Septmeber Night Skies over Tanzania
September Night Skies: A Cluster of Planets
By Dr. N. T. Jiwaji
ntjiwaji@yahoo.com
A compact clustering of planets just above the sunset line in the western horizon is the highlight of the month. The Moon is also the most sought after this month after being found just in time to begin fasting at the beginning of the month. It will also be in public attention again towards the end of September, most likely 30th, after the New Moon on 29th. This will usher in Idd celebrations perhaps on the first day of October.
The cluster is made up of Mars, Mercury, and Venus and Moon at the beginning of September. But the Moon quickly moves away leaving only the planets to linger together for the rest of the month. Though the setting sun can spoil the seeing, it is worth making the effort to see shade your eyes to see the shifting planets among the fixed stars. The whole play of the planets happens in Virgo (the Virgin) constellation, shifting from its bottom end to the upper part of Virgo by the end of the month. The cluster starts off within a couple of degrees (one finger-width at arm-length) apart, close to the horizon and inches up day by day. Venus comes very close to Mars (less than half a degree) on 11th September. By the end of the month the cluster is well separated and has shifted to the upper part of Virgo close to its brightest star Spica, which provides a useful stationary reference for gauging the shifts of the other planets around it. During the month brilliant Venus runs quickly away from the others going from below Mar to well above it. By the end of the month it will be well separated from the rest of the members of the cluster.
Jupiter lies in the overhead skies in Sagittarius. Though just as brilliant and with many more features through a telescope such as its four easily visible Galilean moons and its parallel belts of storm clouds, is not too prominent within the dense stars of the Milky Way. Its steady light marks it out within the twinkling stars around it.
Monday of 15th September should be a day to mark on your calendars if you want to watch astronomy coming alive. Together will all that this month’s sky has to offer, that day the International Space Station (ISS) will skirt the western horizon (blue path in sky map) around 7 pm. It will look like a slowly gliding star as bright as or brighter than Venus while the Full Moon will be rising in the East. The ISS comes close to Venus, which will allow us to compare their brightness. Confirm with a quick check on http://www.spaceweather.com/flybys/ or on more detailed http://www.heavens-above.com the exact timing of the ISS flyby. While there, look at all the other satellites that are visible in the early night skies. There are numerous such crafts though not as brilliant as the ISS but you can easily make a hobby of it.
The Milky Way stretches as a band of numerous stars across the middle of the evening sky, passing through the Southern Cross in the southwest, through Sagittarius overhead, to Cygnus in the northeast. Scorpio constellation can be clearly identified by its namesake, the scorpion, and can be seen high in the western sky. Locate its red “neck” star Antares which is a dying star in its red giant stage. The eastern sky has two “birds”; one to the northeast, where you will see the Cygnus with its body and wings making a wide cross, while in the southeast you will see the smaller bird Grus with its head twisted sideways. Try to become familiar with the brightest stars by their names and relative locations as seen in the map – Spica mentioned earlier locates the cluster of planets in the western horizon. To its right is brilliant Aructurs. Turning south you will see two stars upright, ready to pierce the horizon. These are none other than the pair Alpha- and Beta-Centauri, Alpha being the closest star to us after our Sun. At 4.2 light-years it is not too close, be sure (imagine 4 followed by 10 zeros kilometres) but that is the best we have. All the rest are farther away. Through a telescope Alpha Centauri is a doublet. Below the Alpa- and Beta-Centauri vertical is the Southern Cross which is lying sideways with its long diagonal parallel to the ground because the South Pole point in the sky towards which it points is in the sky, 6 degrees above the horizon. Facing north you will see the bright Deneb above which is the brilliant Altair. In the east is Formalhaut and to its right is rising Achernar. Paradoxically you will be able to make out these bright stars more easily from a light-polluted location like in the middle of the city rather than in the hinterland where hundreds of stars will clutter the view. So learn these bright stars and enjoy the skies with familiarity instead of confusion. Read recent stories on astronomy and space at http://universetoday.com and enjoy the night skies.
END