Mercury offers its best evening show of the year for northern hemisphere observers when it reaches greatest eastern elongation - 18 degrees east of the Sun - on March 5th. At this time the innermost planet will set up to two hours after sunset, shinning at magnitude -0.3. Telescopically the apparent disk size is 7.2 arcseconds and the phase, visible even in small telescopes, is just less than half illuminated.
It should be possible to follow Mercury for the first half of the month until it is lost in the Suns glare. For southern hemisphere observers the elongation is not nearly as favourable, Mercury is extremely low in the dusk sky, sets only half an hour after the Sun and hence a challenging object to locate.
A few days earlier on March 2nd Mercury is at perihelion and only 46 Million km (0.307 AU) distant from the Sun.
Venus is a blazing evening object as it heads towards greatest eastern elongation of 46 degrees on March 27th. The planet will be in Pisces for the first few days of March before spending the majority of the month in Aries and finally ending the month in Taurus. It is undoubtedly at its brilliant best, beginning March at magnitude -4.2, ending it at magnitude -4.4 and visible for a good few hours each evening. When viewed from the northern hemisphere, Venus sets over 4 hours after sunset. It is visible from mid-southern hemisphere latitudes for not quite so long, but still a respectable couple of hours or so. Either way, Venus is an unmistakable beacon this month shining above the western horizon just after sunset.
On March 15th, Venus will overtake Jupiter in the sky. At closest approach the two planets will be separated by just over 3 degrees.
The apparent size of Venus increases from 18 arcseconds at the beginning of the month to 24 arcseconds at the end.
It's a good month for observers of the red planet as Mars reaches opposition on March 3rd and hence is visible all night. Due to the orbits of the Earth and Mars, oppositions of Mars are not as frequent as the other outer planets and occur on average only once every 2 years and 2 months (780 days).
Unfortunately this time, Mars is close to aphelion and almost at its furthest possibly opposition distance from Earth. As a result, the planet will not be as bright or present such a large disk as compared to other times. But even so Mars still shines at magnitude -1.2, almost as bright as Sirius with an apparent diameter of nearly 14 arcseconds; which is large enough to observe the major surface details at high magnifications even through small telescopes. For comparison, at opposition in August 2003, Mars was less than 56 million km from the Earth with a magnitude of -2.9, brighter than Jupiter and an apparent diameter of nearly 25 arcseconds. This time closest approach to Earth occurs on March 5th when the two planets will be separated by 100.78 million km (0.674 AU).
During the month Mars continues its westerly retrograde motion in Leo moving ever closer to the star Regulus (mag. 1.35). At the end March, the two will be separated by about 6 degrees.
On March 8th the full Moon will pass 10 degrees south of Mars and 18 degrees to the SE of Regulus (6 UT).
Jupiter has been an impressive sight this apparition but is now disappearing fast into the twilight sky. The best time to view the giant planet is during the first half of the month when it will still be visible for up to 3 hours after sunset. As the month progress the planet sinks further towards the sunset horizon. Jupiter is still bright at magnitude -2.1, with a respectable apparent size of 35 arcseconds but March offers the last good chance to observer the planet before it reaches conjunction with the Sun in May.
On March 15th, mag -4.3 Venus passes 3 degrees north of Jupiter mag (11 UT).
Saturn is currently going from strength to strength in Virgo as it heads towards next month's opposition. The ringed planet is moving retrograde and now lies less than 7 degrees from first magnitude star Spica. Together with Mars in neighbouring Leo, both planets are now superbly placed for observation. At the start of the month Saturn rises less than four hours after sunset and by months end less than two.
On March 11th the Moon will pass 6 degrees south of Saturn, at the same time forming a nice triangle with Saturn and Spica (7 UT). During March the apparent diameter of Saturn is a respectable 18 arcseconds. The magnitude of Saturn changes minimally during the month, rising from 0.4 at the beginning to 0.3 at the end.
Uranus is in conjunction with the Sun on March 24th. However, there is a slim chance to catch the distant planet at the very start of the month when it is located in the evening sky just after sunset. A good time to try is on March 5th; Uranus is located only 2.5 degrees south of Mercury. At magnitude 5.9 it is a difficult binocular object in the dusk sky but possible to image alongside Mercury.
For the remainder of the month Uranus is unobservable.
After February's solar conjunction, Neptune is still to close to the Sun to be seen this month.
Solar System Data Table - March 2012
| ||Date||Right Ascension||Declination||Mag.||Size||Illum. (%)||Distance (AU)||Constellation|
|Sun||5th March 2012||23h 04m 04.7s||-05d 58m 42.8s||-26.8||32.3'||100||0.992||Aquarius|
|Sun||15th March 2012||23h 40m 55.9s||-02d 03m 47.0s||-26.8||32.2'||100||0.994||Pisces|
|Sun||25th March 2012||00h 17m 25.4s||+01d 53m 09.2s||-26.8||32.1'||100||0.997||Pisces|
|Mercury||5th March 2012||00h 08m 06.6s||+02d 43m 13.6s||-0.3||7.2"||48||0.932||Pisces|
|Mercury||15th March 2012||00h 17m 41.8s||+05d 41m 20.0s||2.3||9.8"||10||0.690||Pisces|
|Mercury||25th March 2012||23h 51m 01.2s||+01d 59m 42.4s||4.4||11.2"||2||0.600||Pisces|
|Venus||5th March 2012||01h 47m 51.8s||+12d 33m 28.1s||-4.2||19.0"||62||0.878||Aries|
|Venus||15th March 2012||02h 28m 58.0s||+16d 58m 07.7s||-4.3||20.8"||57||0.803||Aries|
|Venus||25th March 2012||03h 09m 41.8s||+20d 45m 44.8s||-4.4||23.0"||52||0.727||Aries|
|Mars||5th March 2012||11h 04m 32.6s||+10d 26m 34.1s||-1.2||13.9"||100||0.674||Leo|
|Mars||15th March 2012||10h 49m 53.0s||+11d 42m 06.6s||-1.1||13.7"||99||0.683||Leo|
|Mars||25th March 2012||10h 37m 36.2s||+12d 32m 59.9s||-0.9||13.1"||98||0.713||Leo|
|Jupiter||5th March 2012||02h 22m 53.3s||+13d 12m 03.2s||-2.2||35.7"||99||5.519||Aries|
|Jupiter||15th March 2012||02h 30m 26.5s||+13d 51m 06.0s||-2.1||34.9"||100||5.641||Aries|
|Jupiter||25th March 2012||02h 38m 33.5s||+14d 31m 26.2s||-2.0||34.3"||100||5.748||Aries|
|Saturn||5th March 2012||13h 51m 21.2s||-08d 34m 11.6s||0.4||18.5"||100||8.974||Virgo|
|Saturn||15th March 2012||13h 49m 29.3s||-08d 21m 42.2s||0.4||18.7"||100||8.870||Virgo|
|Saturn||25th March 2012||13h 47m 10.1s||-08d 07m 02.8s||0.3||18.9"||100||8.791||Virgo|
|Uranus||5th March 2012||00h 13m 34.3s||+00d 42m 55.6s||5.9||3.4"||100||20.986||Pisces|
|Uranus||15th March 2012||00h 15m 37.1s||+00d 56m 19.2s||5.9||3.3"||100||21.054||Pisces|
|Uranus||25th March 2012||00h 17m 42.5s||+01d 09m 55.6s||5.9||3.3"||100||21.066||Pisces|
|Neptune||5th March 2012||22h 13m 29.9s||-11d 35m 03.9s||8.0||2.2"||100||30.976||Aquarius|
|Neptune||15th March 2012||22h 14m 53.5s||-11d 27m 26.0s||8.0||2.2"||100||30.911||Aquarius|
|Neptune||25th March 2012||22h 16m 12.4s||-11d 20m 14.2s||8.0||2.2"||100||30.773||Aquarius|