FEBRUARY 2013 NIGHT SKIES OVER TANZANIA
The world woke up on February 15 to a shocking asteroid strike in the skies over a small Russian town. The nearly 10 ton asteroid (OTHER ESTIMATES PUT IT AT 10,000 TONS, about the size a cube 20 meters on each side), caused much damage to property and injured hundreds by its shock wave due to its hypersonic speed of more than 100,000 kilometers per HOUR, which is 1,000 times the speed of sound. Such an extremely rare event was even more remarkable because of the coincidence of another extremely rare event. A much larger 50 ton asteroid 2012 D14 that had been accurately predicted to fly by close to Earth also passed us safely that night. The fact that two such remarkably rare events could happen the same day have some scientists scratching their heads. It is interesting to note that the two events are compared to what happens when we see shooting stars at night. Tiny grain of sand and dust continuously strike Earth as it sweeps space in its orbit around the Sun. The grains and dust burn up due to friction with the atmosphere. Such shooting stars delight us but are completely harmless, except that they increase the mass of our planet by a few tens of thousand tons each year due to the numerous strikes by extremely tiny dust particles.
We focus our attention this month on Jupiter, the extremely bright star that has been with us in the evening skies since December last year. It is seen close to a bright red star, Aldebaran. If you have been following its position, you might have noticed that the relative position of the Jupiter-Aldebaran pair has hardly changed. This is because it has been near the end of its retrograde (opposite) movement in the sky moving just slightly westward. However from this month onward it will regain its normal movement and by April it will have significantly moved on eastward. Such odd movements made the Greeks name them “planets”, which means “wanderers”.
With a reasonable telescope, you can focus your attention on the details of Jupiter. The giant planet has more than 100 moons but the four biggest ones, called the Galilean moons, can be seen using even a pair of 7 x 50 mm binoculars. However, to see the continuously changing positions of the moons around the planet, you will need a telescope that magnifies at least 100 times. Jupiter’s moons orbit the planet like a solar system of its own. (Did you know that Jupiter is so huge that if it had been just slightly larger it would have become a sun shining with its own energy, similar to our Sun).
Jupiter’s moons orbit the planet in a plane along which we are viewing them, so at times they go behind or come in front the planet. You can plan your viewing using the interactive observing tools on this website - http://www.skyandtelescope.com. With a 15 cm (6 inch) or larger telescope, you can enjoy the details of the surface of Jupiter, including its parallel belts of clouds and a giant storm system called the Great Red Spot. With even a large telescope you can notice the orange colour of Jupiter’s surface against the white bands of clouds. Ordinary telescopes show the planet in gray and white because there is not enough light entering your eye to stimulate your colour sensors. At night, or very distant hills in daytime also appear black and white due to limitations of our vision.
Among the other planets, Mercury will be at its brightest this month on February 21. You can catch sight of this elusive planet which hugs the west horizon at sunset due to its closest (and most rapid) orbit around the Sun. For late observers, Saturn enters the eastern sky after 11 pm. It will appear earlier and earlier and excite evening viewers for the next eight months. Venus is extremely bright in the early morning dawn skies, close to the east horizon. Full Moon will be on February 25. For more details visit www.astronomyintanzania.or.tz
The Milky Way cuts across the sky through the middle from south-south-east to north-north-west. The constellations that are within the path of the Milky Way are CANIS MAJOR with its brightest star Sirius, ORION with its numerous nebulae, TAURUS with its star clusters, the Hyades and the Plaeiades, PERSUS with it famous Andromaeda galaxy, and finally the W shaped CASSIOPEIA in the north. A new addition this month is the FALSE CROSS, an asterism that closely resembles the SOUTHERN CROSS but whose long diagonal does not point south. Locate it after 9 p.m. as it rises in the southeast. LEO (the lion) raises its head in the east at 8 p.m. and should be easily recognizable by 9:30 p.m.Five of the top ten brightest stars can be recognized using the star map: the brightest star is Sirius, followed by Canopus the second brightest star that can be seen towards the south. Rigel is in ORION , Procyon is to the east, Achernar will be setting in the west and Betelgeuse is in ORION. After 10 p.m. they will be joined by Alpha- and Beta-Centauri the brightest stars rising below the SOUTHERN CROSS.