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The Planets this Month - March 2013

Mercury

Although Mercury reaches inferior conjunction on March 4th, the planet rapidly moves out from the Sun so that only one week later it's visible as a morning object for observers in the tropics and southern hemisphere. The planet subsequently climbs higher in the sky and brightens each day until it reaches a peak altitude on March 31st, the date of greatest elongation west (28 degrees from the Sun). From northern temperate latitudes, the angle of the ecliptic is not favourable and consequently Mercury is unsuitably placed for observation this month.

As is often the case with Mercury apparitions, one hemisphere of the Earth is favoured over the other. On this occasion it's the turn of the southern hemisphere with the added bonus that this also happens to be the most favourable morning apparition of the year. With an extended period of visibility, the opportunity to spot the illusive planet is superb; Mercury is visible in the southern hemisphere morning skies for about 6 weeks from about March 11th.

From latitude 35S (approx. equal to Sydney, Cape Town and Santiago), Mercury will appear 4 degrees above the eastern horizon at 30 minutes before sunrise on March 11th. Since Mercury on this day shines at a dim magnitude 2.7, you will probably need binoculars to spot the planet against the bright twilight background. From then on glimpsing Mercury is much easier as it increases in brightness and climbs higher in the sky each subsequent morning. On March 16th, Mercury is now at magnitude 1.4 and 11 degrees above the horizon. The planets altitude continues to improve each day until March 31st when Mercury reaches maximum height, the date of greatest elongation west. On this date the planet is 20 degrees above the eastern horizon with a magnitude of 0.22, 30 minutes before sunrise.

It should be noted that once past greatest elongation west, Mercury continues to brighten as it begins to draw into the Sun. For this apparition, the planet does not reach maximum brightness (mag -1.0) until the very end of the visibility period, more than 4 weeks after greatest elongation west!

The diagram below shows the March and April morning apparition of Mercury from latitude of 35S.

Mercury morning apparition as seen from 35S, 30 minutes before sunrise

Venus

Venus passes through superior conjunction on March 28th. The planet is now located on the far side of the Sun and consequently unsuitably placed for observation throughout March.

Mars

Mars is now heading towards solar conjunction in April and is currently positioned close to the Sun. Consequently the "Red planet" is also unobservable this month.

Jupiter

Jupiter is now 3 months past opposition but despite fading in brightness the planet remains a brilliant object in Taurus. The gas giant is moving direct and positioned only 4.5 degrees north of magnitude 0.9 orange/red star Aldebaran and the famous "V" shaped Hyades open cluster. It's also just a few degrees east of M45, the famous Pleiades open cluster. With the planet now heading eastwards, Jupiter is gradually drifting away from this "Golden gate" section of the zodiac.

Jupiter is visible as soon as it's dark. At the end of the month, it sets just after midnight from northern temperate latitudes and a couple of hours before midnight for those living in the tropics and further south. The planets magnitude decreases from -2.3 to -2.1 during March with the apparent size diminishing from 39 to 36 arc seconds over the same time period.

On March 18th, the first quarter Moon passes 1.5 degrees south of Jupiter with the two objects forming a nice pairing.

Jupiter in Taurus during March 2013

Jupiter in Taurus during March 2013 - pdf format

Saturn

As Jupiter starts to fade from view, Saturn is becoming increasingly more prominent as it heads towards next months opposition. The "Ringed planet" is located amongst the faint stars of western Libra and is currently moving retrograde.

At the beginning of March, Saturn rises before midnight and a couple of hours earlier by months end. The planet brightens only slightly during March from magnitude 0.4 to 0.3. Likewise there is only a small increase in the apparent diameter of the planet disk (18 to 19 arc seconds).

Saturn's rings are currently wide open and a fantastic telescope sight. The ring tilt from our perspective is 19 degrees and even a small refractor telescope will easily show them. Larger telescopes display them in full glory, along with subtle details on the planet's surface and many of its brightest moons.

On March 2nd, the waning crescent Moon will pass 3 degrees south of Saturn.

Saturn in Libra in March 2013

Saturn in Libra in March 2013 - pdf format

Uranus

Uranus moves from Pisces into Cetus on March 4th. The planet then reaches solar conjunction on March 29th and hence is not visible this month.

Neptune

Neptune is currently located in Aquarius. The distant planet passed through solar conjunction last month and remains unsuitably placed for observation throughout March.

Solar System Data Table March 2013

 DateRight AscensionDeclinationMag.SizeIllum. (%)Distance from Earth (AU)Constellation
Sun5th Mar 201323h 02m 29.3s-06d 08m 37.7s-26.832.3'1000.992Aquarius
Sun15th Mar 201323h 39m 22.8s-02d 13m 49.8s-26.832.2'1000.995Pisces
Sun25th Mar 201300h 15m 51.8s01d 43m 01.7s-26.832.1'1000.997Pisces
Mercury5th Mar 201322h 53m 25.2s-03d 08m 05.5s5.510.7"010.627Pisces
Mercury15th Mar 201322h 27m 54.8s-07d 39m 50.7s1.610.1"170.663Aquarius
Mercury25th Mar 201322h 38m 25.5s-09d 05m 29.3s0.408.5"390.790Aquarius
Venus5th Mar 201322h 42m 27.5s-09d 41m 14.7s-3.909.8"991.707Aquarius
Venus15th Mar 201323h 28m 56.6s-04d 54m 57.4s-3.909.7"1001.717Aquarius
Venus25th Mar 201300h 14m 36.0s00d 04m 40.4s-4.009.7"1001.723Pisces
Mars5th Mar 201323h 39m 48.9s-03d 04m 22.0s1.204.0"1002.360Pisces
Mars15th Mar 201300h 08m 17.0s00d 06m 04.9s1.203.9"1002.378Pisces
Mars25th Mar 201300h 36m 33.3s03d 14m 39.6s1.203.9"1002.396Pisces
Jupiter5th Mar 201304h 25m 06.9s21d 10m 10.1s-2.338.7"995.099Taurus
Jupiter15th Mar 201304h 30m 04.6s21d 23m 03.5s-2.237.5"995.258Taurus
Jupiter25th Mar 201304h 36m 03.5s21d 37m 16.7s-2.236.4"995.410Taurus
Saturn5th Mar 201314h 38m 12.6s-12d 43m 26.9s0.418.0"1009.230Libra
Saturn15th Mar 201314h 36m 59.6s-12d 35m 31.5s0.418.3"1009.100Libra
Saturn25th Mar 201314h 35m 12.0s-12d 25m 09.0s0.318.5"1008.990Libra
Uranus5th Mar 201300h 26m 37.6s02d 08m 34.9s5.903.4"10020.966Pisces
Uranus15th Mar 201300h 28m 38.7s02d 21m 44.2s5.903.4"10021.021Cetus
Uranus25th Mar 201300h 30m 43.5s02d 35m 12.7s5.903.3"10021.048Cetus
Neptune5th Mar 201322h 21m 00.2s-10d 56m 39.7s8.002.2"10030.961Aquarius
Neptune15th Mar 201322h 22m 24.1s-10d 48m 49.8s8.002.2"10030.915Aquarius
Neptune25th Mar 201322h 23m 43.8s-10d 41m 24.8s8.002.2"10030.843Aquarius

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