, the ability to store user-generated world locations, a 'Find Celestial Body' facility, printing and language options and greater flexibility in the night sky display (see details here). A fully-functional version for offline use can be obtained upon the purchase of a license key, following the download and installation of a test version. AstroViewer® is produced by Dirk Matussek. |
Star Charts showing Positions of the Planets:
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Venus, 2011-2012 |
Mars, 2011-2012 |
Jupiter, 2011-2014 |
Saturn, 2006-2013 |
Uranus, 2006-2018 |
Pluto, 2006-2022 |
Current Position of the Sun and the Brighter Naked-Eye Planets ('Live' Star Map)
Credits
Copyright © Martin J Powell December 2006; revised December 2009, May 2010, January 2011, March 2011
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) repeatedly until the planet
appears over the eastern horizon, then note down the time and direction
this occurs. By clicking the 'minutes/hours forward' buttons (
