Mercury starts March about halfway through an extended morning visibility period for observers at equatorial and southern latitudes. On February 24th, the fast moving planet reached greatest elongation west and was at highest altitude for this apparition. For example, from latitude 35S (approx. equal to Sydney, Cape Town and Santiago) Mercury was easily visible at magnitude 0.0, hovering 16 degrees above the eastern horizon, 45 minutes before sunrise.
During March, its altitude decreases each subsequent morning but the planet remains visible until lost to the bright twilight glare a few days before months end. However, it should be noted that Mercury doesn't reach maximum brightness (mag -0.7) until the very end of the visibility period, more than 4 weeks after greatest elongation west!
On March 6th, Mercury reaches aphelion - the point in its orbit where it's farthest from the Sun - and is located 0.467 AU (approx. 69.9 million kilometres or 43.4 million miles) from our star. Later in the month on March 17th, the planet passes 1.6 degrees south of much fainter Neptune (mag. +8.0). The difference in brightness between the two planets is about 1,500 times. Two days later, the thin waning crescent Moon passes 5 degrees north of Mercury.
Unfortunately, from northern temperate latitudes the angle of the ecliptic is not favourable and the planet always remains very low down and unsuitably placed for observation throughout the month.
Venus, mag. -4.0, is now a brilliant evening object visible towards the west after sunset. From Northern Hemisphere latitudes the planet sets almost 3 hours after the Sun at the start of the month, increasing to nearly 3.5 hours by months end. The visibility period from southern latitudes is not so favourable but Venus can still be seen for about 1.5 hours. Despite this the planet is unmistakable, a dazzling beacon of light illuminated the early evening skies.
The closest planet-planet conjunction of 2015 occurs on March 4th when Venus at 20 UT passes just 0.1 degrees north of much fainter Uranus (mag. +5.9). Use binoculars or a small scope to spot Uranus, which is 10 magnitudes or 10,000 times fainter than Venus. Also visible five degrees southwest of the pair is Mars (mag. +1.3).
Later in the month on March 22nd, the waxing crescent Moon passes 3 degrees south of Venus making a lovely evening pairing.
Mars continues its direct motion spending most of the month in Pisces although it does make a small cut through one corner of Cetus on March 2nd. The "Red planet" exits Pisces on March 30th, moving into neighbouring Aries.
Throughout March, Mars appears as an inconspicuous early evening object visible above the western horizon as soon as it's dark enough. At the start of the month the planet's located 4 degrees southwest of brilliant Venus. By months end Venus has distanced itself to 17 degrees. To the naked eye, Mars (mag. +1.3) resembles a first magnitude star that sets about 2 hours after the Sun from northern temperate latitudes but only 1 hour for those located further south.
On March 11th, Mars passes just 0.3 degrees north of Uranus with at least binoculars required to spot Uranus. Telescopes at medium to high magnifications reveal the disks of the two planets, Mars at 4.1" across appears slightly larger then Uranus (3.4").
On March 21st, the waxing crescent Moon passes 1 degree south of Mars.
While Venus is the brilliant "star" above the western horizon for a short time after sunset the planet that reigns for the rest of the night is Jupiter. The giant planet is now just one month past opposition and a stunning object moving slowly retrograde amongst the faint stars of Cancer. The current declination of Jupiter slightly favours Northern Hemisphere observers, but even from Southern Hemisphere latitudes where the planet appears lower down, it's unmistakable due to its brightness.
Jupiter is visible towards the east as soon as it's dark enough and remains so until the early hours of the morning. It starts March at magnitude -2.5 with an apparent diameter 45 arc seconds. By months end its slightly fainter and smaller at magnitude -2.3 and 42 arc seconds respectively. Even when viewed through a small telescope a wealth of surface details are visible including cloud bands, twists, knots and storms; including the most famous of all "The Great Red Spot". Also easily visible, but not always at the same time are the four bright Galilean moons: Io, Europa, Ganymede and Callisto.
On March 3rd and 30th, the waxing gibbous Moon passes just over 5 degrees south of Jupiter.
Saturn is located in Scorpius and on March 14th reaches the first of its two stationary points for 2015. This date signals the change in the planets motion from direct to retrograde and is also widely regarded as the beginning of this year's opposition period. By the end of March, Saturn rises before midnight for observers at northern temperate latitudes but nearly 3 hours earlier for those located further south.
As the month progresses the planet brightens slowly from magnitude +0.5 to +0.3 with its apparent size marginally increasing from 17 to 18 arc seconds. Saturn is easy to find in the northern section of Milky Way rich Scorpius. The only nearby star of similar brightness is supergiant star Antares (α Sco mag. +1.0). Visually the two cannot be mistaken, slightly brighter Saturn appears white in colour compared to the stark deep red hue of Antares (a few degrees to the southeast).
Of course the rings of Saturn are its most famous feature and even a small telescope will show them. Through medium and large aperture scopes they are a fantastic breathtaking sight. In addition to the rings a handful of Saturn's moons are also visible. The largest and brightest Titan shines at eight magnitude and can be seen with binoculars. In addition, small size scopes will also show other moons including Rhea, Tethys and Dione.
At the beginning of the month a good opportunity exists to spot bizarre moon Iapetus. This world is famous for its "two-tone" colouration with one side being much darker in colour than the other. As a result, Iapetus when positioned on the western side of Saturn (when viewed from Earth) appears brighter than from the opposite side. On March 3rd, Iapetus reaches greatest western elongation and therefore at it's brightest. At magnitude +10.1, it can be seen with a small scope of 80mm (3.1-inch) aperture.
The 65% illuminated waning gibbous Moon passes 2 degrees north of Saturn on March 12th.
The first half of March offers the last opportunity to view Uranus before it's lost to the bright evening twilight sky. The first planet to be discovered in the telescope age is located in Pisces and starts the month setting about 3 hours after the Sun from northern latitudes but much less from further south. Although technically visible to the naked eye at magnitude +5.9, optical aid will be required to spot Uranus as it battles low down against the twilight sky.
An interesting conjunction occurs on March 4th when brilliant Venus (mag. -3.9) passes just 0.1 degrees north of Uranus. Although 10,000x brighter than Uranus it should be possible to spot the distant planet with a binoculars or a small scope. A second close planetary conjunction occurs a week later on March 11th when Mars passes 0.3 degrees north of Uranus.
Neptune reached solar conjunction on February 26th. The planet is currently located in Aquarius and remains unsuitably placed for observation throughout March from northern temperate latitudes. However, during the second part of the month observers located at tropical and southern latitudes should be able to locate the planet low down above the eastern horizon just before sunrise. At magnitude +8.0, optical aid is recommended to glimpse the planet.
On March 17th, Mercury passes 1.6 degrees south of Neptune. At magnitude -0.3, Mercury is easily visible to the naked eye and over 1,500x brighter than much more distant Neptune. The thin waning crescent Moon passes 4 degrees north of Neptune on March 19th.
Solar System Data Table March 2015
|Date||Right Ascension||Declination||Apparent Magnitude||Apparent Size||Illum. (%)||Distance from Earth (AU)||Constellation|
|Sun||5th Mar 2015||23h 00m 35.2s||-06d 20m 29.7s||-26.8||32.3'||100||0.992||Aquarius|
|Sun||15th Mar 2015||23h 37m 29.5s||-02d 26m 02.4s||-26.8||32.2'||100||0.994||Pisces|
|Sun||25th Mar 2015||00h 14m 00.3s||01d 30m 58.0s||-26.8||32.1'||100||0.997||Pisces|
|Mercury||5th Mar 2015||21h 25m 02.6s||-16d 28m 09.6s||-0.1||06.2"||70||1.084||Capricornus|
|Mercury||15th Mar 2015||22h 21m 10.9s||-12d 30m 43.8s||-0.2||05.6"||80||1.204||Aquarius|
|Mercury||25th Mar 2015||23h 22m 34.0s||-06d 29m 26.6s||-0.6||05.2"||89||1.295||Aquarius|
|Venus||5th Mar 2015||00h 54m 58.8s||05d 18m 22.0s||-3.9||12.2"||86||1.364||Pisces|
|Venus||15th Mar 2015||01h 39m 44.1s||10d 19m 12.5s||-3.9||12.7"||83||1.310||Pisces|
|Venus||25th Mar 2015||02h 25m 22.6s||14d 56m 44.2s||-4.0||13.3"||80||1.251||Aries|
|Mars||5th Mar 2015||00h 36m 29.0s||03d 27m 06.2s||1.3||04.2"||98||2.252||Pisces|
|Mars||15th Mar 2015||01h 04m 20.4s||06d 29m 57.6s||1.3||04.1"||98||2.294||Pisces|
|Mars||25th Mar 2015||01h 32m 16.4s||09d 25m 05.4s||1.4||04.0"||98||2.335||Pisces|
|Jupiter||5th Mar 2015||09h 07m 54.7s||17d 30m 20.8s||-2.5||44.2"||100||4.456||Cancer|
|Jupiter||15th Mar 2015||09h 04m 20.4s||17d 45m 32.4s||-2.4||43.3"||100||4.549||Cancer|
|Jupiter||25th Mar 2015||09h 01m 52.0s||17d 55m 32.5s||-2.4||42.3"||99||4.664||Cancer|
|Saturn||5th Mar 2015||16h 12m 18.3s||-19d 01m 45.1s||0.4||17.0"||100||9.758||Scorpius|
|Saturn||15th Mar 2015||16h 12m 38.7s||-19d 00m 58.8s||0.4||17.3"||100||9.597||Scorpius|
|Saturn||25th Mar 2015||16h 12m 17.0s||-18d 58m 27.6s||0.3||17.6"||100||9.445||Scorpius|
|Uranus||5th Mar 2015||00h 54m 11.2s||05d 07m 01.3s||5.9||03.4"||100||20.849||Pisces|
|Uranus||15th Mar 2015||00h 56m 08.0s||05d 19m 24.3s||5.9||03.4"||100||20.925||Pisces|
|Uranus||25th Mar 2015||00h 58m 10.9s||05d 32m 19.8s||5.9||03.4"||100||20.975||Pisces|
|Neptune||5th Mar 2015||22h 37m 10.5s||-09d 30m 17.3s||8.0||02.2"||100||30.952||Aquarius|
|Neptune||15th Mar 2015||22h 38m 35.0s||-09d 22m 04.7s||8.0||02.2"||100||30.920||Aquarius|
|Neptune||25th Mar 2015||22h 39m 56.3s||-09d 14m 12.3s||8.0||02.2"||100||30.861||Aquarius|