november2008nightskiesovertanzania
November 2008 Night Skies over Tanzania
NIGHT SKIES OVER TANZANIA
NOVEMBER 2008
By Dr N T Jiwaji
ntjiwaji at yahoo dot com
The focus of our attention this month are the two brightest jewels in the sky: Venus and Jupiter. Venus is closer to the horizon in the west while Jupiter is higher in the same direction closer to zenith at sunset. Both are in the constellation of Sagittarius; Venus below it and Jupiter above it. The two show very distinct movement as they approach each other over the course of the month and finally meeting together at the end of the month.
The closest approach is on 30th November separated by about two degrees (about 3 finger-widths). The day after, that is on 1st December the two bright planets together with the crescent moon pose a show of a lifetime. The moon will come in between Venus and Jupiter. The more interesting thing to watch is the shift of the moon relative to the two planets. Soon after sunset, it will be below the pair forming an approximate right angled triangle. But over the course of a few hours it will shift its position as the triangle is squeezed slowly as the crescent moon come in between the two planets to form a straight line by 8:30 pm. The trio will be close to the horizon by that time so you will need to find a clear vantage point with a clean view of the western horizon as they set soon after 9 pm.
Through a telescope, Jupiter’s four moons can be seen as pinpoints in a straight line. The number of moons visible change as they revolve around the planet. These two facts show that the moons are orbiting Jupiter in a flat plane, similar to how the planets themselves orbit the sun.
Venus shows up as a oblong shape in a telescope since part of its face is on Venus’s night side. As the months go by Venus’s shape through a telescope will change dramatically as it approaches Earth in its orbit around the sun. The shape will change to half phase with half the side on the daylight side and half in the night side.
From then on until the beginning of March next year Venus will become dramatic in its shape and size when viewed through a telescope, as it changes to a crescent shape that becomes larger as the planet approaches closest to Earth by 10th March next year. Over this period, Venus’s brightness remains almost the same since the decrease in its lighted area visible to us is compensated by its increasing apparent size.
This month we will also witness the Leonid meteor shower, famous for the meteor storms associated with it, which last occurred in 2001 and occur every 33 years. The meteors will appear to be coming from the eastern sky radiating from Leo constellation ( hence the name ‘Leonid’). It will peak on night of 17th November and will be visible from about 2 a.m. (of i.e. 18th ). There will be an increase in meteor activity a few days around 17th but the peak of 18th /19th is expected to last only a couple of hours. The Moon will be near its last quarter phase so a half moon will be in the sky. So its brightness can reduce a little the number of meteors seen. You can expect to see about 10 meteors per hour.
The Andromeda galaxy can still be seen close to the Square of Pegasus nearer to the northern horizon while the SMC lies similarly between Achernar and the South. To the naked eyes in relatively dark skies, both galaxies appear as fuzzy patches about 4 degrees across.
The bright stars worth knowing by name this month are: Fomalhaut, Altaír, Deneb in Cygnus (the northern bird), Vega, Achenar and Aldebaran, in constellation Taurus just rising in the east. These are all first magnitude stars. Second magnitude stars are shown in white letters. They are: X = Al Nair in Constellation Grus (the bird), Y = Peacock, Z = Kaus Australis in the Sagittarius constellation. The large easily recognizable rectangle of the Orion constellation with three close by stars in its mid diagonal now rises soon after 9 pm preceded by the Pleiades cluster of stars (also known as seven little sister) and the red star Aldebaran in Taurus (the bull) constellation. Orion (the hunter) is followed by the brightest star in the sky Sirius (in the Canis Major, the dog, constellation). You can remember this by imagining Orion the hunter is hunting Taurus the bull followed by his faithful dog.
The variable star Algol in Perseus is a special star because it varies quickly in brightness approximately every three
days (actually 2.87 days, i.e. 2 days, 20 hours and 48 minutes). It is one of the oldest known variable stars since its
discovery in 1669 by Geminiano Montanari. It varies in brightness from a maximum magnitude of 2.1 to its lowest, but
still visible magnitude of 3.4. So it is possible to follow its changes in just a few days. This month the minima occur on
14th at 00:45 after midnight and on 17th at 09:34 pm. So the most convenient date is 17th because it will reach a
minimum in the early part of the night. You should locate the star by Saturdy 15th November so that you can follow it for
the next three nights and notice a decrease in brightness until it reaches a minimum on 17th and then for another two or three
nights while it becomes brighter. Locate it on the north eastern skies using the sky map. Keep in mind the brightness of
nearby stars so that you can compare their constant brightness with the changes in Algol’s brightness.
The Milky Way band across the sky winds its way from south west to north east, straddling the
western horizon so it does not cross the sky. Hence this month most of the sky will appear to have rather few stars
because it is well away from the bright band.
From 10th to 13th November, the International Space Station (ISS) will be seen brightly in the evening skies within an hour after sunset. The best views will be on 11th and 13th when it will cut across the whole sky rising from south west and disappearing in the north east horizon. On 11th it rises at 7:15 pm, rises up into the sky, with highest point reached at 7:20 pm and goes down into the north east, setting below the horizon at 7:22 pm. On 13th it passes between the two bright planets Venus and Jupiter. But it is in the sky while the sky is still a bit bright immediately after sunset so you will need to go out early to mark it. It rises at 6:30 pm again in the south west and sets at 6:40 into the north west horizon.
End