The Mars Apparition of 2011-2012 by Martin J Powell

Following superior conjunction on February 4th 2011 (when it passed directly behind the Sun) Mars passed through the perihelion point in its orbit (i.e. its closest point to the Sun) on March 9th. The planet was then positioned 1.3814 Astronomical Units (206.6 million kms or 128.4 million miles) from the Sun and 2.3606 AU (353.1 million kms / 219.4 million miles) from the Earth. Its first appearance in the dawn sky (rising in the East before sunrise) took place from around early May, visible from Equatorial and Southern hemisphere latitudes. From mid-Northern latitudes its appearance began around late May. At high Northern latitudes, the long summer twilight delayed Mars' appearance until around mid-July, by which time the planet was rising some three hours before the Sun.

Two months into the apparition, Mars appears as a feeble, pale-orange star of apparent magnitude +1.3, barely gaining any significant altitude (angle above the horizon) before disappearing into the brightening twilight. Telescopically Mars is a disappointing sight at this time, its low altitude and tiny apparent size frustrating most attempts to obtain a steady and clear view of the planet's surface. Around mid-July the Martian disk appears just 4.2 arcseconds across (where 1 arcsecond = 1/3600th of a degree) with a gibbous phase of about 96% illumination. By late July 2011, the Northern hemisphere summer twilight recedes sufficiently for Mars to become clearly visible to observers at high Northern latitudes, rising in the North-eastern sky about 3½ hours before sunrise. By mid-August 2011, the planet rises in darkness from all but the Polar regions of the world.

After emerging in the dawn sky, Mars moves steadily Eastwards (direct motion) through the following constellations, its brightness varying with its changing distance and aspect as seen from the Earth:

On August 31st 2011, Mars passes 0º.9 North of the star Wasat ( Gem or Delta Geminorum, magnitude +3.5) in the constellation of Gemini, the Twins. Three days later it passes 9º.1 South of Castor ( Gem or Alpha Geminorum, mag. +1.6), Gemini's second-brightest star and then 5º.8 South of Gemini's brightest star Pollux ( Gem or Beta Geminorum, mag. +1.1) on September 9th.

On September 15th the Red Planet enters Cancer, the Crab, the zodiac's faintest constellation. Located at its centre is a well-known open cluster called Praesepe (pronounced 'pree-SEE-pee') or alternatively, The Beehive Cluster (designated Messier 44 or NGC 2632). This large star cluster can be glimpsed with the naked-eye from dark locations as a hazy patch of light; through binoculars it is an easy and pretty sight. Mars crosses the Praesepe star cluster between October 1st and 2nd, passing a little to the South of its centre (see the photograph below).

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The following day (October 3rd) Mars passes 1º.1 North of the star Asellus Australis ( Cnc or Delta Cancri, mag. +3.9) and six days later, 6º.5 North of Acubens ( Cnc or Alpha Cancri, mag. +4.5). On October 19th the planet moves from Cancer into Leo, the Lion, where it is to spend the brighter part of the 2011-12 apparition.

Three weeks after entering Leo - on November 10th 2011 - Mars passes 1º.4 North of that constellation's brightest star Regulus ( Leonis or Alpha Leonis, mag. +1.3 - for more details, see below). On December 2nd, Mars reaches western quadrature (90º West of the Sun). When seen from the Earth, the planet then shows its minimum phase (the percentage of the planet's disk which is illuminated - in this case, 89%) making it appear distinctly gibbous when seen through telescopes.

On December 25th 2011 (Christmas Day) Mars passes 1º.2 North of the fourth-magnitude star  Leonis (Sigma Leonis) at the foot of the Lion's hind leg. Now positioned well into the Southern section of its 2011-12 loop, Mars' daily apparent motion through the night sky slows as the Earth begins to 'catch up' with the planet in its slower and more distant orbit around the Sun.

With the arrival of 2012 Mars begins to brighten significantly as the distance between the Earth and the Red Planet continues to reduce. Now shining at magnitude -0.1, Mars appears distinctly orange and non-stellar to the naked-eye, outshining all the stars in this region of the night sky. As the planet heads into the constellation of Virgo, the Virgin for a three-week period beginning on January 14th, it is brightening day by day. Through telescopes, the Martian disk now has an apparent diameter of about 10" (10 arcseconds), revealing considerable surface detail.

On January 25th 2012, mid-way through its vacation in Virgo, Mars reaches its Eastern stationary point, 8º.7 SSW of  the Lion's tail-star Denebola ( Leo or Beta Leonis, mag. +2.1) and 1º.6 WSW of the fourth-magnitude variable star Virginis (Nu Virginis, located just across the border in Virgo). Now moving retrograde (i.e. moving from East to West against the stellar background), Mars returns to Leo on February 3rd.

Mars reaches aphelion (the most distant point in its orbit from the Sun) on February 15th 2012, when it is 1.6659 AU (249.2 million kms / 154.8 million miles) from the Sun and 0.7129 AU (106.6 million kms / 66.2 million miles) from the Earth. For the Earthbound observer, Mars' aphelion passage at this crucial stage of the apparition is very significant, since it explains why the 2011-12 apparition is the worst for 17 years.

Accelerating into the retrograde stage of its loop, Mars passes 2º South of the fourth-magnitude double star  Leonis (Iota Leonis - of which, see below) - on February 19th 2012 and two days later, 2º.7 North of  Leonis.

Mars reaches opposition (when it is directly opposite the Sun in the sky and brightest for this apparition) on the night of March 3rd 2012, positioned 5º.4 SSW of the star Coxa ( Leo or Theta Leonis, mag. +3.9) and 4º.5 West of   Leonis. This is not, however, Mars' closest point to the Earth during this apparition; because of the eccentricity of its orbit, Mars' perigee (its closest point to Earth) takes place two days later - on March 5th - when it is 0.6737 AU (100.7 million kms / 62.6 million miles) from the Earth.

At opposition, a superior planet rises around sunset, is visible throughout the night and sets around sunrise. Its highest point in the sky is reached when it crosses the observer's meridian at local midnight (due South at midnight in the Northern hemisphere and due North at midnight in the Southern hemisphere). A list of meridian transit altitudes and directions of the planet at opposition for various latitudes over several Martian oppositions is given in the table below.

On opposition day in 2012, Mars shines at magnitude -1.2 and has an apparent disk diameter of 13".9. This is not as bright nor as large (when seen through a telescope) as it was at its previous opposition in January 2010, when the planet reached magnitude -1.3 and had an apparent diameter of 14".1. Indeed, its opposition disk size and brightness in 2012 has not been so poor since the opposition of February 1995. Such distant and dim oppositions, taking place when the planet is near the aphelion position in its orbit, are often referred to as aphelic oppositions (for more details, see below).

Having passed opposition, Mars enters the evening sky (rising before sunset) and begins to fade as its distance from Earth increases once more. The planet reaches its Western stationary point, some 4º.3 ENE of Regulus, on April 16th, after which it resumes direct motion (West to East) against the background stars. In early May 2012, with the advancing Northern hemisphere summer twilight, observers positioned North of about 60º North latitude effectively lose their view of Mars as the evening sky becomes too light for the planet to be seen.

By the time Mars reaches eastern quadrature (90º East of the Sun) on June 8th the planet has faded considerably to magnitude +0.5, its apparent diameter having fallen below 8" and its phase having shrunk from 100% (at opposition) to 89%. Three days later (June 11th) Mars passes 0º.9 South of  Leonis and continues to head towards Leo's South-eastern boundary.

Mars enters Virgo on June 21st 2012 as it proceeds South-eastwards, a little to the North of the ecliptic (the apparent path along which the Sun, Moon and planets move). Its Eastern elongation from the Sun slowly narrowing, Mars passes close to several bright stars (and one planet) in Virgo over the following two months.

On June 28th Mars passes 0º.2 South of the star Zavijah or Zavijava ( Vir or Beta Virginis, mag. +3.6). For several hours centred around 10:00 UT, the narrow separation of the two celestial bodies makes them resemble an easy naked-eye double star, Mars being the brighter of the pair and of course, coloured pale orange. Zavijah is technically a yellow star although this is difficult to detect through binoculars and telescopes.

With Mars' solar elongation reducing to 70º by mid-July, observers in higher Northern hemisphere latitudes begin to have some difficulty viewing the planet after sunset as it begins to languish low down in the summer dusk sky. From these latitudes, the lengthy twilight and the shallow angle of the ecliptic to the Western horizon after sunset combine to worst effect, positioning the planet low down in the West at dusk, thus making it difficult to view.

On July 13th 2012 Mars passes 1º.3 South of the star Zaniah ( Vir or Eta Virginis, mag. +3.9) and eleven days later (July 24th) 3º South of the interesting double star named Porrima or Arich ( Vir or Gamma Virginis, mag. +2.8 - see below for more details). In late July 2012 Mars moves to the South of the ecliptic, then on August 6th it passes 2º South of another double star  Vir (Theta Virginis, mag. +4.4 - more below). Finally, the Red Planet encounters Virgo's brightest star Spica ( Vir or Alpha Virginis, mag. +1.0), passing 1º.9 to the North of it on August 13th.

On August 17th 2012, Mars passes 2º.9 South of the ringed planet Saturn, in what astronomers term a planetary conjunction (for details of this and other planetary conjunctions involving Mars this apparition, see below). At magnitude +0.9, Saturn is well past its brightest at this time, having faded since reaching opposition in April 2012 (see the Saturn page for more details). Although this is potentially Mars' best planetary conjunction of 2011-12, it is only visible with ease from latitudes South of about 45º North.

As August 2012 draws to a close, Mars exits the star chart coverage, entering the constellation of Libra, the Balance (or Scales) on September 5th. As it proceeds through the Southern constellations of the zodiac, Mars' distance from Earth increases, causing its apparent size to shrink. Its phase, however, slowly increases over the same period, such that its overall magnitude remains more-or-less constant:

Seen from mid-Northern latitudes, Mars becomes increasingly difficult to view from around mid-October 2012, the planet appearing low down in the South-west after sunset. Mars attains its most Southerly declination of -24º.55 (i.e. 24.55 degrees South of the celestial equator) on November 18th, when it is in the constellation of Sagittarius, the Archer. From wherever the planet is still visible, it then sets at its most Southerly position along the local horizon (in the WSW from mid-Northern and Equatorial latitudes; towards the South-west in mid-Southern latitudes). Mid-Southern hemisphere latitudes begin to experience difficulty viewing the planet from around mid-December 2012, when it is setting in the WSW about 2 hours after sunset. Equatorial latitudes continue to see Mars with relative ease through to about mid-January 2013, by which time the planet is positioned only 21º East of the Sun.

Mars becomes lost in the twilight glare from all latitudes from around mid-February 2013, when the planet's solar elongation has reduced below 14º. There then follows a prolonged period of non-visibility as the planet continues to head in an Eastward direction on the far side of its orbit from the Earth, returning to the perihelion point in its orbit on January 24th 2013, when it is 1.3814 AU (206.6 million kms / 128.4 million miles) from the Sun. Seen from the Earth, Mars passes behind the Sun - at superior conjunction - on April 18th 2013, although its most distant point from the Earth (the apogee) occurs a fortnight later on June 4th, when it is 2.4665 AU (368.9 million kms / 229.2 million miles) from the Earth and its apparent size is a mere 3".8 across.

The Red Planet becomes visible from the Earth again in the dawn sky from around mid-June 2013, when it is first glimpsed from Equatorial latitudes. This heralds the start of the 2013-14 apparition, which will see Mars in the constellation of Virgo when it next reaches opposition in April 2014.

 [Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]

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Mars Conjunctions with other Planets, April 2011 to February 2013

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.

Alas, most conjunctions involving Mars are unspectacular to view because the planet is usually positioned far away from the Earth - and is therefore not particularly bright - whenever they take place. Those involving Venus will always take place at solar elongations of less than 47° from the Sun, whilst those involving Mercury will always take place at less than about 27° from the Sun. In both of these instances twilight is often a problem, the lighter sky diminishing the visual impact of the conjunction (Mars looking like an ordinary, pale-orange star). Without doubt, Mars' most spectacular conjunctions take place when it is within a few months of opposition - and therefore very bright - at which times they involve either Jupiter or Saturn; these events are however very rare. Most conjunctions between Mars and Jupiter (or Mars and Saturn) occur at elongations of less than 90°, when Mars is far from its brightest in any given apparition. During the 2011-12 apparition, for example, all the visible conjunctions take place at elongations of less than 61°, Mars being fainter than magnitude +1.0 in all cases.

The following table lists the conjunctions involving Mars which take place at solar elongations of 15° or greater. 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.

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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Finding Mars in the Night Sky, September 2011 to August 2012

During the brightest period of its 2011-12 apparition, Mars is easily found using the well-known asterism known as The Big Dipper (or The Plough) in the constellation of Ursa Major, the Great Bear.

Between September and October 2011, when Mars is moving through Gemini and Cancer, the planet can be found using the method shown in the animation here. From November 2011 through to late August 2012, when Mars is moving through Leo and Virgo, observers should use the animation below to help find the planet.

If Mars is some months away from opposition when it is observed, its coloration may not be immediately obvious to the naked eye; in which case, a pair of binoculars will help to reveal its trademark orange colour.

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Bright Stars and Deep-Sky Objects

The seven brightest stars on the star chart are (in order of descending brightness):

• Arcturus ( Boö or Alpha Boötis, magnitude -0.04), an orange-red star in the constellation of Boötes, the Herdsman and the fourth-brightest star in the night sky,
• Procyon ( CMi or Alpha Canis Minoris, mag. +0.4), a yellow-white star in Canis Minor, the Lesser Dog and the fourth brightest Northern celestial hemisphere star,
• Spica ( Vir or Alpha Virginis, mag. ~ +1.0), a blue-white variable star in Virgo, the Virgin,
• Pollux ( Gem or Beta Geminorum, mag. +1.1), a pale orange-yellow star in Gemini, the Twins,
• Regulus ( Leo or Alpha Leonis, mag. +1.3), a blue-white star in Leo, the Lion,
• Castor ( Gem or Alpha Geminorum, mag. +1.6), a blue-white double star in Gemini and
• Alphard ( Hya or Alpha Hydrae, mag. +2.0), a pale orange red giant star in Hydra, the Water Snake.

From mid-January to late April 2012, Mars is brighter than all of the stars shown on the star chart; indeed, it is brighter than both Castor and Alphard throughout the period. The Red Planet is brighter than Procyon from mid-December 2011 to late May 2012, brighter than Spica from mid-November 2011 to mid-July 2012 and brighter than Pollux from late October 2011 to mid-August 2012. The star Regulus, which is positioned not far from Mars during much of the 2011-12 apparition, is exceeded in brightness by the planet from late September 2011 through to the end of the star chart period.

Lying to both North and South of Mars' path through the zodiac from 2011-12 are numerous interesting deep-sky objects (objects beyond our Solar System) which can be seen through small telescopes and binoculars. These will now be discussed, beginning with those contained within the zodiacal band of constellations (in this case, Cancer, Leo and Virgo).

Cancer, the Crab, is a faint and small constellation but it contains numerous interesting objects for the telescopic and binocular observer. Acubens ( Cnc or Alpha Cancri), positioned at the South-eastern end of the constellation's lambda shape (), is the fourth-brightest star in the constellation ( Cancri being the brightest, at mag. +3.5). To the naked-eye, Acubens appears as a star of magnitude +4.3, but a small telescope of aperture 75 mm (3 in) or greater will reveal a faint 12th-magnitude companion (Alpha Cancri B) about 11" away. Acubens (Alpha Cancri A) is itself a double star, its companion being just 0".1 distant - much too close for amateur telescopes to resolve. Alpha Cancri B is also double, making this a quadruple star system. The fainter pair are thought to orbit the primary pair every 6,000 years or so. The Acubens system lies at a distance of about 175 light years from Earth (where 1 light year = 63,240 AU), which means that light from the star takes 175 years to reach the Earth.

Also in Cancer, the star Iota Cancri ( Cnc) is a nice double star of magnitudes +4.0 and +6.5, separated by a relatively wide 30".5, making the two components just visible in binoculars and easily seen through telescopes. Situated about 300 light years away, the brighter star is a golden-yellow giant and the fainter star (positioned to the North-west of the primary) is blue-white.

A short distance to the West of Acubens is the open cluster M67 (NGC 2682) which is rather more densely packed with stars than its more famous companion M44. Details of both of these star clusters (and photographs) can be seen on the page describing the 2009-10 apparition of Mars.

Leo, the Lion is perhaps the most easily recognisable of the zodiac constellations. Representing a Westward-facing crouching lion, its brightest star Regulus ( Leo) marks the position of the animal's heart (the star's alternative name is Cor Leonis, the Lion's heart). Regulus is a double star whose primary component (Regulus A) is magnitude +1.4, with a mag. +7.6 companion (Regulus B) lying some 177" (3 arcminutes) to its North-west. Regulus is another example of a multiple star system; Regulus A has a very close orbiting companion (not visible through amateur telescopes) whilst its fainter companion (Regulus B) is itself double, both of these stars (BC) orbiting the primary once every 130,000 years or so.

Several other double stars in Leo are beyond the ability of binoculars but are easily split in small- or medium-sized telescopes. Algieba (Arabic for 'the lion's mane'), also known as Gamma Leonis ( Leo) is one of the more impressive double stars in the night sky. The primary star has a magnitude of +2.3 and the secondary (mag. +3.5) is positioned 4".7 to the South-east of the primary. Both stars are orange-yellow giants, 126 light years distant from Earth, orbiting each other in a period of about 618 years. Binoculars also show an unrelated 5th-magnitude star (40 Leonis) close by. In 2009 astronomers discovered what they suspect to be a planet orbiting around the brighter star (¹ Leonis). The measurements suggest a planet of around 8.7 Jupiter masses, orbiting the star in a period of about 430 days at a distance of 1.19 AU. Planets orbiting stars outside our Solar System are known as extrasolar planets (or exoplanets); as of mid-2011, over 560 such planets have been detected.

Close to Leo's Northern border with Leo Minor is another double star, 54 Leonis, whose components are magnitude +4.5 and +6.3. The fainter star is positioned 6".6 to the ESE of the brighter. One of the pursuits of many double star observers is tracking down those with significant colour contrasts. However, double star colours are usually very subtle - at the limits of the retina's colour-detection abilities - so that they often appear different for each observer. 54 Leonis is a case in point: it has been described as 'pale blue-green', 'banana yellow', 'greenish-white' and 'whiter than white'!

Mid-way along the lion's hind leg is the double star  Leo (Iota Leonis). It comprises yellow-white components of magnitude +4.1 and +6.7, separated by about 2". The secondary component is currently positioned to the East of the primary and is slowly moving away from it, in a Northward direction. The orbital period is 186 years. Telescopes of 150 mm (6 in) aperture or larger will be able to split the pair.

Situated a little to the North of the lion's fore-leg is an interesting variable star named R Leonis. Its magnitude changes from +4.4 (within naked-eye visibility) sinking to +11.3 (beyond the range of most binoculars) over a period of about 312 days. R Leonis is a red giant variable star of the Mira type (for more details, see the Jupiter 2011-14 page) and it appears distinctly reddish when shining at maximum magnitude.

Leo is home to many dozens of galaxies, although the vast majority are beyond the range of small telescopes. Two of the brighter examples are M65 or NGC 3623 (magnitude +9.5) and M66 (NGC 3627, mag. +8.8) which are positioned only 20' (0°.3) apart. They are not difficult to locate, being approximately mid-way between the stars Coxa ( Leonis, mag. +3.9) and Leonis.  M65 and M66 are about 37 million light years away and they appear relatively bright and elliptical through small telescopes, both of them orientated in a North-South direction. They are just discernible through binoculars in dark, moonless skies as faint, circular hazy patches of light. Also worth tracking down in small telescopes is the relatively bright galaxy NGC 2903 (magnitude +8.9), positioned just to the West of the Sickle of Leo asterism and about 1°.5 South of the star  Leo (Lambda Leonis, mag. +4.3). In a telescopic field of view, the galaxy forms a right-angled triangle with two 7th-magnitude stars. It has a bright central core and appears slightly asymmetric, orientated North-South.

Occupying an area of 1,294 square degrees of the celestial sphere, Virgo is the largest zodiac constellation and the second largest constellation in the entire night sky. It is unsurprisingly home to many interesting astronomical objects. Virgo contains few bright stars but it is plentiful in galaxies. Details of some of the galaxies which are within range of small telescopes and binoculars can be found on the Saturn 2006-13 page.

The star Porrima or Arich ( Vir or Gamma Virginis) is a double star comprising two creamy-white stars of similar magnitude (+3.5) which together appear to the naked-eye as a single star of mag. +2.9. The secondary star revolves around the primary in a highly-elliptical orbit in a period of 169 years. The secondary star came very close to the primary (0".3) in 2005, making the two almost impossible to split, even in large-sized telescopes. They are now separating again and the two components should be discernible through large/medium-sized telescopes after 2012 and through small telescopes after about 2020.

Positioned 6°.7 to the North-west of Virgo's brightest star Spica ( Vir) is the double star  Vir (Theta Virginis). Its two components ( Vir A and  Vir B) are blue-white, of mags. +4.4 and +9.4, the B star being positioned 7".1 to the NNW of the A star. Theta Virginis A has a very close companion star (a spectroscopic binary) which orbits it in a period of about 14 years, but it is too close to be discerned through amateur telescopes. There is also a third component ( Vir C) of mag. +10.4 positioned 69" to the WNW of the A star. The Theta Virginis system is about 415 light years from Earth and is considered to be a good resolving test for a 75 mm (3 in) telescope.

Near the left edge of the star chart, about 7°.1 to the ENE of the star Heze ( Vir or Zeta Virginis, mag. +3.4) is another double star,  Vir (Tau Virginis). The brighter component is mag. +4.3 and the fainter (+9.6) is positioned 80" (1'.3) to the WNW. It is a difficult double for most binoculars but the two components are easily seen through small telescopes. The stars are located about 218 light years from Earth.

Puppis, the Poop, is a Southern hemisphere constellation which is rich in deep-sky objects. It represents the poop (the raised stern section) of the ship named Argo Navis which, in Greek mythology, was captained by Jason to carry his 50-strong crew in search of the Golden Fleece. The Milky Way runs through the constellation, which is the reason why its most numerous deep-sky objects are open star clusters. Puppis lies between declinations -11° and -40° (i.e. between 11° and 40° South of the celestial equator), so that it is only fully visible South of latitude 50° North. At higher latitudes, the Southern section of the constellation is always below the horizon, even when the constellation reaches its highest point above the local horizon at meridian transit.

One open cluster situated in the Northern region of Puppis (at declination = -12°.8) and close to the border with Monoceros is NGC 2539. Its integrated magnitude (i.e. the combined magnitude of all its stars compressed into a single point of light) is about +6.5 and it contains about 130 stars within an area of about 25 arcminutes. Through telescopes, the cluster has an irregular edge and there are about three stellar concentrations of stars of about 10th magnitude and fainter. Through binoculars the cluster is a faint and difficult hazy patch of light.

Hydra, the Water Snake, is the largest constellation in the sky, covering an area of 1,303 square degrees. Only its Northern section is shown on the star chart, this region containing several stars of interest. Alphard ( Hya or Alpha Hydrae, mag. +2.0), also spelled Alfard, is the constellation's brightest star whose isolated position draws attention to an otherwise barren region of the night sky - indeed, its name means 'the solitary one'. Being positioned at the heart of the Water Snake, it has also been known by the name Cor Hydrae. Alphard is an orange giant star 175 light years from Earth. It is the only star in the constellation which shines brighter than magnitude +3.0.

Hydra's most recognisable feature is its head, a distinctive asterism which is located a short distance to the South of the much fainter constellation of Cancer. At the top of the snake's head is the double star  Hya (Epsilon Hydrae) with yellow and blue components of mag. +3.4 and +6.9 respectively. This is one of the more colorful double stars in the night sky, and although the separation between the two components is just 2".7 - making it resolvable only in telescopes of at least 75 mm (3 in) aperture at high magnification - the contrasting colours make it a delight to observe. Epsilon Hydrae is about 135 light years distant, the secondary star orbiting the primary once every 1,000 years or so.

Positioned North of Alphard and a short distance to the West of the star  Hya (Iota Hydrae, mag. +3.9) is the double star ¹ Hya (Tau 1 Hydrae). It is a wide pair (66") of mags. +4.6 and +7.2, the fainter star being positioned to the North of the brighter star. About 1°.7 to the NNE of Tau 1 Hydrae is ² Hya (Tau 2 Hydrae, mag. +4.5). Although the labelling of these two stars might suggest they are in some way connected, they are very different star systems, ¹ Hya lying at a distance of 56 light years from Earth whilst ² Hya lies at a distance of 460 light years. The two stars were originally labelled (and therefore associated with each other) by the Greek mathematician and astronomer Claudius Ptolemy (ca. 90 AD - ca. 168 AD) in his famous Almagest star catalogue, in which he described them as being two "of the three [stars] which are on the bending of the neck [of the Hydra]".

Close to the lower border of the star chart is the variable star U Hydrae, which fluctuates in brightness between mags. +4.7 and +6.2 at irregular intervals. It is a carbon star noted for its deep red coloration; in fact, it is one of the reddest stars in the night sky. Visually, U Hydrae forms a neat equilateral triangle with the stars Hya and Hya (both of which are just outside the star chart coverage).

Close to Hydra's Western border with Monoceros is the open cluster M48 (NGC 2548) which is a pretty sight for binocular and small telescope users. The integrated magnitude is about +5.5, making it just visible to the naked-eye under dark skies. Small aperture telescopes will show about 60 stars within an area of sky about 40' across (greater than the apparent size of the Full Moon). Numerous bright stars and binary stars occupy the centre of the cluster in a North-South alignment. More stars are revealed with increasing telescope aperture; a 30 cm (12 in) telescope, for example, will reveal at least 100 stars across an area of about 50'. The cluster is about 2,000 light years from Earth. When French astronomer Charles Messier published his famous catalogue of non-stellar objects in 1771 (in order to distinguish them from comets) he erroneously listed the declination of Messier 48 to be on the celestial equator, some 5° to the North of its correct position, although the Right Ascension (celestial longitude) he gave for the cluster was correct. Because of the confusion arising from this, credit for the discovery has sometimes been given to the British astronomer Caroline Herschel, who first noted the cluster in 1783.

In the obscure constellation of Lynx, just to the North of Cancer, there are numerous double stars, some interesting (but faint) galaxies and a very distant (and faint) globular cluster. About 2°.4 North of Lynx's brightest star  Lyn (Alpha Lyncis, mag. +3.1) is the double star 38 Lyncis. It is a bright but difficult double owing to the tight separation of its mag. +3.9 and +6.2 components. The sixth-magnitude secondary star is positioned just 2".7 to the South-west of the primary, requiring at least a medium-sized telescope aperture to split them with ease. There is also a third star in the system, of magnitude +10.8, some 88" away, also to the South-west of the primary.

NGC 2683, near Lynx's Southern boundary with Cancer, is the brightest example of the constellation's seventeen or so galaxies which are visible through amateur telescopes. Measuring 9' x 2' on the sky, it is a rather faint edge-on galaxy with an integrated magnitude of +9.7 and a surface brightness of +12.9 (for an explanation of surface brightness in this context, see the Saturn 2006-13 page). NGC 2683 is elongated NE-SW and some dusty features can be glimpsed through larger aperture telescopes.

Much easier to see through telescopes is the Spindle Galaxy (NGC 3115) in Sextans, the Sextant, just to the South of Leo. The integrated magnitude is +9.1 and the surface brightness is +12.6, bringing it within the range of 75 mm (3 in) aperture telescopes or larger. At higher magnifications it appears as a cigar-shaped haze, measuring 8' x 3' in a NE-SW orientation. The galaxy has a bright, elongated core which appears notably stellar in larger telescopes. Thirty-two million light years distant, astronomers class the Spindle Galaxy as a Type S(0) lenticular galaxy, seen edge-on. In 1992 a supermassive black hole was detected at its centre. Apart from its usual designation of NGC 3115, the Spindle Galaxy was also listed by Sir Patrick Moore in his 1995 Caldwell Catalogue as entry number 53 (C53). NGC 3115 should not be confused with another galaxy, NGC 5866 (M102) in the constellation of Draco, the Dragon, which is also known as the Spindle Galaxy.

Ursa Major, the Great Bear, is a large and very well-known constellation which contains the asterism commonly called The Big Dipper (in the USA and Canada) or The Plough (in the UK and Ireland). Only the Southernmost section of the constellation appears on the star chart, where the stars Alula Australis ( UMa or Xi Ursae Majoris) and Alula Borealis ( UMa or Nu Ursae Majoris) are marked. These attractively-named stars are only 1°.6 apart in the night sky and they mark the foot of the Great Bear. Both stars are multiple systems, unrelated to each other.

Alula Australis comprises two yellow components of mags. +4.3 and +4.8 (both of which are spectroscopic binaries), separable only in 75 mm (3 in) or larger aperture telescopes. The secondary star ( UMa B) orbits the primary ( UMa A) in a relatively short period of 60 years and they came closest to each other (0".8) in 1995, when telescopic apertures of 150 mm (6 in) or more were required to split them. As of 2011, the secondary star is positioned 1".6 to the SSW of the primary; by 2020 it will have moved to the SSE of the primary and will be 2".1 distant from it. Alula Australis is a relatively close 27 light years from Earth and it was the first double star to be discovered (by Sir William Herschel in 1780). It was also the first to have its orbit computed (by Félix Savary in 1828).

The components of Alula Borealis are orange and greenish, of mags. +3.5 and +10.1 respectively. The secondary star is positioned 7".2 to the South-east of the primary - another test for a 75 mm (3 in) telescope. At 421 light years from Earth, Alula Borealis is fifteen times more distant than its Southern counterpart. Alula Borealis B is so far away from the primary star (around 950 AU) that it takes at least 12,000 years to complete an orbit. As viewed from the Earth, the orbital motion of Alula Borealis B is so slow that the apparent separation and relative position of the two stars are essentially 'fixed'.

Coma Berenices (Berenice's Hair) is a faint constellation with no star brighter than magnitude +4.3. It does, however, have many faint stars visible through binoculars (in particular, the Coma Star Cluster) and numerous faint, distant galaxies. One of the brighter examples is the Black Eye Galaxy (M64 or NGC 4826), so-named because of a curved dark dust lane which is positioned to one side of its bright central nucleus. This feature does however need a telescope of at least 150 mm (6 in) aperture to be discerned. Under the darkest skies, binoculars will detect the galaxy as a small, faint, slightly elliptical patch of nebulosity. The galaxy measures about 6' x 3', has an integrated magnitude of +8.5 and a surface brightness of +12.6. In larger telescopes, the nebulosity is seen to extend much further away from the galaxy's nucleus. The Black Eye Galaxy is a Seyfert galaxy with an Sb classification (a 'barred spiral') or, more accurately, (R)SA(rs)ab, HIISy2 (!) Astronomers believe that the dark dust lane is a consequence of the galaxy having collided with a passing satellite galaxy at some time in the distant past, the smaller galaxy having been absorbed into the larger. Peculiarly, the galaxy's outer regions rotate in the opposite direction to its inner regions, providing support to the 'collision/absorption' theory. The Black Eye Galaxy is about 24 million light years distant and spans some 65,000 light years across.

Also in Coma Berenices, residing amongst the sprinkling of stars of the Coma Star Cluster, is the galaxy NGC 4494. With an integrated magnitude of +9.9 and a surface brightness of +13, it is rather too faint for binoculars, but small telescopes will show a circular patch of nebulosity with a brighter core. In larger telescopes the nucleus begins to appear stellar, the halo being slightly elongated North-South.

M53 (NGC 5024) is the brightest of three globular clusters in Coma Berenices which are within the range of amateur telescopes. 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. Positioned about 1° to the North-east of the constellation's second-brightest star Diadem ( Com or Alpha Comae Berenicis, mag. +4.3) M53 has an integrated magnitude of +7.5, making it easy to see through binoculars under dark skies. Its apparent diameter is about 13' but it only appears about 3' wide through smaller instruments. It appears as a circular, hazy patch of light with a distinct central core. Telescopes of at least 150 mm (6 in) aperture and high magnifications (over 200x) are required to resolve the centre into individual stars, which are about 11th-magnitude. Through larger instruments (250 mm/10 in aperture or higher) the globular extends to about 12' and the outer regions of the cluster are resolved into stars. M53 is situated about 58,000 light years from Earth, making it one of the more distant globular clusters known in the Milky Way galaxy.

Across the border to the North-east, in the constellation of Canes Venatici, the Hunting Dogs, is another globular cluster, M3 (NGC 5272). It is bright but less easy to find with telescopes than M53. The best technique for telescope users is to aim the finderscope to a position roughly mid-way between Arcturus (in Boötes) and the star Cor Caroli ( CVn or Alpha Canum Venaticorum, not shown on the star chart). As a final guide, a 5th-magnitude star is positioned 1°.5 to the South-west of the cluster. With an integrated magnitude of +6.4 and an apparent diameter of 16', M53 is one of the largest and brightest globular clusters in the Northern hemisphere sky. Through binoculars and small telescopes it appears as a hazy, oval-shaped halo, telescopes showing some granularity at low magnifications. In telescopes of 100 mm (4 in) or higher aperture, the stars in the cluster's outer regions become resolvable. The central core appears somewhat rectangular and slightly off-centre, with curved radial chains of stars emanating from it. M3 is 33,900 light years away and is estimated to contain about half a million stars.

Also in Canes Venatici is the edge-on galaxy NGC 4631, sometimes called the Whale Galaxy. Although not particularly bright, it is worthwhile tracking down because of its unusual, asymmetric appearance. Its dimensions are 15' x 3' and its integrated magnitude +9.2, giving a surface brightness of +13.3. Through telescopes, the galaxy is orientated East-West and has numerous irregular knots and bright spots across its length. The Western end tapers to a point whilst the Eastern end appears rather more rounded, giving it an uncanny resemblance to the giant marine mammal after which it is named. The Whale Galaxy is around 30 million light years distant and is listed as number 32 (C32) in Sir Patrick Moore's Caldwell Catalogue. Just 2'.7 to the North-west of Whale Galaxy is another galaxy, NGC 4627. It is much smaller and fainter than NGC 4631 and requires telescopes of at least 250 mm (10 in) aperture to detect.

Finally, in Boötes, the Herdsman, the globular cluster NGC 5466 is 11' across and has an integrated magnitude of +9.0. Too faint for binoculars, small telescopes show it as a faint, hazy patch about 5' across whilst large telescopes show it extending to about 7' with a slight East-West elongation. NGC 5466 is rather less condensed than most globulars and a 250 mm (10 in) aperture telescope is required to resolve the cluster's outer stars.

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Moon near Mars Dates, May 2011 to February 2013

The Moon is easy to find, and on one or two days in each month, it passes Mars in the sky. The following tables list the dates on which the Moon passes near the planet between May 2011 and February 2013:

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 Mars when seen from some locations than others. For this reason, the dates shown in the table should be used only for general guidance.

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Finding Mars in Your Local Night Sky using AstroViewer^®

Where in the night sky should I look for Mars 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).

The following Javascript program can be used to help find Mars (and any other planets) in your night sky throughout the year:

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The Current Night Sky over Collingwood, Ontario, Canada   Requested by Marley Carroll

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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Mars Meridian Transit Altitudes, 2001 to 2016

Mars is one of only two Solar System planets whose surface details can be seen through modest-sized telescopes (the other being Mercury, whose small size and low altitude often precludes a clear view). 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 consequence, 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.

Mars' meridian transit altitude (as seen from any given point on Earth) varies as the planet drifts Eastwards through the zodiac from one opposition to the next. The meridian transit altitude at which an observer sees a planet is determined not only by the constellation in which the planet is positioned at the time, but also by 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 general, high-Northerly oppositions (in Taurus or Gemini) are best seen from the Northern hemisphere and high-Southerly oppositions (in Scorpius, Ophiuchus, Sagittarius or Capricornus) are best seen from the Southern hemisphere. Mars' last most Northerly opposition took place in Gemini in December 2007, when observers at mid-Northern latitudes saw the planet transit at around 60° to 70° high in the sky, providing optimal conditions for viewing through telescopes. Mid-Southern hemisphere observers fared rather worse, the planet transiting at around 20° to 30° high. Mars' next most Northerly opposition will be in December 2022, when it will be positioned in Taurus (its subsequent opposition in January 2025 will also be high, on the Gemini/Cancer border).

Mars' last most Southerly opposition took place in Ophiuchus in June 2001, when observers at mid-Southern latitudes saw the planet transit at around 70° to 80° high in the sky; mid-Northern hemisphere observers saw it transit at just 20° to 30° high. Mars' next most Southerly opposition will be in July 2018, when it will be positioned in Capricornus.

After the 2001 opposition, observing circumstances for Northern hemisphere observers gradually improved as the planet ascended the ecliptic at each successive opposition. Following its high opposition in Gemini in 2007, the planet began to descend the ecliptic once more, a process which continues through its next four oppositions in Leo (2012), Virgo (2014), Scorpius (2016) and finally Capricornus (2018).

Southern hemisphere observers, having experienced a few rather poor oppositions altitude-wise (in 2005, 2007 and 2010), will see observing circumstances improve over the coming years, the planet appearing further South (i.e. at a higher transit altitude) at each successive opposition.

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Mars Opposition Data, 2001 to 2016

The varying transit altitude of Mars at each opposition is not the only factor which affects the ability to see the planet's surface details through telescopes; there is also the question of its hugely varying apparent size as seen from the Earth. This is the result of the planet's eccentric orbit, which brings it closer to the Earth at some oppositions than at others.

A planet's closest point to the Sun in its orbit is known as its perihelion, and its furthest point from the Sun is called its aphelion. Whenever a planet's opposition occurs close to - or at - its perihelion or aphelion point, it is often referred to as a perihelic opposition or aphelic opposition. Mars' perihelic and aphelic oppositions are particularly significant because its apparent size is considerably different in each case.

Mars' brightest and best oppositions (perihelic oppositions) occur in groups of two or three which repeat in a cycle of about 16 years, when it is closest to the Earth (about 56 million kms / 35 million miles distant). In the opposition of August 2003, when Mars was in Aquarius, the planet came closer to the Earth than it had been for almost 60,000 years; this was largely due to the fact that it reached the perihelion point in its orbit just two days after its opposition date. As seen from the Earth, the apparent equatorial diameter of the Martian disk then reached a sizeable 25".1 (25.1 arcseconds). The next perihelic opposition of Mars will take place in July 2018, in South-western Capricornus, when it will attain an apparent diameter of 24".2 and shine at magnitude -2.8.

In contrast, Mars' present aphelic opposition (2012) sees the planet's apparent diameter attaining just 13".9, a little over half of its perihelic opposition value. This is by far the greatest apparent size variation of any of the superior planets at opposition.

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Star Charts showing Positions of the Planets:

Current Position of the Sun and the Brighter Naked-Eye Planets ('Live' Star Map)

Web Rings

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Credits

• The star chart was created using the commercial software MegaStar by Willmann-Bell, Inc. Star colours were based on those shown in "Patrick Moore's Colour Star Atlas" (Mitchell Beazley Publishers Ltd., London, 1973).
• The planetary conjunction dates, times and separations of the lunar conjunctions with Mars (Moon near Mars dates) and the lunar phases were obtained from the commercial software RedShift 5 by Maris Technologies Ltd. using the 'Conjunctions' option of the 'Sky Diary'.
• The dates of Mars' apogee and perigee and their distances were derived from the SETI Institutes' Mars Ephemeris Generator 2.2, with supplementary data from the SkyGazer Ephemeris utility by John Biondo. The constellation boundary crossing dates were obtained from RedShift 5.

• The zodiac signs are courtesy of the free graphics site .

Copyright © Martin J Powell  July - August 2011