The Mars Apparition of 2006-2008
by Martin J. Powell
The path of Mars against the background stars of Taurus, Gemini and Cancer from August 2007 to May 2008, shown at 15-day intervals (click for full-size image, 242 KB). During the 2006-8 apparition, Mars described a more typical looping formation, quite unlike that of its last apparition in 2004-6, when the planet described a zigzag (or 'Z-shaped') formation in Aries.
The star map applies to observers in the Northern hemisphere (i.e. North is up); for the Southern hemisphere view, click here (252 KB; the Southern hemisphere chart should be used by observers situated south of the Tropic of Cancer [23½° North]). The Milky Way is shown in dark grey; the faintest stars shown on the map have an apparent magnitude of about +4.4. Printer-friendly versions of this chart are available for Northern (182 KB) and Southern hemisphere (189 KB) views.
Following superior conjunction on October 23rd 2006 (when it passed directly behind the Sun) Mars emerged in the dawn sky in December 2006 as a relatively dim 'morning star', rising shortly before the Sun. Through the first half of 2007, the planet was best viewed from the Southern hemisphere. For Northern hemisphere observers, viewing circumstances were poor from late 2006 and throughout the first half of 2007, with Mars appearing low down in the Eastern sky at dawn. Mars became a prominently visible object from the Northern hemisphere around July 2007, by which time it was rising some three hours or so before the Sun. Viewing circumstances improved for both hemispheres as 2007 progressed.
From late 2006 through to November 2007, Mars moved steadily eastwards (i.e. direct motion) through the following constellations, slowly brightening as its distance from Earth reduced:
Table showing the position and apparent magnitude of Mars for the early part of the 2006-2008 apparition (click for full-size image, 25 KB). The apparent magnitude listed here refers to the point when the planet is at the centre of the constellation shown (data from 'MegaStar'). Mars began the apparition descending the ecliptic (i.e. heading Southwards) from Virgo through to Sagittarius, then ascended the ecliptic (heading Northwards) from Capricornus through to Taurus. 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.
Mars began to brighten significantly from late August/early September of 2007 and reached opposition (i.e. its brightest for this apparition) on the night of December 24th 2007. Note that, although opposition took place on this date, Mars' closest approach to the Earth (at 0.5893 Astronomical Units or 88.15 million kms) took place a little earlier - on December 19th - because of its eccentric orbit.
With an apparent magnitude of -1.6 and a maximum apparent disk diameter of 15.8 arcseconds, Mars was not as bright nor as large (when seen through a telescope) as it was at its previous opposition in November 2005, when the planet reached magnitude -2.3 and had an apparent diameter of 20.1 arcseconds. This reduction in apparent size and brightness will continue at the next two oppositions, culminating in Mars' aphelic opposition in Leo in 2012.
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For much of the period displayed in the above map, Mars was brighter than all of the stars shown, with a handful of exceptions. Capella ( Aur or Alpha Aurigae, apparent magnitude +0.08) exceeded Mars in brightness prior to late September 2007 and did so again after late February 2008; Betelgeuse ( Ori or Alpha Orionis, mag. +0.5v) and Procyon ( CMi or Alpha Canis Minoris, mag. +0.38) exceeded Mars in brightness after early March 2008 and Aldebaran ( Tau or Alpha Tauri, mag. +0.85) was brighter than the planet from early April 2008.
On opposition day (which co-incided with Christmas Eve in the Christian calendar), Mars was joined by the Full Moon, which passed close by the planet during the early morning hours (see Moon near Mars dates below). For Northern hemisphere observers, the planet was then due South at local midnight (due North at local midnight in the Southern hemisphere).
For Northern hemisphere observers, the 2007 Mars opposition saw the planet appear about as high as it can get in the sky at meridian transit (due South) providing optimal viewing conditions for telescopic observers, though this was rather offset by its less-than-favourable apparent size.
Telescopic observing conditions in the Southern hemisphere were less favourable, since there the planet appeared at its lowest possible angular elevation when at meridian transit (due North).
Table of selected data relating to the brighter part of the Mars apparition of 2006-8 (click for full-size image, 59 KB). Mars reached opposition at the most Northerly part of the ecliptic - namely, on the Taurus-Gemini border - providing good viewing conditions for Northern hemisphere observers. Data from 'SkyGazer Ephemeris' and 'MegaStar'.
Mars faded rapidly after opposition as its distance from Earth increased, but it remained visible for some 11 months in the evening sky, slowly closing in on the setting Sun. From May 22nd-23rd 2008, the planet crossed the star cluster known as Praesepe (pronounced 'pree-SEE-pee') which is visible to the naked eye as a hazy patch of light (it is also known as Messier 44 , 'The Manger' or 'The Beehive Cluster' because of its binocular resemblance to a cloud of swarming bees). The planet's furthest distance from Earth for this apparition (2.5033 AU or 374.49 million kms) was reached on October 31st 2008, when its apparent diameter was a mere 3.7 arcseconds across. By late November 2008, Mars became lost from view in the dusk twilight.
Table showing the location and apparent magnitude of Mars for the latter part of the 2006-2008 apparition (click for full-size image, 13 KB). As the apparition drew to a close, Mars once again headed Southwards along the ecliptic, moving from Cancer through to Ophiuchus. Data from 'MegaStar'.
Mars passed behind the Sun - at superior conjunction - on December 5th 2008. The 2009-2010 apparition began soon afterwards, which saw Mars in the constellation of Cancer when it next reached opposition on January 29th 2010 (for details, see the Mars 2009-10 page).
[Terms in yellow italics are explained in greater detail in an associated article describing planetary movements in the night sky.]
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Moon near Mars Dates,
August 2007 to May 2008
The Moon is easy to find, and on one or two days in each month, it passes Mars in the sky. The following table lists on which dates the Moon passed near the planet between August 2007 and May 2008:
Moon near Mars dates for the period from August 2007 to May 2008 (click for full-time image, 24 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 (times are Universal Time [UT], equivalent to GMT). The Moon Phase shows whether the Moon was waxing (between New Moon and Full Moon), waning (between Full Moon and New Moon), at crescent phase (less than half of the lunar disk illuminated) or gibbous phase (more than half but less than fully illuminated).
The Moon moves relatively quickly against the background stars in an Eastward direction, at about its own angular width (0º.5) each hour (about 12º.2 per day). 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 have appeared 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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Rise/Transit/Set Directions Table
The directions in which Mars rises, transits and sets depends upon the constellation in which Mars appears at the time, and also on the observer's latitude. To find the rising/transiting/setting direction of Mars for your own location, refer to the following table and look up the directions for the nearest appropriate latitude:
Rise, transit and set directions of Mars during 2007-08 for a variety of latitudes (click for full-size image, 51 KB). The Meridian Transit Altitude is the angular altitude of the planet when on the observer's meridian. When a celestial body crosses the observer's meridian (known as the meridian transit or culmination), it has reached its greatest angular altitude in the sky. Hence at latitude 40º North on March 10th 2008, Mars rose in the NE, transited the meridian (crossed the due South point) at its highest altitude of about 76º (i.e. about four-fifths of the way up the sky) and set in the NW.
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Copyright Martin J Powell November 2006
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