February Night Skies 2010

FEBRURARY 2010

Night Skies

Over TANZANIA

Though February is generally expected to be the most rain-free month of the year, the weather as it appears now may not live up to this expectation. Clouds come in when least expected but fortunately they often give way just in time to catch a glimpse of an interesting planet or star or nebula in the night skies. Hence let us see what the month has to offer so that we can enjoy the fruits of our perseverance.

The most remarkable sight in skies this February is that of the scintillating band of stars shining across the middle of the early evening skies from South to North. This is none other than the Milky Way, which is made up of a dense collection of stars and clouds of interstellar matter. The Milky Way is in fact our own galaxy of the same name, which is a flattened collection of about 100 billion stars, spread over a flat-disk shaped spiral 100,000 light year across, and 10,000 light years thick, rotating every 250 million years around a massive black hole. The narrow band of the Milky Way in our February skies is this huge system as we view it edge on. In fact all the visible stars that we see in our skies are part of our Milky Way galaxy.

Five of the top ten brightest stars can be recognized using the star map: The brightest of all stars is Sirius, followed by Canopus the second brightest star, which can be seen towards the south. The rest, in order, are: Rigel in ORION , Procyon to the east, Achernar will be setting in the southwest and Betelgeuse is a red giant star in ORION. After 10 p.m. they will be joined by Alpha-Centauri and Beta-Centauri, the bright stars rising vertically below the SOUTHERN CROSS.

The constellations that mark the band clearly are: ORION, GEMINI, TAURUS, and PERSEUS. A new addition this month is the FALSE CROSS, an asterism that has misled many a seafarer because it closely resembles the SOUTHERN CROSS, whose long diagonal points south. Locate the Southern Cross after 9 pm as it rises in the southeast, and by 8 pm near the end of the month. Since we are six degrees south, the long diagonal of the Southern Cross is first seen parallel to the horizon, since the south point is about six degrees from our location. As the night progresses, the long diagonal of the cross becomes more and more vertical, always pointing south as it rotates around the south point. LEO (the lion) pops its head above the eastern horizon at 8 p.m. and the whole Leo constellation should be easily recognizable by 9:30 p.m.

Of course all these brilliant stars in the Milky Way band can be best seen in dark skies away from the cities that cause the skies to brighten up due to light pollution from the lights on the ground that are unnecessarily pointing upward. Light pollution wastes precious energy and also hides from us the beauty of the scintillating night skies. From the city, the Milky Way is not as outstanding, but you will certainly see many more stars within the band than on either side. You will notice that towards the east or west the skies are distinctly devoid of stars.

One star which is not part of the Milky Way band, but which also shines brilliant red close to the band is the planet Mars. You can distinguish it from other stars by watching it carefully and see that it does not twinkle as do the other stars. Mars has just passed opposition (directly facing the sun) so it is shining brilliantly at the moment.

Mars is also in its retrograde (opposite) movement across the skies and will change over to normal motion by the middle of next month. Hence, it appears almost stationary, close to the heads of the Twins of Gemini, Castor and Pollux. All planets (and the Moon) shift their position regularly from west to east as seen against the stationary background of stars. However, when the Earth overtakes the planets, they appear to move in the opposite (retrograde) direction, that is, from east to west. Mars is retrograde at the moment and will resume its normal west to east movement from mid next month.

At around 9 pm, another planet enters the sky from the east – this is Saturn. Though it may seem to be twinkling when close to the horizon, it shines as a steady sharp point once it is half way up the sky. Through a telescope, its ring system is just starting to reappear after being lost for several months since the plane of the ring system was aligned exactly with our line of sight. This is the most beautiful planet to watch through a telescope, though its full glory of the view of ring system will only be revealed after some months.

The Moon will be close to the Pleiades star cluster (also known as Seven-little-sisters) on 21^st February, when it will be in quarter phase (half circle). This is the best time to see the Moon, since along the half-line the sun shines low on the Moon’s horizon and hence casts deep long shadows on the craters. At this time we can see the craters vividly deep and clear through a telescope or binoculars. The Pleiades are also beautiful to view through binoculars with the seven bright stars surrounded by shining nebulous clouds. A binocular scan of the Orion constellation in its sword region also shows the Orion Nebula as a bright cloudy patch.

The Moon is close to Mars on 25^th when it is close to its Full phase. It will be close to Saturn on 1^st March as the planet rises in the East with the Full moon just preceding it by half an hour.

The International Space Station (ISS) is visible on the 23^rd and 25^th February rising in the southwest on both days and shining brilliantly at magnitude -3.5. On the 23^rd it rises just after quarter to eight at 19:55 and sets and disappears when it is half way up the sky three minutes later. On the 25^th it rises just after 7 pm in the south east at 19:05 and crosses the whole sky and sets in the northwest seven minutes later at 19:12 passing close to Mars.

End