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The path of Jupiter against the background stars of Pisces, Aries, Taurus and Gemini from May 2011 to July 2014, with positions marked on the 1s of each month. Periods of invisibility (i.e. when the planet is too close to the Sun, or passes behind it) are indicated by a dashed line; hence the planet becomes lost from view (in the evening sky) in late April 2012 and becomes visible again (in the morning sky) in early June 2012. The chart shows the changing shape of a planet's apparent looping formation as it moves through the zodiac. Being positioned South of the ecliptic during 2011-12, Jupiter describes a Southwards-facing loop in Aries, then a hybrid formation (half loop, half zig-zag) a year later in Taurus. As the planet crosses the ecliptic (heading Northwards) in Gemini in 2013-14 it describes a zig-zag formation. 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 on the map have an apparent magnitude of about +4.8. 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. Other interesting objects on the chart which are observable through telescopes and binoculars are discussed in the main text below. Night sky photographs of the region can be seen below; descriptions of the deep-sky objects (multiple stars, star clusters, nebulae and galaxies) marked on the chart can be found here. |
The Position of Jupiter in the Night Sky, 2011 to 2014 by Martin J Powell
During the first half of 2011, Jupiter was positioned in the constellation of Pisces, the Fishes, with the exception of a 12-day period (late February to early March) in which it crossed the North-western corner of Cetus, the Whale (see the 2009-11 page). In early June 2011 the planet enters Aries, the Ram, where it describes a Southward-facing 'loop' in the South-western corner of that constellation. Whilst moving retrograde (East to West) in early December 2011 Jupiter returns to Pisces, reaching its Western stationary point near the Pisces/Aries border in late December of that year. Jupiter spends 35 days in Pisces then returns to Aries in early January 2012, now moving direct (West to East). As the planet approaches Aries' Eastern boundary in late April 2012 it becomes lost from view in the evening twilight. Jupiter crosses out of sight into Taurus, the Bull, as it passes behind the Sun (as seen from the Earth) in mid-May 2012.
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Jupiter imaged by the joint NASA/ESA/ASI Cassini-Huygens spacecraft in the year 2000, whilst en-route to Saturn. The dark spot at the lower left is the shadow of Jupiter's moon Europa - these shadow transits can be seen through amateur telescopes (Image: NASA) |
When the planet returns to view in the morning twilight
in early June 2012 it is positioned a short distance South of the famous Pleiades
star cluster (Messier
45).
Jupiter's
2012-13 'hybrid' formation (half-loop, half-zigzag) is described North of the
Hyades star
cluster and its leading star, Aldebaran (
Tau or Alpha Tauri). The planet becomes lost from
view in the evening twilight as it passes North of Orion,
the Hunter in late May/early June 2013.
By the time Jupiter
re-appears in the dawn sky around mid-July 2013 it has entered Gemini,
the Twins - the most Northerly constellation of the zodiac (the planet was last
positioned here in 2002). The planet's 2013-14 'zigzag' formation is described
in central Gemini,
South-west of its brightest stars Castor (
Gem or Alpha Geminorum) and Pollux (
Gem or Beta Geminorum). From late 2013 through to mid-2014,
Jupiter appears
as the Southern apex of a continually-changing triangle with Castor
and Pollux. In early July 2014, shortly before Castor, Pollux
and Jupiter
appear to line up, the planet heads into the evening twilight, crossing
into Cancer,
the Crab as it does so.
Jupiter Opposition Data, 2010 to 2015
Jupiter reaches opposition to the Sun (when it is closest to the Earth and brightest in the sky for the year) every 398.9 days on average, i.e. about 33½ days later in each successive year. For the period covered by the above star map, oppositions take place on October 29th 2011, December 3rd 2012 and January 5th 2014. Around opposition, the planet is due South at local midnight in the Northern hemisphere (due North at local midnight in the Southern hemisphere).
The apparent magnitude of the planet at opposition during the period of the star chart is -2.8 (in 2011), -2.7 (in 2012) and -2.6 (in 2014). Jupiter's apparent size (i.e. its angular width as seen from the Earth, measured in arcseconds, where 1 arcsecond = 1/3600 of a degree) at opposition is 49".6 (in 2011) reducing to 48".4 (in 2012) and 46".8 (in 2014).
Because of Jupiter's rapid rotation speed, its disk appears as an oblate spheroid through telescopes and high-magnification binoculars (i.e. it appears flattened at the poles and bulged at the equator). The dimension given above is the apparent equatorial diameter of the planet; its apparent polar diameter is about 6.3% less.
Superior conjunction (when Jupiter passes behind the Sun as seen from the Earth) takes place on May 13th 2012, June 19th 2013 and July 24th 2014. The planet is not visible from Earth for about two weeks on either side of these dates. At superior conjunction the magnitude fades by one whole magnitude to -1.8 (in 2012), -1.7 (in 2013) and -1.6 (in 2014) and the apparent diameter reduces to 32".8 (in 2012), 32".1 (in 2013) and 31".4 (in 2014).
Data relating to Jupiter's oppositions from 2010 to 2015 are provided in the table below.
[Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]
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Apparition Period |
Opposition Circumstances |
Superior Conjunction |
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Opposition Date |
Constellation |
Declination |
Apparent Magnitude |
Diameter (arcsecs) |
Tilt |
View from Earth (North up) |
Distance (AU)* |
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Equatorial |
Polar |
from Earth |
from Sun |
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2010/11 |
2010 Sep 21 |
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Psc |
-2°.1 |
-2.8 |
49".8 |
46".6 |
+2°.3 |
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3.9539 |
4.9576 |
2011 Apr 6 |
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2011/12 |
2011 Oct 29 |
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Ari |
+11°.8 |
-2.8 |
49".6 |
46".4 |
+3°.3 |
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3.9699 |
4.9632 |
2012 May 13 |
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2012/13 |
2012 Dec 3 |
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Tau |
+21°.3 |
-2.7 |
48".4 |
45".3 |
+3°.0 |
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4.0688 |
5.0544 |
2013 Jun 19 |
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2013/14 |
2014 Jan 5 |
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Gem |
+22°.6 |
-2.6 |
46".8 |
43".8 |
+1°.6 |
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4.2104 |
5.1936 |
2014 Jul 24 |
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2014/15 |
2015 Feb 6 |
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Cnc |
+16°.5 |
-2.4 |
45".3 |
42".4 |
-0°.2 |
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4.3462 |
5.3319 |
2015 Aug 26 |
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* 1 AU (Astronomical Unit) = 149,597,870 kms (92,955,807 statute miles) |
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Jupiter opposition data for the period 2010 to 2015 (note that there is no opposition in 2013). The Declination is the angle of the planet to the North (+) or South (-) of the celestial equator; on the star chart, it represents the planet's angular distance above or below the blue line. The angular diameter (or apparent size) of the planet as seen from Earth is given in arcseconds (where 1 arcsecond = 1/3600th of a degree). The Polar Diameter is 6.3% less than the Equatorial Diameter because Jupiter is an oblate spheroid. Jupiter's distance from Earth slowly increases over the period (the planet having passed perihelion in March 2011), causing its angular diameter at opposition to shrink slightly year by year. This is reflected in the planet's apparent magnitude (brightness) which fades slightly over the same period. The Tilt (the inclination of Jupiter's rotational axis relative to the Earth's orbital plane) is positive (+) when Jupiter's Northern hemisphere is tipped towards the Earth and negative (-) when its Southern hemisphere is tipped towards the Earth; the maximum value it can attain is ±3°.4. The Tilt values were obtained from NASA's Jupiter Ephemeris Generator 2.2. All other data was obtained from 'MegaStar', 'Redshift', and 'SkyGazer Ephemeris' software. The Jupiter images were obtained from NASA's Solar System Simulator v4.0. |
Jupiter Conjunctions with other Planets, May 2011 to December 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.
Conjunctions between Jupiter and Venus are perhaps the most spectacular to view and the most photogenic. Between May 2011 and December 2015 there are seven occasions when these two planets can be seen together. For Northern hemisphere observers, the conjunctions of March 15th 2012 and October 26th 2015 are particularly noteworthy, whilst that of July 1st 2015 is noteworthy for Southern hemisphere observers.
The following table lists the conjunctions involving Jupiter which take place at solar elongations of greater than 15°. 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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Jupiter conjunctions with other planets from May 2011 to December 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 Jupiter, e.g. on 2012 Mar 15, Venus is positioned 3°.3 North of Jupiter 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 45°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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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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Jupiter Through The Telescope Jupiter is one of the most rewarding planets to observe through a telescope. Its rapid rotation and ever-changing cloud patterns mean there is always something worthwhile observing or monitoring. The images of the planet seen here were filmed by pointing a video camera through the eyepiece of an 8-inch reflecting telescope in February 2004. The image is inverted (South up) which is the standard orientation of most astronomical telescopes. The rippling effect simulates how the Earth's turbulent atmosphere affects the steadiness and quality of the telescopic image. The diagram below shows the primary features of the planet which one can expect to see through small telescopes. With patience, considerably more detail can be seen depending upon the telescope aperture and the local atmospheric seeing conditions.
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Bright Stars, Nearby Stars and Multiple Star Systems
During the period covered by the star chart, Jupiter is positioned in what is arguably the most interesting region of the entire night sky. Rich in bright stars, asterisms, star clusters and gaseous nebulae, the beginner to astronomy is well advised to become familiar with the constellations surrounding Orion and Taurus since these are ideal signposts to other constellations. Orion itself contains convenient stellar pointers towards the brightest stars in Taurus and Canis Major. A line drawn North-westwards through Orion's Belt leads one to the orange-red star Aldebaran in Taurus, the Bull. Extending the line of the Belt in the opposite direction (South-eastwards) leads one to the brightest star in the night sky, Sirius in Canis Major, the Greater Dog. Finally, a curved line extended North-eastwards from Rigel (at the South-western corner of Orion) through Mintaka (the Western star in the Belt) and Betelgeuse leads one to the star Alhena in South-western Gemini.
The six brightest stars on the star chart are (in order of descending brightness):
Aur or Alpha Aurigae, magnitude
+0.1), a star with a yellow
hue in the constellation of Auriga,
the Charioteer,
CMi or Alpha Canis Minoris, mag.
+0.4), a yellow-white
star in Canis Minor,
the Lesser Dog,
Ori or Alpha Orionis, variable mag.
+0.3 to +0.9), a red
giant
variable
star
with a distinctly orange-red
colour in Orion,
the Hunter,
Tau or Alpha Tauri, mag.
+0.8), another red giant with an orange
tint in Taurus,
the Bull,
Gem or Beta Geminorum, mag.
+1.1), a pale orange-yellow star
in Gemini,
the Twins
and
Gem or Alpha Geminorum, mag.
+1.6), a blue-white
double
star,
also in Gemini.Note
that the brightest star of all - the aforementioned Sirius (
CMa or Alpha Canis Majoris, mag.
-1.4) - is not included in the above listing since, with a declination
of -16°.7, it
is positioned too far South of the celestial
equator to
appear on the chart (the Southern cut-off declination of the chart is about
-7°). Sirius
does however dominate this region of the sky and it cannot be overlooked in
any discussion of the constellations here.
Three of these stars - namely Sirius, Procyon and Betelgeuse - form a near-equilateral triangle in the night sky which is sometimes referred to as The Winter Triangle in the Northern hemisphere because these stars are prominent in Northern hemisphere winter evenings (i.e. summer evenings in the Southern hemisphere). A photograph of these three stars can be seen in the blue box below.
Jupiter is, however, much brighter than all of these stars as it passes through the region between 2011 and 2014. With its steady light and brilliance, the planet is easily distinguished from the surrounding stellar background.
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| Aries, Taurus, Gemini and Orion Photographs showing the region of the night sky through which Jupiter passes from mid-2011 to mid-2014. For the Gemini area chart, stars are visible down to about magnitude +6.5; for the Taurus chart, the limiting magnitude is about +8.0 and for the Aries chart it is about +7.5. Note that the photographs do not have the same scale because of the varying camera lens settings and image resolutions (Move your pointer over the images to identify the constellations and click on the images for their full-size equivalents). |
As it slowly moves along the 'celestial highway' known as the ecliptic (the apparent path along which the Sun, Moon and planets move through zodiac) Jupiter passes numerous bright stars; these are listed below, in chronological order:
2011
Psc or Omicron Piscium,
mag. +4.2) in Pisces,
the Fishes.
Ari or Gamma Arietis,
mag. +4.6) in Aries,
the Ram.
Psc or Alpha Piscis, mag. +3.8)
in Pisces,
the Fishes (moving direct).
Ari or Alpha Arietis, mag.
+2.0) in
Aries,
the Ram (moving direct).
Ari or Alpha Arietis, mag.
+2.0) in
Aries,
the Ram (moving retrograde).
Psc or Alpha Piscis, mag. +3.8)
in Pisces,
the Fishes (moving retrograde).
2012
Psc or Alpha Piscis, mag. +3.8)
in Pisces,
the Fishes (moving direct).
Ari or Alpha Arietis, mag.
+2.0) in
Aries,
the Ram (moving direct).
Cet or Alpha Ceti, mag.
+2.5) in Cetus,
the Whale.
Tau or Alpha Tauri, mag.
+0.8) in Taurus,
the Bull (moving direct).
Tau or Alpha Tauri, mag.
+0.8) in Taurus,
the Bull (moving retrograde).2013
Tau or Alpha Tauri, mag.
+0.8) in Taurus,
the Bull (moving direct).
Gem or Gamma Geminorum, mag.
+1.9) in Gemini,
the Twins.
Gem or Epsilon Geminorum,
mag. +3.0) in Gemini,
the Twins.
Gem or Zeta Geminorum,
mag. +3.9v) in Gemini,
the Twins (moving direct).
Gem
or Delta Geminorum,
mag. +3.5) in Gemini,
the Twins (moving direct). Gem
or Delta Geminorum,
mag. +3.5) in Gemini,
the Twins (moving retrograde).2014
Gem or Zeta Geminorum,
mag. +3.9v) in Gemini,
the Twins (moving retrograde).Gem or Zeta Geminorum,
mag. +3.9v) in Gemini,
the Twins (moving direct). Gem
or Delta Geminorum,
mag. +3.5) in Gemini,
the Twins (moving direct).
Gem or Alpha Geminorum,
mag. +1.6) in Gemini,
the Twins.In the introduction it was mentioned that Jupiter, Castor and Pollux form a variety of triangle shapes in the night sky from around late 2013 to around mid-2014. Observers with a geometrical leaning may be interested to know the dates on which the three celestial bodies form right-angled and isosceles triangles. The first right-angled triangle is formed on August 4th 2013 (with Castor at the perpendicular angle) when Jupiter is moving direct and is visible in the morning sky. The distance between Castor and Jupiter on this occasion (i.e. the length of the adjacent side of the triangle) is 16°.2. On August 22nd 2013 they form an isosceles triangle, with Jupiter at the Southern apex, the long sides of the triangle measuring 13°. Three weeks later (September 12th) a second right-angled triangle is formed, this time with Pollux at the perpendicular angle, 10°.1 North-east of Jupiter. On January 2nd 2014, just three days before Jupiter's opposition, the three again form a right-angled triangle with Pollux at the perpendicular angle, 9°.9 North-east of Jupiter. After entering the evening sky, with the planet still retrograding, a second isosceles triangle is formed between the three on January 29th 2014, the long sides on this occasion measuring 12°.7. The last isosceles triangle is formed on April 11th 2014, the long sides measuring 12°.6, Jupiter now having returned to direct motion. The finale of this trigonometrical menagerie takes place on May 9th 2014 with a right-angled triangle, Pollux again being at the perpendicular angle, 9°.5 distant from Jupiter.
Deep-Sky Objects
Details of other interesting objects in the region (star clusters, variable stars, nebulae, galaxies, etc) can be found on the Zodiacal Sky: Aries-Taurus-Gemini page.
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Jupiter Transit Altitudes, 2010 to 2015
Jupiter is the largest of the Solar System planets and it can show considerable detail even through modest-sized telescopes. A major factor determining the likelihood of seeing a clear telescopic image is the altitude (angle above the horizon) of a planet at the time of observation. For the naked-eye observer, apart from the increased likelihood of obstruction from trees and buildings, a planet's low altitude is generally of little c
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Jupiter took on an unusual appearance when seen through telescopes during 2010 after its Southern Equatorial Belt (SEB) faded from view. Fadings of the SEB occur at irregular intervals, the last occasion having been in the early 1990s. As Jupiter became lost from view in March 2011 the SEB was beginning to return. |
onsequence, however for the telescopic observer high altitude is essential in order to minimise the effects of turbulence, atmospheric dimming and light pollution (skyglow) which prevails near the horizon. Consequently, telescopic observers consider high altitude transits (when a celestial body crosses the observer's meridian, reaching its highest point in the sky) as more favourable than low altitude transits. As a general rule, telescopic observation is best done when a celestial body's altitude is greater than about 30°; hence observation in the couple of hours after rising or before setting is best avoided, unless there is no other alternative.
Jupiter's meridian transit altitude (as seen from any given point on Earth) varies from one year to the next in the course of its 11.8-year journey through the zodiac constellations. Its most Northerly point is attained in Gemini (around 23½° North of the celestial equator) then - some six years later - its most Southerly point is attained in Sagittarius (around 23½° South of the celestial equator). In the intervening years, the planet lies somewhere between these two extremes.
The meridian transit altitude at which an observer sees a planet depends not only upon the constellation in which the planet is positioned at the time, but also upon the observer's latitude. As a result, certain apparitions are more favourable to observers in one hemisphere than to observers in the opposite hemisphere.
In the 2007-8 period, observers at mid-Northern latitudes saw Jupiter at its lowest meridian transit altitude for some twelve years, as the planet traversed the Southernmost constellations of the zodiac. Observing circumstances for Northern hemisphere observers have gradually improved since 2009, when the planet began to ascend the ecliptic once more, moving North-eastwards through Capricornus, Aquarius and Pisces (Jupiter crossed the celestial equator in February 2011).
Conversely, during 2007-8, observers in mid-Southern latitudes saw Jupiter high up in the sky when it reached meridian transit (due North in the Southern hemisphere) providing optimal viewing conditions for telescopic observers. Over the next number of years, as the planet passes through the most Northerly constellations of the zodiac, observers at mid-Southern latitudes will see the transit altitude reduce quite considerably.
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Transit altitudes of Jupiter at successive oppositions from 2010 to 2015, as seen from a variety of latitudes. The Declination (Dec.) is the angle of the planet to the North (+) or South (-) of the celestial equator at the time of the planet's opposition. The Altitude Range is the approximate altitude variation over the course of the apparition, e.g. for the 2012/13 apparition at latitude 40° North, the transit altitude of Jupiter ranges from (71°.3 - 2°.0) = 69°.3 to (71°.3 + 2°.0) = 73°.3. The table demonstrates that, from 2010 through to 2014, Jovian transit altitudes improve for Northern hemisphere observers but worsen somewhat for Southern hemisphere observers. |
What are the best and worst case scenarios regarding Jupiter's transiting altitude? Northern hemisphere observers witnessed their worst case scenario (and Southern hemisphere observers witnessed their best) in the 2007-8 observing season, when Jupiter passed through the Southernmost zodiac constellations (see table on the 2009-11 page). Jupiter will reach its most Northerly point along the ecliptic in the 2013/14 apparition, when it is positioned in Gemini. Observers at mid-Northern latitudes will then see the planet transit at around 60° to 70° high in the sky (best case scenario); mid-Southern hemisphere observers will fare rather worse, the planet transiting at only 20° to 30° high (worst case scenario).
Moon near Jupiter Dates, 2012
The Moon is easy to find, and on one or two days in each month, it passes Jupiter in the sky. Use the following table to see on which dates the Moon is in the vicinity of the planet:
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Moon near Jupiter dates for 2012 (no entry is given for May because in this month, Jupiter is too close to the Sun - and therefore not visible - when the Moon is nearby). The Date Range shows the range of dates worldwide (allowing for Time Zone differences across East and West hemispheres). Note that the dates, times and separations at conjunction (i.e. when the two bodies are at the same Right Ascension) are measured from the Earth's centre (geocentric) and not from the Earth's surface (times are Universal Time [UT], equivalent to GMT). The Sep. & Dir. column gives the angular distance (separation) and direction of the planet relative to the Moon, e.g. on March 25th at 23:58 UT, Jupiter is 3°.1 South of the Moon's centre. The Moon Phase shows whether the Moon was waxing (between New Moon and Full Moon), waning (between Full Moon and New Moon), at crescent phase (less than half of the lunar disk illuminated) or gibbous phase (more than half but less than fully illuminated). |
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The Moon moves relatively quickly against the background stars (in an Eastward direction, at about its own angular width [0º.5] each hour, or about 12º.2 per day) and because it is relatively close to the Earth, an effect called parallax causes it to appear in a slightly different position (against the background stars) when seen from any two locations on the globe at any given instant; the further apart the locations, the greater the Moon's apparent displacement against the background stars. Therefore, for any given date and time listed in the table, the Moon will appear closer to Jupiter when seen from some locations than from others. For this reason, the dates shown in the table should be used only for general guidance.
Position of Jupiter's Four Brightest Moons
Jupiter's four brightest moons (satellites) - namely Ganymede (magnitude +4.6 at opposition), Io (+5.0), Europa (+5.3) and Callisto (+5.6) - can readily be seen through telescopes or steadily-held binoculars. The moons are seen to change their position in relation to each other, along the planet's equatorial plane, from one night to the next. In fact, their motion can be detected in the space of just a few hours.
Because of their low magnification, binoculars may have some difficulty detecting Io since it is the closest of the four moons to the planet; it never lies more than three Jupiter-diameters away. Europa is easier, but Ganymede is the easiest of the four to see. Callisto moves furthest away from the planet but it is also the faintest of the four.
Due to Jupiter's shallow axial tilt (3º.1 to the plane of its orbit), the Jovian moons appear to present a more-or-less linear motion when seen from the Earth (this is in contrast to, say, Saturn with its relatively high axial tilt (26º.7 ), which causes its moons to mostly follow apparent elliptical paths around the planet when viewed from the Earth - see Saturn's moon positions). Approximately every six years, when the Earth passes through Jupiter's equatorial plane, the Jovian moons are seen to become involved in mutual occultations (where the moons pass in front of each other) and mutual eclipses (where a moon's shadow falls upon another moon). Numerous mutual events took place in 2009 and they continued (to a lesser extent) into 2010.
The following Flash program shows the current position of Jupiter's four brightest moons (based on your computer's clock and Time Zone settings):
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The Positions of Jupiter's four brightest satellites in relation to the planet (the graphic requires the Adobe Flash Player plug-in to display correctly). Binocular and terrestrial telescope users in the Northern hemisphere should use the default 'Erect Image' (North up, East to the left) setting; Southern hemisphere observers using this equipment will need to click on the 'Inverted' (North down, West to the left) button. Users of astronomical telescopes in the Northern hemisphere will need to use the 'Inverted' option to match the view in their telescope, whilst those in the Southern hemisphere should use the default ('Erect Image') setting. The 'Mirror Reversed' button applies to astronomical telescopes with a star diagonal attached. Enter the required values for Date (in the form mm/dd/yyyy) and Time and click on 'Recalculate' to see the position of the moons for any date and time between January 1st 1900 AD and December 31, 2100 AD. The Timezone offset from UT is determined by the settings in your web browser. Other details shown are the planet's apparent magnitude, its angular size (in arcseconds), its distance from the Sun (in Astronomical Units) and the planet's System II Longitude (the Jovian longitude of the central meridian, i.e. the imaginary line through the centre of the planet's disk from pole to pole). Since Jupiter's outer layers are gaseous, the planet does not rotate as a solid body; in fact the equatorial region (known as System I ) makes one rotation in 9h 50m 30s whilst the rest of the planet (System II) rotates once in 9h 55m 40s. The Great Red Spot is located in System II, at a latitude of about 22° South. Pressing the 'Display' button generates a list of Jovian satellite phenomena for the selected date - namely transits (when a moon or its shadow passes across the planet's disk), occultations (when a moon passes behind the planet's disk) and eclipses (when a moon enters Jupiter's shadow). All of these events can be observed in telescopes. The next three transit times of the Great Red Spot (GRS) - i.e. when it crosses the planet's central meridian - are also listed, the GRS itself being displayed on the graphic. Note that the accuracy of these times is dependant upon the Jovian longitude of the GRS, which slowly drifts over time. By default, the program uses a longitude of 98°, however this is now incorrect and the value must be updated in order to provide accurate transit times. As of late 2011, the longitude of the GRS was approximately 173°, so this value should be entered in the 'GRS Longitude' box and the timings recalculated by pressing the 'Display' button. The current longitude of the GRS will normally be given on Sky & Telescope's Great Red Spot page, where a list of transit times for the current year is also provided. Times of all events in the program are given in Universal Time (UT) which is equivalent to Greenwich Mean Time (GMT). The 'Jupiter's Moons' program by John Bartucci is available as a standalone, executable (exe) file which can be downloaded from the The Wilderness Center Astronomy Club website. |
Finding Jupiter in Your Local Night Sky
Where in the night sky should I look for Jupiter 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. South-east, East-South-east) and an angle to look above the horizon (known as altitude or elevation).
From late July 2013, when Jupiter is moving through Gemini, The Big Dipper (also known as The Plough) can be used to locate Jupiter using the method shown in the animation here. Prior to this date, use the following Javascript program to help find the planet in your night sky throughout 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 Jupiter, refer to the 'Finding The Planets ..' 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 Jupiter 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 the elongation (its angular distance from the Sun as seen from the Earth) is less than about 15°, the planet 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 15°, making observation difficult or even impossible. This particularly applies throughout the local summer months at higher latitudes. To locate Jupiter, 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 Jupiter 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 two diagrams below). If Jupiter's altitude is less than about 10° it might be difficult 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
Jupiter 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 Jupiter rises in daylight (i.e. if the Sun is already above the horizon), you will have to wait until dusk to see it - in which case, 'fast forward' to a time shortly after sunset, then note down the time and direction. The same method can also be used to find any of the visible constellations in your night sky.
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The Current Night Sky over
Windhoek,
Namibia
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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. |
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Star Charts showing Positions of the Planets:
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Venus, 2011-2012 |
Mars, 2011-2012 |
Saturn, 2006-2013 |
Uranus, 2006-2018 |
Neptune, 2006-2023 |
Pluto, 2006-2022 |
Current Position of the Sun and the Brighter Naked-Eye Planets ('Live' Star Map)
Credits
.Copyright © Martin J Powell, June 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 (
