The Mars Apparition of 2015-2017
by Martin J Powell
The Path of Mars against the background stars of the Southern zodiac from December 2015 to October 2016, shown at 10-day intervals (click on the thumbnail for a full-size image, 203 KB). During this apparition Mars describes a Southward zig-zag formation against the background stars, unlike the 'hybrid' loop that it described during the planet's previous apparition in 2013-15. The path of Saturn in Southern Ophiuchus is also marked at the beginning of each month over the same period; the two planets pass each other in the evening sky in late August 2016 (for more details see the planetary conjunctions section below). The star map applies to observers in the Northern hemisphere (i.e. North is up); for the Southern hemisphere view, click here (208 KB).
The faintest stars shown on the map have an apparent magnitude of about +4.8. Printer-friendly versions of this chart are available for Northern (95 KB) and Southern hemisphere (96 KB) views. Astronomical co-ordinates of Right Ascension (longitude, measured Eastwards in hrs:mins) and Declination (latitude, measured in degrees North or South of the celestial equator) are marked around the border of the chart. Click here (156 KB) to see a 'clean' star map of the area (i.e. without planet path); observers may wish to use the 'clean' star map as an aid to plotting the planet's position on a specific night - in which case, a printable version can be found here (78 KB). Night sky photographs of the Southern zodiac constellations can be seen below.
At superior conjunction on June 14th 2015 (when it passes directly behind the Sun in the constellation of Taurus), the planet Mars is positioned 2.5675 Astronomical Units (AU) from Earth (384.1 million kms or 238.6 million miles). Were it to be visible from Earth at this time, it would have an apparent magnitude of +1.5 and an apparent size of only 3".6 (i.e. 3.6 arcseconds, where 1" = 1/60th of an arcminute or 1/3600 of a degree). Mars enters the constellation of Gemini, the Twins, on June 25th. On July 11th the Red Planet reaches its most distant point from the Earth for this apparition (sometimes referred to as the apoareion), a distance of 2.5869 AU (386.9 million kms or 240.4 million miles). The planet now shines at an apparent magnitude of +1.6 and has an apparent diameter of 3".6. Mars enters Cancer, the Crab, on August 5th, at which time it is positioned 15° West of the Sun.
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The Red Planet's 2015-17 apparition truly begins as it emerges into view from the bright dawn twilight around late July, when it is seen rising in the Eastern sky from Northern Tropical latitudes. In early August Mars is rising in twilight across the inhabited world, pulling away from the Sun at a rate of just 0°.3 per day. The planet is visible for a period of time which is dependant upon the observer's latitude and the local season. Mars rises 1½ hours ahead of the Sun at latitude 50° North, 1¼ hours before the Sun at 40° North, 1 hour before sunrise at the Equator and only 45 minutes before sunrise at latitude 35° South.
Around mid-August Mars is moving steadily Eastward against the background stars at a rate of about 0°.6 per day. From mid-Southern latitudes Mars begins to appear in the dawn sky around this time, when Mars is passing through the star cluster known as Praesepe (pronounced 'PRE-SEEP-EE'), designated Messier 44 (M44 or NGC 2632). It is also known by the names Beehive Cluster or The Manger. Mars passes through Praesepe over a 40-hour period from 18 hours UT on August 19th to 10 hours UT on August 21st. However, being just 20° from the Sun, only observers at Northern Tropical latitudes are able to view it (a few degrees above the ENE horizon), and even then for a short period of time.
At this early stage in the apparition, Mars appears as a feeble, pale-orange star, shining about as bright as the star Castor ( Gem or Alpha Geminorum, mag. +1.6), the second-brightest star in Gemini. Mars barely gains any significant altitude (angle above the horizon) before disappearing into the brightening dawn twilight. Telescopically the planet is a disappointing sight, its low altitude and tiny apparent size (ca. 3".7) frustrating most attempts to obtain a steady and clear view of the planet's surface.
Mars in April 2014 imaged by Spanish amateur astronomer Joaquin Camarena using a 12-inch Schmidt-Cassegrain telescope fitted with a CCD camera (click on the thumbnail for a larger image, 4 KB). Mars had just passed its closest point to the Earth during its 2013-15 apparition. Compare this image with a sketch drawn by British astronomer Paul Abel below (Image: Joaquin Camarena /ALPO-Japan).
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On August 22nd Mars passes between the two Ascelli in central Cancer - namely, the stars Asellus Borealis ( Cnc or Gamma Cancri, mag. +4.6) and Asellus Australis ( Cnc or Delta Cancri, mag. +3.9). The planet passes 1°.1 North of Asellus Australis and 2°.2 South of Asellus Borealis, i.e. at about one-third of the distance between them. On August 27th the planet passes 6°.4 North of the star Acubens ( Cnc or Alpha Cancri, mag. +4.2) at the South-eastern corner of the constellation's lambda-shaped () pattern.
In late August Mars experiences the first of six planetary conjunctions which take place during the planet's 2015-17 apparition. A planetary conjunction takes place whenever any two planets attain the same celestial longitude in the night sky. Venus, shining at magnitude -4.2, is entering the morning sky at the start of its 2015-16 apparition as a 'Morning Star', becoming visible at dawn from around August 20th. Venus is slowly retrograding (moving East to West) in the South-eastern corner of Cancer whilst Mars is moving more speedily in the opposite direction several degrees to the North. The two planets cross the same longitude (Right Ascension = 9 hours 3 minutes) on August 29th, Venus being a sizeable 9°.4 to the South of the Red Planet. Mars has faded slightly to magnitude +1.7 and the pair are positioned some 22° West of the Sun at this time.
Mars leaves Cancer and heads into Leo, the Lion, on September 5th, passing 5°.2 North of the star Subra ( Leo or Omicron Leonis, mag. +3.5) at the tip of the Lion's foreleg, on September 13th. Between September 15th and 29th Mars is positioned South of the asterism known as the Sickle of Leo, at the Western end of the constellation, which appears to the naked-eye as a backward question-mark (). Using this analogy, Leo's brightest star Regulus ( Leo or Alpha Leonis, mag. +1.4) is in the position of the dot.
Mars has faded by about 0.3 magnitudes since the start of the apparition three months earlier. On September 17th Mars attains its faintest apparent magnitude of the apparition, at just +1.8. The planet now lies at a distance of 2.4521 AU from the Earth (366.8 million kms or 227.9 million miles) and its apparent diameter has increased slightly to 3".8. By this time the planet is rising in darkness from across the Northern hemisphere. Mars rises 3 hours ahead of the Sun at latitude 60° North, 2¼ hours before the Sun at latitude 40° North and 1½ hours before the Sun at the Equator. At Southern Tropical latitudes Mars rises in darkness about 1¼ hours before sunrise whilst at mid- and high-Southern latitudes the planet rises in twilight only an hour before sunrise. The planet's position in Western Leo means that it rises in the ENE from most of the inhabited world, with the exception of high-Northern latitudes (i.e. further North than about 55° North) where the planet rises in the North-east.
On October 17th Mars passes 0°.4 North of Jupiter in the second planetary conjunction of the Martian apparition. Jupiter, at mag. -1.6, has emerged into the dawn sky in the early stage of its 2015-16 apparition. The two planets are positioned 40° West of the Sun at the moment of conjunction, with Venus (mag. -4.3) located 6°.6 to the West of the pair. For more details of this and the other planetary conjunctions taking place during this apparition, refer to the planetary conjunctions section below.
The following day (October 18th) Mars is involved in a rare occultation of a naked-eye magnitude star. At around 1924 UT the Red Planet occults the star Leo (Chi Leonis, mag. +4.7), situated just ahead of the Lion's rear paw. The event, which lasts a maximum of about 2½ minutes, is visible in darkness from the Eastern seaboard of China, South Korea, Japan, the Southern Philippines (Mindanao) and Eastern Indonesia (Halmahera, Irian Jaya).
Over the next fortnight Mars, Jupiter and Venus form a variety of geometric shapes in the night sky, clustered in Southern Leo, the two brightest naked-eye planets providing good pointers to the slowly-brightening Red Planet. On October 20th the three planets form an East-West line some 5°.7 long, just South of the Lion's body. On October 23rd the three form a low, flat isosceles triangle measuring 4°.6 wide at the base with sides 2°.3 long. Mars passes 0°.3 South of the star Leo (Sigma Leonis, mag. +4.0), at the foot of the Lion's hind leg, on October 25th. At around 03 hours UT on the following day (October 26th) Mars, Jupiter and Venus form another isosceles triangle, this one lying on its side with a base measuring 1° wide and with sides of 3°.5. The triangle points East, towards the constellation of Virgo. Venus reaches its greatest Western elongation (46° West of the Sun) at 10 hours UT on the same day. On October 28th the three planets form another isosceles triangle, grouped around the Lion's rear paw, this time with a base 4°.6 wide and sides of 2°.5; this triangle is just 0°.9 high.
Mars enters Virgo, the Virgin, on November 2nd. In the early hours (UT) on November 3rd the three planets form a long, 6°.9-high isosceles triangle, 0°.7 wide at the base, the apex pointing WNW towards Regulus. At around 16 hours UT on the same day Venus, moving direct (Eastwards) at an apparent daily rate of 0°.9 against the background stars, passes 0°.7 to the South of slower-moving Mars in the third planetary conjunction of the apparition. The two planets are positioned 46° West of the Sun, Venus having hardly changed its solar elongation since attaining greatest elongation eight days previously.
Mars' passage through the constellations during the early part of the 2015-17 apparition (i.e. pre star chart) is summarised in the table below:
Table showing the position and apparent magnitude of Mars for the early part of the 2015-17 apparition (click on the thumbnail for the full-size table, 22 KB). The magnitudes, diameters and solar elongations listed here refer to the middle of the period in question. In this and the tables which follow, the rising and setting directions of the constellations listed can be found by referring to the zodiacal constellation rise-set direction table.
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By November 5th Mars and Venus have pulled sufficiently Eastwards from Jupiter so that no more geometric formations take place between the three. However, Mars, Venus and the star Zavijah ( Vir or Beta Virginis, mag. +3.6) form an interesting straight line at around 17 hours UT on November 5th. The line, 1°.8 in length, is small enough to be contained within a telescopic wide-field (low magnification) eyepiece view and easily within a binocular field-of-view. Mars passes 0°.8 North of Zavijah itself on November 8th, then crosses the celestial equator (where the declination of a celestial body is 0°) heading Southwards on November 18th.
By mid-November, Mars has escaped the twilight and is rising in darkness from across the inhabited world, its solar elongation having reached 51°W. The Red Planet now rises around 5½ hours before the Sun at latitude 60º North; 4¼ hours before sunrise at 40º North; 3¼ hours before sunrise at the Equator and 2¼ hours before sunrise at 35º South. Since Mars now lies close to the celestial equator, it rises very close to due East across the inhabited world. At 60° North the planet attains a respectable 27° altitude before the dawn twilight envelops it. At 40° North the planet attains an altitude of 38°; at the Equator it reaches 39° whilst at 35° South the planet reaches just 18° high.
Mars reaches its most distant point from the Sun (called its aphelion) on November 20th, at a distance of 1.666 AU (249.2 million kms or 154.8 million miles).
Over the next month Mars passes the brighter stars which make up the Southern part of the Virgo figure, the planet entering the star chart coverage (above) in late November. On November 21st the planet passes 4° North of the star Zaniah ( Vir or Eta Virginis, mag. +3.8) then 1º.4 South of the double star Porrima or Arich ( Vir or Gamma Virginis, mag. +3.5) on December 1st.
In the early hours of December 6th the waning crescent Moon passes close by Mars and, in some regions of the world, passes in front of the planet (thereby blocking it from view) in an event called a lunar occultation. This particular occultation is seen in darkness from North-eastern Africa, Southern Arabia and the North-western Indian Ocean. From Addis Ababa in Ethiopia, Mars disappears behind the Moon's bright limb at about 0015 UT (0315 local time) and re-appears from behind the dark limb 1¼ hours later, at 0130 UT (0430 local time), the pair being positioned around 30º above the Eastern horizon (also see the Moon near Mars Dates section below).
By the end of the first week in December, the Red Planet has brightened to the upper threshold of second magnitude (+1.5) and its apparent diameter has increased to just under 5". Mars passes 0º.3 South of the star Theta Virginis ( Vir, mag. +4.4) on December 14th. One week later (December 21st) it passes 3º.8 North of the constellation's luminary named Spica ( Vir or Alpha Virginis, mag. +1.0), Mars being about 0.3 magnitudes fainter than the bright, blue-white star.
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As 2016 commences the Red Planet has reached a solar elongation of 70° West and has brightened to magnitude +1.0. As Mars enters Libra, the Balance, on January 17th, it is moving fractionally slower against the background stars (at 0°.5 per day) than at the commencement of the apparition some five months earlier. Mars passes 1°.2 North of the constellation's second-brightest star Zuben Elgenubi (2 Lib or Alpha2 Librae, mag. +2.8) on February 1st. At around 0930 UT on the same day, the Last Quarter Moon, Mars and the double-star Zuben Elgenubi form an interesting line-up measuring 2°.9 across.
Mars reaches western quadrature (90° West of the Sun) on February 7th, positioned 2º.8 ENE of Zuben Elgenubi. When seen from the Earth, the planet now shows its minimum phase (in this case, 90%) making it appear slightly gibbous when seen through telescopes. The illuminated section of the disk faces Eastwards, i.e. towards the Sun. The Martian disk appears 7" across and shines at magnitude +0.7. Across the inhabited world, Mars is now rising in the ESE a little over 6 hours before sunrise. The altitudes attained by the planet before its dawn disappearance are: 13° (at 60° North), 33° (at 40° North), 74° (at the Equator) and 65° (at 35° South). Between latitudes 10º North and 75º North, the planet transits the local meridian (i.e. it passes through its highest point in the South) a short while before disappearance. South of 10º North, the dawn twilight washes out the planet before it reaches the meridian. Mars is now brightening significantly with each passing week, its pale-orange coloration seemingly more obvious than in the preceding months. Also on February 7th, Mars passes 9º.4 North of the star Brachium or Zuben Algubi ( Lib or Sigma Librae, mag. +3.3).
Mars reaches magnitude +0.5 on February 19th, technically making it a zeroth-magnitude object. On February 25th the planet passes 3º.1 South of the star Zuben Elakrab ( Lib or Gamma Librae, mag. +4.0) and then 2º.2 South of the star Theta Librae ( Lib, mag. +4.1) on March 7th. Mars passes 3º.2 North of Dschubba ( Sco or Delta Scorpii, mag. +2.2), in the neighbouring constellation of Scorpius, the Scorpion, on March 12th, the planet attaining magnitude -0.0 ('minus zeroth magnitude') on the same day.
Mars enters Scorpius on March 13th, reaching 10".0 in angular diameter three days later, positioned about 115° West of the Sun. For telescopic observers, the planet is now at a sufficient apparent size for significant surface detail to be seen and for a regular campaign of observing to commence.
Mars passes just 8' (8 arcminutes, where 1' = 1/60th of a degree) North of the double-star Graffias (1 Sco or Beta-1 Scorpii, combined mag. +2.6) on March 16th. The two blue-white components (1 Sco and 2 Sco) are magnitudes +2.6 and +4.9, separated by 13".7 and are easily seen in small telescopes. Beta-1 Scorpii is itself also double, having atenth-magnitude companion positioned less than an arcsecond away, separable only in larger telescopes. The Mars-Graffias passage is best seen from North-west Africa, Southern Europe, the Atlantic Ocean and the Eastern half of South America. A simulated telescope view of the event is shown in the graphic below.
Mars passing near the double-star Graffias (click on the thumbnail for the full-size animation, 67 KB). On March 16th 2016 Mars passes eight arcminutes North of the star Graffias (1 Scorpii), seen here near the top of this simulated telescope view. The planet's position is shown about 2 hours before the moment of closest approach at 4 hrs UT. South is up and East is to the right; the field of view is about 13'.
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Over the course of eleven hours on March 17th, the planet passes North of the two Omegan stars Jabhat al Akrab (1 Sco or Omega-1 Scorpii, mag. +3.9) and Omega-2 Scorpii (2 Sco, mag. +4.3). The two stars are separated in the night sky by 0º.24 and they lie very close to the ecliptic (the path of the Sun, which the Moon and planets follow very closely). Consequently, one or other of these stars is often occulted (hidden from view) by the Moon and, much more rarely, by planets (Venus will next occult 2 Sco in the year 2038). On this occasion, Mars passes 0º.9 North of the blue-white star Jabhat al Akrab (Arabic for 'forehead of the Scorpion') at 05 hours UT and 1º.1 North of the yellow star Omega 2 Scorpii at 16 hours UT.
Situated a few degrees to the North-east of the two Omegan stars is the star Jabbah ( Sco or Nu Scorpii, mag. +4.0). It is a quadruple star, i.e. it appears as a blue-white double-star through small telescopes, but larger telescopes reveal each of its component stars to be double. Mars passes 0º.5 South of Jabbah on March 21st.
On March 26th Mars, now at magnitude -0.4, passes 2º.6 North of the eighth-magnitude globular cluster M80 (or NGC 6093) which, like most of the brighter globulars, appears as a faint, circular, fuzzy spot of light through binoculars under dark skies. The narrow separation allows the two objects to be contained within the eyepiece view of a wide-field, low-magnification ocular, whilst binocular users will see the planet and cluster appear in very close proximity.
Now approaching the Eastern border of Scorpius, Mars passes 5º North of the variable star Alniyat ( Sco or Sigma Scorpii, mag. +2.9) on March 31st, the planet now having brightened to magnitude -0.5 ('minus first magnitude') and its apparent daily motion having slowed dramatically to just 0º.1. Mars enters Ophiuchus, the Serpent-Bearer, on April 3rd, a constellation which is famous (or rather, infamous!) for its absence from the astrological list of zodiac constellations. Its original name was Serpentarius, although today this is almost never used. Ophiuchus is a large, unwieldy constellation, occupying 948 square degrees of sky, but only its narrower, Southern section is crossed by the ecliptic.
By mid-April the planet has brightened a further half-magnitude to -1.0. On April 17th Mars' Eastward (direct) motion ceases when it reaches its eastern stationary point, positioned 5º.2 North of the Scorpion's brightest star Antares ( Sco or Alpha Scorpii, mag. +1.0v). Hereafter the planet's motion becomes retrograde (Westward), a situation which will continue over the next 2½ months. Antares is unmistakable in that it scintillates (twinkles) orange-red, rivalling the colour of the Red Planet - indeed, the name Antares derives from the ancient Greek 'anti Ares' meaning 'rival of Mars' (Ares being the ancient Greek God of War). The two celestial bodies' brightnesses differ on this occasion by two magnitudes, Antares being obviously the fainter of the two.
Table of selected data relating to the brighter part of the Mars apparition of 2015-17 (click on thumbnail for full-size table, 159 KB). The data is listed at 10-day intervals, corresponding with the dates on the star map.
The Central Meridian Longitude (provided for telescopic observers) is the Martian longitude which appears at the centre of the disk when seen from the Earth at the time indicated (0h Universal Time, or 0h GMT). A Martian longitude map by Damian Peach showing the surface features can be seen at the BAA Mars Section website (note that the map is shown with South up, matching the inverted view seen through astronomical telescopes). For example, when CM = 290°, Syrtis Major appears at the centre of the disk. The Central Meridian Longitude increases by 14°.6 every hour, so this allowance should be applied for observations at other times (if the result is greater than 360°, subtract 360° to obtain the correct longitude).
Those wishing to observe Mars telescopically should consider downloading the free 'Mars Previewer II ' software by Leandro Rios, available as a ZIP file at Sky & Telescope.
The data for the table was obtained from 'RedShift 5', 'MegaStar 5', 'SkyGazer Ephemeris' , 'Mars Previewer II' software and Mars Ephemeris Generator 2.5. The Martian disk images were derived from NASA's Solar System Simulator v4. The Martian disks appear at the same scale as those in the Mars Opposition data table here.
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Mars crosses the ecliptic in a Southward direction on April 28th, positioned close to Ophiuchus' Western border with Scorpius. The planet's ecliptic crossing at this point is significant because it determines the shape of the loop described during the months around its opposition. Essentially, whenever a superior planet crosses the ecliptic near the time of its opposition to the Sun, the path described by the planet against the background stars will take the form of a zig-zag, i.e. either an 'S-shape' or a 'Z-shape' (as opposed to the standard loop). The zig-zag will be Northward-facing ('Z-shaped') when the planet moves to the North of the ecliptic and Southward-facing ('S-shaped') when it moves to the South of the ecliptic. In the present situation - as can be seen in the star chart above - Mars describes a Southward-facing zig-zag over the period in question (for more information on the loops and zig-zags described by the planets in the night sky, see the Planet Movements page).
From around late April, with the planet's elongation having increased to around 140º, the lengthening Northern summer twilight begins to interfere with observation from latitudes North of about 60º North. In early May, observers at 60º North are only able to view the planet for about 4 hours, the entire visible period taking place in advanced twilight.
Mars moves back into Scorpius on April 30th and soon afterwards begins to pass the stars it had already passed in the previous two months, except in reverse order. Mars passes 3º.9 North of Alniyat ( Sco) on May 3rd; 1º.2 North of the globular cluster M80 on May 7th and 2º.2 South of Jabbah ( Sco) on May 11th. On May 15th Mars passes the two Omegan stars 1 Sco and 2 Sco again; 0º.8 South of 2 Sco at 04 hours UT and 1º.0 South of 1 Sco at 14 hours UT. May 16th sees the planet passing 1º.8 South of Graffias ( Sco) and May 20th sees it pass 0º.9 North of Dschubba ( Sco).
At 2022 UT on May 21st the Full Moon passes several degrees to the North of a now very bright Mars (mag. -2.0), an event which provides an excellent opportunity for astrophotographers. Due to the effect of parallax, the angular separation between the two celestial bodies will depend upon the observer's location on Earth. The separation between Mars and the Moon varies on this occasion from 5º.1 (at higher Northern latitudes) to 6º.5 (at mid-Southern latitudes), the best views of the pairing being from Southern Europe, the Middle East, Southern and Eastern Africa, India and the Indian Ocean (also see the Moon near Mars Dates section below).
Mars reaches opposition to the Sun at 11 hours UT on May 22nd 2016, at which point it is directly opposite the Sun in the sky (solar elongation = 180°) and at its brightest for this apparition. The planet is positioned 1º.3 WNW of Dschubba, 4º.8 South of Theta Librae ( Lib) and 8º.8 North-west of Antares. This is not, however, Mars' closest point to the Earth during this apparition; because of the eccentricity of its orbit, Mars' periareion (its closest point to Earth) is reached eight days later - on May 30th - when it is 0.5032 AU distant (75.2 million kms or 46.7 million miles), i.e. about 935,600 kms (581,300 miles) closer than on opposition day. The Red Planet now shines at magnitude -2.05 and its apparent size is 18".3, i.e. double the size it was in early March and triple the size it had been in mid-January. On opposition day Mars is creeping slowly Westward against the stars of Scorpius at a rate of about 0º.3 per day.
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; 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, the Red Planet is experiencing late Summer in its Northern hemisphere and late Winter in its Southern hemisphere. The planet's Northern polar axis is tipped towards the Earth at an angle of about 10º, giving us a good view of its Northern Polar Cap (NPC). Mars is positioned at a heliocentric longitude of 241º ( = 241°) and the areocentric longitude of the Sun (Ls) is 156°. The Martian Year is 33, the Martian Month is 6 and opposition day equates to Sol Number 330 on Mars. The equivalent Earth date on Mars - called the Martian Date (MD) - is September 19th. All the terms given in this paragraph are explained in more detail on the Martian seasons page.
At the 2016 opposition, Mars is 0.6 magnitudes brighter (nearly two times brighter) than it was at its previous opposition in April 2014 and its apparent disk diameter is about 20% larger. Mars has almost ended its run of poor (i.e. distant) oppositions which have resulted in small disk diameters (less than about 20" across) since the opposition of December 2007. 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. The 2016 opposition of Mars is, however, a relatively good one, lying in the middle-ground between an aphelic and a perihelic opposition (for more details, see the Mars Oppositions page).
Opposition having passed, the solar elongation moves from Westerly to Easterly and the magnitude of the angle reduces. Mars' solar elongation reduces from 180° (on opposition day) to 170° East of the Sun one week later, on May 29th. Mars passes 4º.8 South of Theta Librae ( Lib) for a second time on May 24th. The planet's retrograde motion carries it back into Libra itself on May 28th, reaching periareion (see above) two days later. On June 6th Mars passes 6º.3 South of Zuben Elakrab ( Lib), reaching its western stationary point, 5º.4 NNE of Brachium ( Lib), on June 30th. The planet's motion now returns to 'normal' (direct) and continues as such through the remainder of the apparition.
Seen from high-Northern latitudes, the 'visibility window' of Mars has been rapidly closing and from early July, observers North of about 60º North lose sight of the planet completely in the bright summer twilight, which now lasts throughout the night. Observers in these high latitudes do not see Mars again until late September, by which time the planet has moved on South-eastwards to the Southernmost point of the zodiac.
Now moving direct and having faded to magnitude -1.0, Mars once again passes the stars it has already passed (twice) since late February. Although occupying the same band of Right Ascension (celestial longitude) as it did five months earlier, the wide and open 'S-curve' described by the planet has now placed it over 4º further South than it was back then. Hence on July 25th the planet passes 7º.4 South of Zuben Elakrab ( Lib), some 4º.3 further South than its February 25th passage (see above).
Mars re-enters Scorpius on August 2nd, passing 6º.4 South of Theta Librae ( Lib) on August 6th. Again, this is 4º.2 further South than its March 7th passage of this star and 1º.6 further South than its May 24th (retrograde) passage. On August 10th the planet passes 0º.8 South of Dschubba ( Sco), a full 4º further South than its March 12th passage of this star and 1º.7 further South than its May 20th (retrograde) passage. On both of these previous occasions Mars was positioned to the North of Dschubba, whereas it is now to the South of it.
By mid-August Mars has faded back to 'minus zeroth magnitude' (-0.5) and its apparent diameter has shrunk by a third since opposition. On August 12th the planet passes 3º.9 South of the double-star Graffias ( Sco) once more, then on the following day encounters the Omegan stars 1 Sco and 2 Sco again, on this occasion at a wider separation than previously. Mars passes 3º.1 South of 1 Sco at 12 hours UT and 2º.9 South of 2 Sco at 19 hours UT.
Mars passes 1º.2 South of the globular cluster M80 on August 18th, the same distance from the cluster that it passed whilst moving North of it on May 7th. Finally, the planet passes 1º.2 North of Alniyat ( Sco) on August 20th, its solar elongation having now reduced below 100º.
On August 21st, Mars re-enters Ophiuchus. Over the next five days the planet passes a globular cluster, a red giant star and a ringed planet. Soon after crossing the border Mars passes 2º.1 North of the globular cluster M4 (NGC 6121), a 7th-magnitude cluster in Scorpius which is visible through binoculars under truly dark skies. Being so close to Antares it is easy to find and, being some 20' in diameter, is wonderfully resolved through telescopes. It is not a particularly concentrated cluster but has an eye-catching central 'bar' of faint stars running vertically through its centre.
Prior to 2016, Mars last reached opposition in April of 2014 (click on the thumbnail to see the full-size version, 92 KB). This photograph of the event, taken by the author, shows the Red Planet's position among the stars of Virgo one day after opposition day. Mars (at magnitude -1.4) was positioned about 2º.5 North of the ecliptic, a little to the North-east of the star Theta Virginis (mag. +4.4). The constellation's brightest star Spica (mag. +1.0) is the bright star to the SSE of Mars, near the bottom of the picture. Click here (76 KB) to see an annotated version of the photograph.
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On August 24th Mars passes 1º.8 North of Antares ( Sco) itself, providing a good opportunity to compare the colours of the two objects by naked-eye. Now at magnitude -0.4, Mars is 1.4 magnitudes (around 3½ times) brighter than the star which, one could argue, does not really make for a fair comparison. The situation is made more difficult by the fact that Mars, being a planet, shines with a steady light, whilst Antares, being a stellar point-source, scintillates considerably (paricularly from higher Northern hemisphere latitudes, where the star transits at a low elevation).
Mars experiences its fourth planetary conjunction of the apparition on August 25th, when it passes 4º.4 South of Saturn. This wide conjunction is best seen from the Southern hemisphere, the planets differing by 0.9 magnitudes. The event takes place in late summer in the Northern hemisphere, positioning the two planets low above the South-western horizon at dusk and poorly placed for observation. Saturn has faded since reaching opposition the previous June although its wide-open rings continue to make it a nice telescopic sight.
At around 18 hours UT on August 27th Mars re-enters Scorpius at a shallow angle to the North-east of Antares, returning to Ophiuchus six days later on September 2nd.
Mars passes 0º.8 North of the seventh-magnitude globular cluster M19 (NGC 6273) on September 6th. At around 12' in diameter, it is a roughly oval-shaped 'fuzzball' of stars which can easily be seen through binoculars and small telescopes.
Mars reaches eastern quadrature (90º East of the Sun) on September 13th, positioned 11º.1 East of Antares. Like at western quadrature back in February, the planet again shows a minimal phase - in this case, 84% - making it appear slightly gibbous when seen through telescopes. Unlike at western quadrature, the illuminated part of the planet's disk faces Westwards (not Eastwards, as before) because it is now positioned to the East of the Sun when seen from the Earth.
On September 14th Mars passes 0º.7 South of Ophiuchus' Southernmost bright star Theta Ophiuchi ( Oph, mag. +3.2), leaving the constellation on September 22nd when it enters Sagittarius, the Archer. Now four months after opposition, the planet is moving a tad faster against the background stars than it was four months before opposition. Back in mid-January the planet was moving Eastwards at a rate of 0°.53 per day but now it is moving Eastwards at 0°.64 per day; so the planet exited the 'S-curve' at a faster speed than it entered.
By the third week of September the planet's apparent diameter has reduced to just 9".3 - only half that at its closest approach back in late May. Mars attains its most Southerly declination for this apparition, at -25° 54' 37" (-25°.91 in decimal format) on September 23rd, which is the furthest South the planet has been positioned since 2001. The planet now sets at its most Southerly position on the local horizon. Typically this will be towards the South-west at latitudes far away from the Equator and towards the WSW at Equatorial latitudes. Mars now sets 2 hours after the Sun (at 60º North), 4¼ hours after the Sun (40º North), 5¾ hours after the Sun (Equator) and 7 hours after the Sun (35º South).
By late September Mars' apparent magnitude has returned to positive (+0.0). Between September 28th and 29th, it passes 1º.5 South of the sixth-magnitude gaseous nebula labelled M8 (NGC 6523) and commonly called the Lagoon Nebula. With an apparent dimension of 90' by 40', the planet takes 29 hours to traverse the width of the nebula (from 11 hours UT on September 28th to 16 hours UT on the 29th). The planet is now seen amidst the backdrop of a very star-rich region of the Milky Way galaxy, only 5º degrees away from its true centre.
From around late September, observers situated North of ca. 60º North, who lost sight of the planet in mid-July, now begin to detect it once more, low down in the SSW after sunset.
Over the next few weeks Mars passes the numerous bright stars which define the shape of Sagittarius' Archer figure, along with four globular clusters, which are particularly numerous in this region of the night sky. Between September 29th and October 19th the planet passes just to the North of the constellation's famous asterism, the Teapot. It is bounded by eight stars (which taken counter-clockwise are: Nash, Kaus Meridionalis, Kaus Borealis, Phi Sagittarii, Nunki, Tau Sagittarii, Ascella and Kaus Australis). The Teapot is supposedly pouring its contents over the tail of the Scorpion and the steam rising from its spout is said to be marked by a particularly dense and misty stretch of the Milky Way. The path of Mars on this occasion just clips the top of the teapot.
On September 29th Mars passes 4º.6 North of the star Nash or Al Nasl ( Sgr or Gamma Sagittarii, mag. +3.0). At around 2050 UT on the following day the planet passes just 4'.8 (4.8 arcminutes) North of the 8th-magnitude globular cluster NGC 6553 (apparent diameter 8'.1), a cluster which is only seen well in larger telescopes. On October 4th the planet passes 4º.1 North of the star Kaus Meridionalis ( Sgr or Delta Sagittarii, mag. +2.7) which marks the centre of the Archer's bow. The next day (5th) Mars passes 0º.8 South of another globular cluster, M28 (NGC 6626), of 7th-magnitude and with an apparent diameter of 11'.2. On October 7th Mars passes just 11' (11 arcminutes or 0º.2) South of the orange star Kaus Borealis ( Sgr or Lambda Sagittarii, mag. +2.8) which marks the top of the Teapot asterism (and incidentally, the top of the Archer's bow, which points West). At 0320 UT on October 8th the Red Planet passes a mere 3'.5 (3.5 arcminutes or 0º.05) South of the faint, 9th-magnitude globular cluster NGC 6638 (visible in darkness from the Eastern Pacific Ocean and its seaboard). This is another difficult and concentrated globular, 5' in diameter, which is only well resolved in larger optical instruments (a simulation of the view through an astronomical telescope is shown below). On October 9th the planet passes 1º.5 South of the much brighter globular cluster M22 (NGC 6656) which is considered to be one of the finest globulars in the night sky. Its integrated magnitude is about +5.9 and it has an apparent diameter of 24'. It is just visible to the naked-eye from dark sites, is easily seen through binoculars and is a spectacular sight through telescopes.
Mars passing near Globular Cluster NGC 6638 (click on the thumbnail for the full-size animation, 94 KB) October 8th 2016 the Red Planet passes a few arcminutes away from the 9th-magnitude globular cluster (positioned at the centre of this simulated telescopic view). The planet's position is shown at about 2 hrs UT, closest approach taking place about an hour later. South is up and East is to the right.; the field of view is about 25 arcminutes.
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The four stars passed by Mars over the next week form the 'handle' of the Teapot. The planet passes 1°.7 North of Phi Sagittarii ( Sgr, mag. +3.1) on October 13th; 1°.2 North of the constellation's second-brightest star Nunki ( Sgr or Sigma Sagittarii, mag. +2.0) on October 16th; 5°.0 North of Ascella ( Sgr or Zeta Sagittarii, mag. +2.6) on October 18th and finally, 3º.0 North of Tau Sagittarii ( Sgr, mag. +3.3) on October 19th.
Now clear of the brighter stars of Sagittarius, Mars continues on its Eastward course, passing 1°.3 North of 52 Sagittarii (mag. +4.6) on October 29th and, on the same day, reaching perihelion (its closest orbital position to the Sun) at a distance of 1.3812 AU (206.6 million kms or 128.4 million miles) from the Sun. On November 7th the planet passes 5°.4 North of the star Terebellum (62 Sgr, mag. +4.5), at the far Eastern edge of the constellation. Shortly afterwards, the planet exits the star chart coverage.
There are simply too many globular clusters in Sagittarius for Mars to leave the constellation without passing another one(!) and so, at 04 hours UT on November 8th, the planet passes 13' (13 arcminutes) South of M75 (NGC 6864). This distant and compact 8th-magnitude cluster has an apparent diameter of only 6' and lies just 0°.3 from the Eastern edge of the constellation. Ten hours later Mars leaves Sagittarius and enters Capricornus, the Sea-Goat.
Mars passes 6º.4 South of the star Dabih ( Cap or Beta Capricorni, mag. +3.0) on November 13th and 0º.9 South of Theta Capricorni ( Cap, mag. +4.0) on November 27th. On December 3rd, at about 0817 UT, the planet passes a very close 44".7 (44.7 arcseconds) South of the star Iota Capricorni ( Cap, mag. +4.3). This is so close together that the naked-eye cannot split the two; they effectively appear as one 'star'. Through binoculars and telescopes at low magnification the pair appear as a temporary 'double-star' with components of magnitude +0.7 and +4.3, Iota Capricorni appearing pale yellow and Mars, of course, pale orange. On December 9th, Mars passes 1º.3 North of Nashira ( Cap or Gamma Capricorni, mag. +3.7) and finally, on December 11th it passes 1º.4 North of the constellation's brightest star, a variable star named Deneb Algiedi ( Cap or Delta Capricorni, mag. +2.9v).
By the middle of December Mars is setting around 6 hours after the Sun at latitude 60º North, 5 hours after the Sun at latitude 40º North, 4½ hours after sunset at the Equator and 4 hours after sunset at latitude 35º South. Being positioned some 10º South of the celestial equator, the planet sets in the WSW across the inhabited world. The altitudes of the planet, as it becomes visible in the dusk twilight, are: 16° (at 60° North), 35° (at 40° North), 55° (at the Equator) and 38° (at 35° South). Between latitudes 56° North and 76° North Mars transits soon after it appears in the dusk twilight; elsewhere, the planet has already passed the meridian when it is first glimpsed.
The Red Planet enters Aquarius, the Water-Carrier, on December 15th, passing 1º.0 North of the star Iota Aquarii ( Aqr, mag. +4.2) on December 18th. Four days later (22nd) Mars passes 4º.0 South of the star Ancha ( Aqr or Theta Aquarii, mag. +4.1). Between December 23rd and 28th the planet is positioned about 10º South of Aquarius' best-known identifier, the so-called 'Steering Wheel' asterism (a star chart showing this region of the night sky can be found on the Neptune page).
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With the arrival of 2017, Mars is involved in its closest planetary conjunction with Neptune for over seven centuries! At 0637 hours UT on January 1st Mars, now at magnitude +0.9 and less than 6" across, passes just 1'.2 (1.2 arcminutes or 0º.02) South of Neptune, at mag. +7.9. The closeness of the two planets - easily contained within the field-of-view of telescopes at high magnifications - makes it an ideal opportunity for those who have never seen our most distant Solar System planet to locate it with relative ease, using Mars as a bright locator-beacon. This most proximate of evening conjunctions is ideally placed for Northern hemisphere observers, the two planets being positioned 58º away from the Sun.
Two days later, at 0511 hours UT on January 3rd, the five-day old waxing crescent Moon, Mars and Neptune form a tight trio 1º.4 across in central Aquarius. The trio is not wholly naked-eye of course (since Neptune is involved) however this is a potentially interesting grouping to observe through small telescopes at low magnification. The grouping is best seen from the central Pacific Ocean, where the Moon is also seen to occult (block from view) the two planets in turn. From the islands of Kaua'i (Hawaii) and Necker Island (Leeward Islands), where it is evening on January 2nd (local time), a lunar occultation of Neptune is in progess as dusk falls. Neptune re-appears in darkness behind the bright limb of the Moon, then two hours later the dark limb of the Moon occults Mars. Thirteen hours after this interesting event - the Moon now having moved on North-eastwards - Mars passes 0º.4 South of the star Lambda Aquarii ( Aqr, mag. +3.9).
On January 11th the planet passes 0º.4 North of the star Phi Aquarii ( Aqr, mag. +4.2) and, on January 13th, 1'.7 (1.7 arcminutes or 0º.02) North of the star 96 Aquarii (96 Aqr, mag. +5.7). Both of these stars lie quite close to the ecliptic and, like the Omegan stars in Scorpius (see above), they are sometimes occulted by passing planets. Phi Aquarii will next be occulted by Venus in the year 2028 and 96 Aquarii will next be occulted by Mars in 2032.
From January 12th through to the 23rd, Mars, now mag. +1.0, is positioned about 7º South of the Circlet of Pisces, at the Western end of Pisces, the Fishes. The Circlet comprises six stars of fourth and fifth magnitude; under light-polluted conditions it is likely that some or all of them will not be seen with the naked-eye. Mars enters Pisces on January 19th.
From around the third week of January, Venus approaches Mars from the West, though the two planets do not reach conjunction on this occasion. Venus is now about three-quarters of the way through its 2016-17 evening apparition and reached its greatest Eastern elongation (its maximum angle East of the Sun) on January 12th. Over the next few weeks Venus curves against the stars to the West of Mars, moving from direct to retrograde motion, initially getting closer to Mars but then pulling away from it. Venus is positioned 6º.6 to the WSW of Mars on 21st January, 5º.4 West of it from February 2nd-3rd (its closest point to the Red Planet) and 5º.9 to its WNW on February 10th.
A sketch of Mars drawn by British amateur astronomer Paul Abel in April of 2014 (click on the thumbnail for a larger image, 4 KB). In an age dominated by high-tech imaging equipment, much useful scientific work can still be obtained visually by acquiring good observational skills. Abel's sketch compares very favourably with a CCD image of Mars taken around the same time (see above) (Image: Paul G Abel /ALPO-Japan).
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Mars crosses the celestial equator ( = 0°) heading Northwards on January 29th, positioned to the South-east of the Circlet of Pisces. The planet's apparent diameter falls below 5" on February 3rd. Mars briefly exits Pisces at 01 hours UT on February 7th when it enters the constellation of Cetus, the Whale, clipping its North-western corner. Over the next 11½ hours Mars is technically outside the zodiac, traversing a stretch of Cetan sky just 0º.3 wide (measured South-east to North-west) before re-entering Pisces at 12 hours UT on the same day. This translates into a daily apparent motion of about 0º.6 against the background stars.
Mars passes 2º.5 South of the star Delta Piscium ( Psc, mag. +4.4), about half-way along the Southern Fish's body, on February 15th and then 1º.2 South of the star Epsilon Piscium ( Psc, mag. +4.3) on February 20th. At 1233 UT on February 24th the planet passes just 11'.6 (11.6 arcminutes or 0º.2) North of Zeta Piscium ( Psc), a double-star with components of mag. +5.6 and +6.5, separated by a distance of 22".8. Much like the planet's close passage of Iota Capricorni ( Cap) on December 3rd 2016 (see above), Mars, now at mag. +1.2, appears to the naked-eye as the brighter component of a 'double-star', the fainter component (i.e. Psc) itself appearing as a single white star of mag. +4.9. The separation of the two (11'.6) is nearly the same as that between the stars Mizar ( UMa or Zeta Ursae Majoris, mag. +2.0) and Alcor (80 UMa, mag. +4.0), the famed double-star in Ursa Major, positioned at the bend of the Big Dipper's 'arm'. Mizar and Alcor have historically been considered a good test of one's eyesight, since the limit of the average naked-eye's acuity is generally thought to be about 5' (5 arcminutes, or 0º.08).
At around 05 hours UT on February 27th Mars crosses the ecliptic heading Northwards, then just 3½ hours later passes 0º.6 North of the planet Uranus in the Red Planet's last planetary conjunction of this apparition. Much like its conjunction with Neptune in January, this evening conjunction in Pisces is ideally placed for Northern hemisphere observers, although the narrower solar elongation (43º East) means that the two planets are positioned slightly lower in the sky after sunset and are visible for a shorter period before they set. At magnitude +5.9 Uranus is at the limit of naked-eye visibility whilst Mars has faded to mag. +1.3. The two are close enough to be contained within a wide-angle telescope eyepiece view, and are easily seen in binoculars.
Seen from latitudes South of about 43º South, Mars' narrowing solar elongation, its low altitude and the local twilight reduce the 'observing window' of the planet to just 1½ hours from around late February. Elsewhere the planet is now setting 4½ hours after the Sun (at latitude 60º North), 3½ hours after sunset (at 40º North), 2½ hours after sunset (at the Equator) and about 1¾ hours after sunset (at 35º South). Mars sets in the WNW in the Northern hemisphere and in the West in the Southern hemisphere. At latitude 60° North Mars stands 26° above the horizon when it first becomes visible at dusk - a significant improvement on previous months, caused by the improved angle of the ecliptic to the local horizon after sunset. Elsewhere the altitude of the planet is beginning to fall as its solar elongation falls below 45°. At 40° North it is 33° high at dusk; at the Equator it stands 32° high whilst at 35° South it is only 14° above the horizon.
At around 04 hours UT on March 8th, Mars passes 1º.8 North of the star Torcularis Septentrionalis ( Psc or Omicron Piscium, mag. +4.2) in the tail of the Northern Fish. The fanciful name, which is Latin for 'North Press', first appeared in the 1515 edition of the star catalogue Almagest. It was a translation of the Greek word '' meaning 'winepress'. However, this was a mistranslation of the original Greek word '' meaning 'flax', i.e. the cord that tied the two fishes' tails together.
Ten hours after passing Torcularis, Mars enters the constellation of Aries, the Ram. The planet passes 7º.4 South of the double-star Mesarthim ( Ari or Gamma Arietis, mag. +3.9) on March 11th and later that same day, 8º.7 South of the star Sheratan ( Ari or Beta Arietis, mag. +2.6). Aries' brightest star Hamal ( Ari or Alpha Arietis, mag. +2.0) is passed by the planet five days later (March 16th) at an angular distance of 10º.3. Mars' uneventful passage through this small constellation continues with the passage of two fourth-magnitude stars in the Eastern half of the Ram: 3º.8 to the South of Epsilon Arietis ( Ari, mag. +4.6) on April 3rd and 1º.4 South of Botein ( Ari or Delta Arietis, mag. +4.3) on April 8th. The following day, Mars fades below the threshold of second magnitude, at +1.5.
Mars enters Taurus, the Bull, on April 12th - although the Red Planet is not quite done with Aries yet. Two days later, at about 0310 UT, it leaves Taurus and re-enters Aries, traversing a WSW-ENE path just 5'.5 (5.5 arcminutes) long. A little over three hours later, at 0620 UT, Mars re-enters Taurus; this equates to an apparent daily motion of 0º.7 against the background stars. The planet is now only 30º from the Sun, has an apparent magnitude of +1.5 and an apparent diameter of just 4".
Between April 19th and 21st Mars passes around 3°.5 South of the constellation's most famous star grouping known as the Pleiades (pronounced 'PLY-add-eez' or 'PLEE-add-eez'), also called the Seven Sisters (Messier 45). The cluster would normally make for an interesting photographic subject, however its low altitude at dusk severely limits the observing time. As they become fully visible the Pleiades stand between 7° high (at 60° North and 25° South) and 13° high (at 30° North) in the North-west (60° North) or the WNW (elsewhere). The orientation of the cluster - and the Red Planet's position in relation to it - varies according to the observers's latitude. Around latitude 9° North Mars and the cluster appear at roughly the same elevation at dusk; North of this latitude, the cluster is positioned to the upper-right of the planet, whilst South of this latitude it is positioned to the lower-right. South of ca. latitude 27° South the Pleiades are too low down to observe at this time.
From around late April, twilight begins to interfere with observation of Mars as seen from latitudes North of ca. 60° North. At these latitudes the planet is visible for around 3 hours before setting in the North-west, the planet being in twilight throughout. Elsewhere the planet is setting in darkness towards the WNW. At latitude 40° North, Mars sets about 2¼ hours after sunset and at the Equator it sets around 1¾ hours after sunset. At mid-Southern latitudes the planet sets just 1¼ hours after the Sun.
During the first week of May, Mars passes around 5°.3 North of a much larger star cluster called the Hyades. The group was rather too widely scattered to form part of Charles Messier's catalogue, so it has no Messier number, however it is sometimes referred to under the moniker of Melotte 25 (after the British astronomer Philibert Jacques Melotte, who published his catalogue of 215 globular and open clusters in 1915). The Hyades is a distinct 'V'-shaped grouping of stars which form the head of the Bull. At the apex of the 'V' is a star known variously as Prima Hyadum, Primus Hyadum or Hyadum I ( Tau or Gamma Tauri, mag. +3.6). The name means 'First Hyad' or 'Chief of the Hyades', the Hyades being the daughters of Atlas and Aethra in Greek mythology. Mars passes 6°.5 North of the star on May 1st. Hyadum II (1 Tau or Delta-1 Tauri, mag. +3.7) is a triple star system positioned roughly mid-way along the Northern arm of the 'V' (the Bull's forehead). Its name means 'Second Hyad' (therefore, linguistically it should be named Secundus Hyadum). Mars passes 4°.7 North of this star on May 2nd.
At the South-eastern corner of the Hyades, marking the 'eye' of the Bull, is the orange-red star Aldebaran ( Tau or Alpha Tauri, mag. +0.9). Its coloration derives from the fact that it is a red giant star. Most of the Hyades stars comprise a genuine cluster, moving through space together, however Aldebaran is not part of the group; it is a foreground star, positioned closer to the Earth than the cluster. Mars passes 6°.2 North of Aldebaran on May 7th.
At 1144 UT on May 9th the Red Planet makes another close passage of a star: this time, just 24".7 (24.7 arcseconds or 0'.4) North of the triple-star Tau Tauri ( Tau, mag. +4.2), which is positioned at the 'bend' of the Bull's Northern horn. The distance between planet and star equates to just six apparent Mars-diameters, although the Red Planet is eleven times brighter than the star. Tau Tauri A is a blue-white star with a seventh-magnitude white or lilac companion, Tau Tauri C, positioned just over 1' (1 arcminute) away to its South-west (Tau Tauri B is an eighth-magnitude companion of the primary star, too close for amateur telescopes to split). Interestingly, the distance at which Mars passes the primary star (Tau Tauri A) is a little over one-third of the apparent distance between Tau Tauri A and Tau Tauri C, although unfortunately in this instance, the planet and Tau Tauri C are not in the same direction.
Around mid-May, observers situated at high Northern and Southern latitudes are the first to bid farewell to the Red Planet as it slips into the dusk twilight. Over the next two weeks the 2015-17 Martian apparition also closes for observers situated North of about 45° North.
On May 24th Mars passes 4°.5 South of the star Al Nath or El Nath ( Tau or Beta Tauri, mag. +1.6) which marks the tip of the Bull's Northern horn. The star also carries the name Gamma Aurigae ( Aur) since, apart from defining one of the Bull's horns, it also neatly completes the six-sided figure comprising the stars of Auriga, the Charioteer, located to the North-east of Taurus. The star marking the tip of the Bull's Southern horn is Zeta Tauri ( Tau, mag. +2.9v) and Mars passes 3°.0 North of it on May 28th. With its return to the vicinity of North-eastern Taurus, Mars has now completed a full circuit of the zodiac since the start of its 2015-17 apparition nearly two years earlier.
On June 5th the Red Planet enters Gemini, the Twins, and one day later it attains its most Northerly declination for this apparition ( = +24° 19' 43" or +24°.32). For those latitudes which can still see it, the planet now sets at its most Northerly point along the local horizon, the actual point of setting depending upon the observer's latitude. By the end of the first week of June Mars only remains visible between latitudes 40° North and 30° South, setting towards the WNW throughout.
Mars' passage through the constellations during the latter (i.e. post star chart) period of the 2015-17 apparition is summarised in the table below:
Table showing the position and apparent magnitude of Mars for the latter part of the 2015-17 apparition (click on thumbnail for full-size table, 32 KB). As in the first table, the magnitudes, diameters and solar elongations refer to the middle of the period in question.
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As Mars' solar elongation reduces below 15º East of the Sun in mid-June, the planet finally becomes lost from view from across the inhabited world, bringing the 2015-17 apparition to a close. Mars remains out of view - lost in the solar glare - for around 2½ months as it continues Eastwards on the far side of its orbit from the Earth. Mars reaches superior conjunction (passing behind the Sun as viewed from the Earth) in Western Cancer on July 27th, when it is 2.6553 AU (397.2 million kms or 246.8 million miles) from Earth. Were the planet visible from Earth at this time, it would shine at magnitude +1.7 and appear just 3".5 across.
Mars becomes visible from the Earth again in the Eastern sky at dawn from around late August 2017, when it is first glimpsed from Northern Tropical latitudes. This heralds the start of the much-awaited 2017-19 apparition, which will see Mars pass at its closest point to the Earth since 2003 when it next reaches opposition in Capricornus in July 2018.
[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,
2015 to 2017
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 planetary conjunction or an appulse. However, not all planetary conjunctions will be visible from the Earth because many of them take place too close to the Sun. Furthermore, not all of them 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 2015-17 apparition, for example, all except one of the six visible conjunctions take place at elongations of less than 58°, Mars being fainter than magnitude +0.8 in all five cases.
Four of the six conjunctions favour the Northern hemisphere, these being evenly divided between morning and evening viewings. Rather unusually, Mars has no visible conjunctions with the planet Mercury during this apparition.
The most interesting Martian conjunction of the 2015-17 apparition is that with Saturn in the evening sky on August 25th 2016. Taking place in Southern Ophiuchus just three months after both planets' opposition dates, it is also the brightest of the six conjunctions, Mars and Saturn being at either end of 'zeroth magnitude'. This is the only conjunction of the six which truly favours the Southern hemisphere. At the moment of their first appearance at dusk, the two planets are positioned at the zenith (directly overhead) at 25° South, 80° above the Northern horizon at 35° South and 70° above the Northern horizon at 45° South. Despite the relatively wide solar elongation of 97°, twilight and low altitude interfere with observation from mid- and high-Northern latitudes. This is caused by the dual effect of the planets' high Southerly declinations and the shallow angle of the ecliptic to the local horizon after sunset at this time of year. On this occasion Mars and Saturn are separated by a wide 4º.4, so that they are too far apart to fit within a telescopic field of view but are well within the typical view of binoculars. In 2016 the pair only narrowly miss out on multiple conjunction events (i.e. double or triple conjunctions) because the planets' loops do not overlap in longitude.
There are two conjunctions with Venus during the apparition, both being morning events in 2015. The conjunction of November 3rd is ideally placed for Northern hemisphere observers, the planets' location in Virgo positioning the ecliptic at a steep angle to the local horizon at dawn. This conjunction is less well-seen in the Southern hemisphere, being visible in twilight at around 35° South and not visible at all South of latitude 49° South. A poor, nine-degree wide conjunction between Venus and Mars at dawn on August 29th is only visible South of mid-Northern latitudes and North of mid-Southern latitudes.
Mars is involved in a close morning conjunction with Jupiter in central Southern Leo on October 17th 2015. Seen from the Northern hemisphere, the planets reach a respectable altitude in the Eastern sky before the Red Planet succumbs to the dawn twilight. At latitude 50° North the planets attain an altitude of 27° before Mars is lost from view whilst at 20° North they reach 31°. Adding brilliance to the event, shining at magnitude -4.3, is morning star Venus, positioned 6½° away to the West of the pair. The conjunction is seen in twilight from mid-Southern latitudes, reaching only 16° above the horizon at latitude 25° South and just 8° at 40° South.
The final two conjunctions of the apparition - with the ice giants Uranus and Neptune - are both evening events which are favourable to Northern hemisphere observers. With a separation of just 1.2 arcminutes (0°.02), Mars' Jan 1st 2017 conjunction with Neptune is its closest with this planet since the year 1289, at which time Edward I was King of England and the Crusader state of Tripoli, Lebanon had recently fallen to the Muslim Sultan Qalawun of Egypt. This is academic, of course, since the conjunction could not have been observed by the citizens of the thirteenth century. Some 320 years would pass before the invention of the telescope (which is required to see Neptune) and a further 236 years would pass before Neptune itself was discovered!
Whilst Mars is an obvious telescopic or binocular object, eighth-magnitude Neptune is eighteen times further away than the Red Planet in January 2017 and 630 times fainter, so it has to be sought out from the smattering of background stars. Mars can easily be spotted in the dusk twilight but Neptune typically requires up to 45 minutes of additional time before the sky is dark enough for the planet to be seen through binoculars. Consequently the altitude of the two planets falls considerably by the time both of them can be seen together. When they become visible, the pair are placed 20° high in the SSW at 60° North and 43° high in the SSW at 20° North. In the Southern hemisphere, the pair are placed 38° high in the West when they become visible at 15° South and 23° high in the West at 35° South.
The Mars-Neptune conjunction of January 2017 is the Red Planet's closest passage to any planet since August 1989; its next closest passage will be with Mercury in the year 2032. Whilst this is a relatively unspectacular conjunction to observe, it is worthwhile doing so if only for its historical rarity; Mars will not come any closer to Neptune until the year 2100.
The last conjunction of the 2015-17 apparition takes place on February 27th 2017, when Mars passes 0º.6 to the South of Uranus in Eastern Pisces. The circumstances applying to Neptune (above) also apply here except that, since Uranus is six times brighter than its more distant twin, it requires less time to become visible in the twilight. At higher latitudes, Uranus requires an extra 20 minutes or so to become visible after Mars has first been glimpsed in the twilight. When the pair become visible in the WSW after sunset, they stand 22° high at 60° North and 31° high at 20° North. Twilight and low altitude prevent visibility of this conjunction at latitudes South of about 45° South.
The following table lists the conjunctions involving Mars which take place at solar elongations of 15º or greater. Where other planets are also in the vicinity, details are given. Note that, because some of the conjunctions occur in twilight, the planets involved may not appear as bright as their listed magnitude suggests.
Mars conjunctions with other planets from August 2015 to February 2017 (click on thumbnail for full-size table, 59 KB). 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 Mars, e.g. on 2015 Nov 3, Venus is positioned 0°.7 South of Mars at the time shown. The 'Fav. Hem' column shows the Hemisphere in which the conjunction is 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 view 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 are 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.
A table of planetary conjunctions involving Mars from 2016 to 2020 can be seen here (67 KB).
Although any given conjunction takes place at a particular instant in time, it is worth pointing out that, because of the planets' relatively slow daily motions, such events are interesting to observe for several days both before and after the actual conjunction date.
There are in fact two methods of defining a planetary conjunction date: one is measured in Right Ascension (i.e. perpendicular to the celestial equator) and the other is measured along the ecliptic, which is inclined at 23½° to the Earth's equatorial plane (this is due to the tilt of the Earth's axis in space). An animation showing how conjunction dates are determined by each method can be found on the Jupiter-Uranus 2010-11 triple conjunction page. Although 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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The Southern Zodiac: Constellation Photographs
Sagittarius & Southern Zodiac
Libra & Northern Scorpius
Virgo, Libra, Scorpius, Ophiuchus and Sagittarius (click thumbnails for full-size versions: 183 KB, 57 KB and 65 KB) Photographs showing the region of the night sky through which Mars passes during the year following December 2015. Small, annotated versions of the photographs can be seen for the Virgo photo (12 KB), the Libra & Northern Scorpius photo (12 KB) and the Sagittarius photo (20 KB). The regions of the star chart which are visible in the photographs can be seen by clicking on the thumbnail (left, 69 KB). In the Virgo photo, stars are visible down to an apparent magnitude of about +7.5; in the Libra & Northern Scorpius photo the limiting magnitude is about +7 whilst that of the Sagittarius photo is about +8.1. Note that the three photographs do not have the same scale because of the differing 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).
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Finding Mars in Your Local Night Sky
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).
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Moon near Mars Dates,
August 2015 to May 2017
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 August 2015 and May 2017:
Moon near Mars dates for the period from August 2015 to May 2017 (click on thumbnail for full-size table, 109 KB). The Date Range shows the range of dates worldwide (allowing for Time Zone differences across East and West hemispheres). Note that the Date, Time and Separation of 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. All times are Universal Time [UT], which is equivalent to GMT. The Sep. & Dir. column gives the angular distance (separation) and direction of the planet relative to the Moon, e.g. on May 21st 2016 at 20:22 UT, Mars is positioned 6°.0 South of the Moon's centre. The Moon Phase shows whether the Moon is 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).
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 may 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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Mars Meridian Transit Altitudes,
2001 to 2020
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 continued through its next two oppositions in Leo (2012) and Virgo (2014) and also at its next opposition in Scorpius (2016).
Southern hemisphere observers, having experienced a few rather poor oppositions altitude-wise (in 2005, 2007 and 2010), will see observing circumstances improve over the next few years, the planet appearing further South (i.e. at a higher transit altitude) at both the 2016 and 2018 oppositions.
Meridian Transit altitudes of Mars at successive oppositions from 2001 to 2020, as seen from a variety of latitudes (click on thumbnail for full-size table, 53 KB).
The planet's best (brightest) oppositions take place when it is positioned in Aquarius, as it was in 2003. During these times Southern hemisphere observers benefit from a high transit altitude; conversely, observers at mid-Northern latitudes must contend with less-than-ideal transit altitudes (< 35°). Observing circumstances improved for Northern hemisphere observers after the planet's 2001 opposition (when it was positioned at a high-Southerly declination in Ophiuchus) but they began to worsen after 2007.
Meanwhile, the Martian disk as seen through the telescope shrank after the 2003 opposition but began to increase from the 2014 opposition (see Mars Opposition section below).
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. For more details, see the Mars oppositions 2012-2027 page.
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Copyright © Martin J Powell June 2015
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