|
|
The Position of Jupiter in the Night Sky:
2009 to 2011
by Martin J. Powell
The path of Jupiter against the background stars of Capricornus, Aquarius and Pisces from January 2009 to May 2011, with positions marked at the start of each month (click on the thumbnail for the full-size image, 112 KB). Periods when the planet was unobservable (i.e. when it was too close to the Sun, or passed behind it) are indicated by a dashed line; hence the planet became lost from view (in the evening sky) in early January 2009 and became visible again (in the morning sky) in mid-February 2009.
The chart shows the changing shape of a planet's apparent looping formation as it moves through the zodiac. After crossing the ecliptic (heading Southwards) in 2008, when Jupiter described a zig-zag formation in Sagittarius, Jupiter described a hybrid formation (half loop, half zig-zag) in 2009, followed by a conventional, Southward-facing loop in 2010.
The star map applies to observers in the Northern hemisphere (i.e. North is up); for the Southern hemisphere view, click here (117 KB; the Southern hemisphere chart applies to observers situated south of the Tropic of Capricorn [23½° South]). The Milky Way is shown in dark grey; the faintest stars on the map have an apparent magnitude of about +4.8. Printer-friendly versions of this chart are available for Northern (51 KB) and Southern hemisphere (53 KB) 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.
Throughout 2008, Jupiter was seen in the constellation of Sagittarius, the Archer, where it had been situated since late 2007 (for details, see the 2006-8 page). The planet entered Capricornus, the Sea Goat, in early January 2009; its entire 'hybrid' loop formation was described within Capricornus, close to the constellation's Eastern border. Jupiter then proceeded Eastwards (direct motion) and entered Aquarius, the Water Carrier, in early 2010; it passed behind the Sun during its passage through this constellation and was not visible for much of its time there.
By the time Jupiter emerged in the dawn sky in late March 2010, it was fast approaching the border with Pisces, the Fishes, which it entered in early May of that year. The planet's Southward-facing loop was mostly described within this constellation, making a brief return to Aquarius from mid-October to mid-December 2010, during which time it reached its Western stationary point. In early February 2011 the planet resumed Eastward motion, re-entered Pisces and crossed the celestial equator, heading Northwards. Jupiter briefly 'escaped' the zodiac, heading into the non-zodiac constellation of Cetus (pronounced 'SEE-tus'), the Whale, for a 12-day period from late February into early March 2011, before it re-entered Pisces once more.
Jupiter
in Virgo, 2005 (click on the thumbnail for the full-size image, 132 KB). Jupiter
(then magnitude -2.0)
greatly outshone Spica, the brightest star in Virgo (magnitude +1.2) which
is seen at
the bottom left of the picture. An annotated version
of the photograph can be seen here
(12 KB).
For the period covered by the above star map, Jupiter oppositions took place on August 14th 2009 and September 21st 2010. Around opposition, the planet is due South at local midnight in the Northern hemisphere (due North at local midnight in the Southern hemisphere).
Jupiter's 2010 opposition was interesting for two very different reasons. Firstly, it was the planet's brightest and best opposition of its entire 11.8-year orbit, the planet reaching perihelion (its closest point to the Sun, at 4.95 Astronomical Units or 740 million kms) just six months later, in March 2011. Secondly, opposition took place on the same day as that of Uranus, the opposition times of the two planets being just five hours apart (see section Triple Conjunctions below).
Superior conjunction (when Jupiter passed behind the Sun as seen from the Earth) took place on January 24th 2009, February 28th 2010 and April 6th 2011. The planet was not visible from Earth for about two weeks on either side of these dates.
The path of Jupiter from Dec 2005 to May 2011 (click on the thumbnail for the full-size image, 196 KB). Showing Jupiter's journey through seven constellations over the course of 5½ Earth years (nearly half a Jovian orbit). Positions are marked on the 1st of each month; dashed lines indicate periods of invisibility from the Earth. A printer-friendly (greyscale) version of the chart is available here (94 KB).
The apparent magnitude of the planet during the period of the star chart was -2.8 (at opposition in 2009) and -2.9 (at opposition in 2010). At superior conjunction, the magnitude fell to -1.9 (in 2009), -2.0 (in 2010) and -2.1 (in 2011).
The apparent size of the planet (i.e. its angular size as seen from the Earth, measured in arcseconds, where 1 arcsecond = 1/3600 of a degree) at opposition was 48".9 (in 2009) increasing to its largest theoretical diameter of 49".9 (in 2010).
The dimension given above is the apparent equatorial diameter of the planet; its apparent polar diameter is about 6.3% less.
[Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]
Triple Conjunctions
During the 2009-2011 period, Jupiter was involved in two triple conjunctions with planets (i.e. three close passes of the same two planets within a single apparition); the first was with Neptune in 2009 (near the Capricornus/Aquarius border) and the second with Uranus in 2010-11 (in Pisces). For those who had not yet glimpsed these faint outer gas giants, the 2009-11 period offered good opportunities to find them with binoculars via a short 'star hop' from Jupiter. Details of the Jupiter-Neptune triple conjunction (with a finder chart) can be found here; details of the Jupiter-Uranus triple conjunction (with an animation and a finder chart) can be found here.
Bright Stars, Nearby Stars
and Deep-Sky Objects
Throughout
the period of the star chart, Jupiter was considerably brighter than any of the stars shown.
The brightest stars on the chart are all situated in non-zodiac constellations.
The brightest star
shown is Fomalhaut (
PsA or Alpha Piscis Austrini, magnitude
+1.2) in Piscis Austrinus (or Piscis Australis) - the Southern
Fish, the only constellation in the night sky which has two official names in use. Fomalhaut is
a blue-white star, 22 light years
distant, whose name derives from the Arabic for 'the fish's mouth';
on older star charts, it is the destination of the stream of water which
is poured by Aquarius. With its Southerly declination (angle relative
to the celestial equator) of -30°, Fomalhaut is
difficult to view from latitudes North of about 55° North and is not visible
at all North of 60° North. Observers at these higher latitudes can only see
it during the
late summer and early autumn months, for
a couple of hours each night, low down near the Southern horizon.
Also occupying this rather
visually barren region of the night sky, to the North-east of Fomalhaut, is
Deneb Kaitos or
Diphda (
Cet or Beta Ceti, magnitude +2.0), the brightest star of the constellation
Cetus, the Whale. Its name is Arabic
for 'the Southern branch of the tail', i.e. the tail-end of the Whale.
The
stars Markab (
Peg or Alpha Pegasi, mag.
+2.5) and Algenib
(
Peg or Gamma Pegasi, mag. +2.8v) in Pegasus (the
Winged Horse) form the Southern corners of the Great
Square of Pegasus
- four medium-bright stars of a near-perfect square just to the North of the Circlet
of Pisces.
The other stars of the Great
Square are
Sirrah
(
Peg or Delta Pegasi, mag. +2.0) and Scheat (
Peg or Beta Pegasi, mag. +2.4v). Sirrah is also
confusingly referred to by the name Alpheratz (
And or Alpha Andromedae) since it is technically situated across
the border in Andromeda.
The
brightest zodiac constellation star on the chart is Deneb Algiedi or
Deneb Algedi (
Cap or Delta Capricorni,
mag. +2.9v) in the tail of Capricornus.
Jupiter
described its 2009 loop just to the North of this star, passing 1°.7
from it (while retrograding)
on July 29th of that year, and 1°.8 from
it on December 20th (moving direct). At opposition on August 14th 2009,
Jupiter,
Deneb Algiedi and Nashira (
Cap or Gamma Capricorni, mag. +3.6) formed a small, near-equilateral triangle at the tail of the Sea Goat.
Just
over
4° to the West
of Deneb Algiedi is the fainter star 
Cap
(Iota Capricorni, mag. +4.2). Jupiter was in the vicinity of this star from late September of 2009, through October (when
it reached its Western stationary point and then resumed direct motion) and
into early November. The planet passed
18' (0°.3) to
the North of Cap on
September 24th 2009 and 22' (0°.3)
to the North of it on November 1st 2009; both of these events were visible in
the evening sky and were easily contained within the field
of view of
telescopes fitted with low-magnification eyepieces.
Capricornus, Aquarius and Piscis Austrinus A photograph showing the region of the night sky which Jupiter passed through during the 2009-11 observing seasons (click on the thumbnail for the full-size picture, 331 KB). The region of the 2009-11 star chart which is visible in the photograph is contained within the red trapezium here (39 KB) and an annotated version of the photograph can be seen here (91 KB). The picture was taken from latitude 51½° North in the early morning hours of mid-August 2005. Piscis Austrinus is seen shortly after meridian transit (low in the South), Aquarius is in the South-South-west and Capricornus is in the South-west. Stars in the upper region of the photo are visible down to about magnitude +8.0; fewer faint stars are visible near the horizon because of the dimming effects of haze and atmospheric extinction.
Also contained within the star chart are a few deep-sky objects (objects beyond our Solar System) which are worthy of mention since they can be seen through binoculars and small telescopes.
Aquarius contains two of the most interesting planetary nebulae in the night sky. The term is a misleading one since they are neither planets nor nebulae! In fact, a planetary nebula is a dying star whose shells of ejected material are heated and illuminated by the ultraviolet radiation of the star itself. The stars are typically in the red giant phase of their life, which later contract into white dwarfs. Because of the various forms in which the ejected material takes - and the varying angles at which they are presented to the Earth's line-of-sight - planetary nebulae provide us with some of the most spectacular sights in the night sky, though larger telescopes are required to fully appreciate their structural details.
Planetary nebulae were so-named by the English (but German-born) musician and astronomer William Herschel in the late 18th century; his term described the objects' telescopic appearance, though of course their true physical nature was unknown at the time.
The
first noted
planetary nebula of interest in Aquarius
can be found within the region of dim stars to the South-west
of the star Skat ( Aquarii, mag. +3.3).
The Helix Nebula (NGC
7293, mag.
+7.3) is the nearest and brightest planetary to the Earth, being at an
estimated distance of 300 light
years (where 1 light
year = 63,240 AU).
It is visible in binoculars as a pale, rounded glow when seen under
dark skies; it has been described as resembling a 'smoke-ring'. Since it is
so close, it appears as one of the largest planetaries in the sky, covering
an area about 0°.25 across, or about half the apparent size of the Full
Moon. Telescopes fitted with low-power (wide field) eyepieces show a circular
misty patch, with some structural detail visible within the nebulosity; it appears
grey, sadly lacking the brilliant coloration often seen in observatory photographs.
The use of a nebula
filter (which
blocks out light
pollution but allows the emission wavelengths of nebulae to pass through) helps to increase the contrast of the nebula against the background
sky, subsequently making it easier to see.
The second (rather less spectacular) planetary within the Aquarian boundary lies about 1°.3 West of the star v Aquarii (Nu Aquarii or 13 Aqr, mag. +4.5). Through binoculars, the Saturn Nebula (NGC 7009, mag. +8.0) appears as little more than a faint spot of light, at the limit of visibility. Small telescopes show it to be non-stellar in appearance, elliptical in shape with a greenish hue. Large telescopes reveal two faint extensions (called ansae) on opposite sides of the planetary, giving it a passing resemblance to the famous ringed planet after which it is named. This planetary is thought to be around 2,500 light years away; the central star which is responsible for the surrounding nebula is magnitude +12.8 and even through large telescopes is difficult to see.
About
five degrees North of Aquarius' brightest star Sadalsuud ( Aquarii, mag. +2.9)
and eight degrees West
of Sadalmelik ( Aquarii, mag. +3.0) is the globular
cluster Messier
2
(M2 or
NGC 7089, mag. +6.4). Globular
clusters are dense concentrations of stars, all of which are about
the same age and chemical composition. The number of stars in a globular cluster
can lie anywhere between 10,000 and several million (!) and they are
amongst the oldest objects in the universe, being perhaps 10 billion years old.
M2
appears as a large, bright glow in binoculars and some may even be able to spot
it faintly with the naked-eye under truly dark skies. Telescopes show a pretty
concentration of stars of around 13th magnitude and fainter; individual stars
can be difficult to resolve in the stellar haze. The globular has an apparent
diameter of 13' (13 arcminutes, where 1 arcminute = 1/60th of a degree)
and it lies about 50,000 light years distant, in the outer halo of
the Milky Way galaxy.
|
|
Deep-Sky Objects in Aquarius, imaged by the Hubble Space Telescope (click on a thumbnail for a larger picture, 7 KB / 9 KB / 26 KB) Three examples of deep-sky objects which can be glimpsed in binoculars and small telescopes: (Left) the Helix Nebula (NGC 7293), (Centre) the Saturn Nebula (NGC 7009) and (Right) the globular cluster M2 (NGC 7089) (Images by NASA/ESA). The beautiful colours so evident in the planetary nebulae unfortunately cannot be seen through telescopes because they are too faint to be detected by the naked-eye - a situation which has been likened to viewing flowers in the night-time. Long-exposure photographs taken with digital/CCD cameras attached to telescopes will however reveal some of the coloration. A highly detailed, zoomable image of the Helix Nebula can be seen at the HST's European site and a short video showing its likely morphology can be seen on YouTube.
The difficulty in viewing nebulae, globular clusters and galaxies through binoculars and small telescopes demonstrates an important point regarding the quoted apparent magnitudes of such deep sky objects. The apparent magnitude of the Helix Nebula, for example, is normally listed in astronomical catalogues at around +7.0 - potentially within easy reach of most binoculars - however this is a somewhat misleading figure because it refers to the magnitude the planetary nebula would have if it were a single point of light (i.e. like a star). In reality a planetary nebula is an extended object (the Helix Nebula measures about 12' by 10'). As well as the apparent magnitude, some authors, when giving brightness values for objects such as galaxies, nebulae and planetary nebulae, also include the object's surface brightness, i.e. its apparent magnitude allowing for the fact that it is spread over an area of the sky (this is usually the magnitude per square arcminute). The surface brightness of the Helix Nebula works out at about magnitude +13 (almost as faint as Pluto!) which more accurately reflects its faintness in the sky - and explains why it is such a difficult object to see. Consequently, observers should not be disappointed if they fail to spot it.
Jupiter Transit Altitudes, 2005 to 2010
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 gradually improved from 2009, when Jupiter began to ascend the ecliptic, moving North-eastwards through Capricornus, Aquarius and Pisces.
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. Although the period from 2009-10 saw the transit altitude reduce from these latitudes, it remained sufficiently high (mostly above 50°) so as not to adversely affect telescopic observations.
Transit altitudes of Jupiter at successive oppositions from 2005 to 2011, as seen from a variety of latitudes (click on the thumbnail for the full-size table, 34 KB). 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 2005/6 apparition at latitude 40° North, the transit altitude of Jupiter ranged from (35°.3 - 3°.3) = 32° to (35°.3 + 3°.3) = 38°.6. Note that, from 2009, Jovian transit altitudes improved for Northern hemisphere observers but worsened slightly for Southern hemisphere observers.
For a more detailed assessment of Jupiter's varying transit altitudes and their significance for telescopic observers, see the current Jupiter page.
Credits
Copyright Martin J Powell July 2009
Site hosted by TSOHost |
