The Southern Hemisphere Sky This Month

by Mark Armstrong

February 2012

Darkness falls around 9pm EDT in mid February and the familiar form of Orion the Hunter dominates the view to the north, with the three bright stars forming his belt right on the meridian at a healthy 57 degrees. Extend the line of the stars north-westwards to find the V shaped group of stars called the Hyades star cluster, the main pattern to identify Taurus the Bull and dominated by the red giant Aldebaran, a first magnitude beacon that is actually not a member of the Hyades. Some twenty degrees south-east from Orion's belt lies blazing Sirius, at mag. -1.4 by someway the brightest star in the entire sky. The fine open cluster M41 lies a mere four degrees south of Sirius.

Looking to the south will quickly locate mighty Canopus, the luminary of the magnificent constellation of Carina, the Keel (of Argo Navis), the second brightest star at mag. -0.62. Canopus is just about to culminate and appears to drag the rest of Carina along as it rises in the south-south east. Following in Carina's wake are the great constellations of Crux and Centaurus, with its famous pointer stars Alpha Centauri and Hadar (beta) a mere 12 degrees up but will be well on show by midnight.

The major planets are well represented this month with Mars and Saturn leading the way. Mars is only a month away from opposition and there is a tangible growing excitement within the astronomy community. At the start of February the red planet shines at magnitude -0.54 and it is an unmistakeable object shortly after midnight on the Virgo/Leo border above the north-eastern horizon. Through a telescope it shows an almost fully illuminated disc (96 percent) spanning 11.8 arcseconds across, only two arcseconds shy of what it will be at opposition. Mars is not an easy planet to observe as all too often it shows a disappointingly small disc at the eyepiece. A small telescope will show the polar brightening and the major dark marking but at least a 150-200-mm 'scope is recommended to see much in the way of surface detail.

The most obvious and familiar surface feature on Mars is the wedge or 'V' shaped Syrtis Major. In the first week of February it lies on Mars' preceding eastern limb at 12.30 am and quickly disappears due to Mars' west to east rotation. By the 10th at midnight it can be found right on the Martian central meridian (CM 280°) and is visible for about four hours. Mars appears to retro-revolve with an illusory east to west rotation and this causes the same surface feature to face us 37minutes later each night. So by the 20th the Syrtis Major will rotate into view on the following western limb by 1.30 am but take until 5am to transit the CM. At the end of February it will not be visible during the hours of darkness. By this time Mars will have brightened substantially to mag. -1.2 and grown to 13.8 arcseconds in apparent diameter. It will be above 20 degrees in an astronomically dark sky from 9.45pm EDT until about 5.30am, culminating at 1.30am among the stars of Leo at 46° altitude.

Saturn is a post midnight object close to Spica in Virgo, attaining an altitude of 20° by 1.15am EDT. By the end of February it transits at 4.20am. Through even a small telescope Saturn is an unforgettable sight with the rings, now some 15° open, well seen. Saturn's peculiar moon Iapetus reaches greatest western elongation on 8 February, when it is two magnitudes brighter (mag. +10.2) than at eastern elongation; an easy target for a 100-mm refractor.

Venus is a blazing evening star setting about 2 hours after the Sun and on the 10th is within half a degree of Uranus. Jupiter is still an impressive object in the north-western evening sky as darkness fall but it starts to battle against the twilight glow by the end of the month. On the evenings of 25-27 February, the crescent moon joins Jupiter and Venus to give some great views and photo opportunities.