June 2009 Night Skies Over Tanzania
A regular occurrence around this time of the year is the Moon-Mars hoax that you may receive as an email forwarded by friends. Such emails that fly around the world describe a supposedly closest approach in August of our nearest neighbour Mars, which would make it rival the Moon and you would see two moons on the night of August 27th. However, do not be fooled because firstly, the closest approach of Mars took place in 2003, and though the planet was seen at that time as a brilliant red star, it never was and in fact can never appear as large as the Moon. Such emails are forwarded by people who, though amazed by astronomy, are not bothered to understand the mysteries of how our Universe works.
Let us look at the facts. Mars came closest to the earth in nearly 60,000 years on August 27th 2003. Even then it was still nearly 55 million kilometers away from us. Though Mars is nearly the size of earth, an object that far away can only appear as a tiny point from earth using only our naked eyes. Though Mars is the next planet after the earth as they orbit the sun, Mars can also reach five times farther away from earth - nearly 300 million kilometers from earth at its farthest point. Hence we usually see Mars as an inconspicuous red point in the sky. However since during its closest approach in 2003 it came five times closer, it became 25 times brighter because of the inverse square law that applies as the light from the planet is spreads out over a much smaller sphere (i.e. 25 times smaller surface area).
When a star or a planet is very bright, it appears as a big spot rather than a point because the starlight is spread out in a cone as it passes through our atmosphere. Without this envelope of air around us, all stars and planets would appear as pinpoints in an absolutely dark sky (even during the day!!). But it can never be seen as big as the Moon!! The idea that Mars would look so big came after comparing pictures of the full Moon with those of Mars taken through a telescope showing details of its features, including its ice caps, which cannot be seen easily when Mars is much farther away.
Hence do not be fooled by an email that you may receive that tells you about this amazing event. And if you are an amateur astronomer you will have an even harder time explaining yourself if you have a gathered a group of family and friends on 27th August to witness the so called extraordinary event. During the current rotation of Mars and earth they will come close only in January 2010.
Let us now turn our attention to the reality of what is happening in our night skies this month. Mars is seen in the dawn sky before sunrise in the east as a tiny red point in the eastern sky. It is also close to a much brighter Venus and the pair will come closest on 21st June, which is also the northern solstice day.
Saturn is high in the western sky in the early evening soon after sunset. It lies at the foot of Leo the Lion constellation. A crescent moon will come close to Saturn on 27th June after the New Moon on 23rd June. Since Saturn is now very close to its “ring plane crossing”, which will occur on 4th September 2009, it will be hard to see its rings since we will be viewing the ring along its plane. This situation will last for several months so we will miss this beautiful sight of Saturn’s rings for a few months. However we should still be able to see some bands on the planet and of course we will continue to see a few of its moons as star-like points in a line along its diameter.
Jupiter rises in the east by 10:45 pm so it is still possible to arrange an evening during a weekend to observe this planet as a bright star rising majestically to dominate our evening skies for several months. Through a telescope it is the most interesting planet to observe now. You will see parallel bands crossing its disk, which are actually huge cloud systems. You might also see the Giant Red Spot which is a huge tornado raging on Jupiter. Its four major moons which were first seen by Galileo through a simple telescope 400 years ago can be seen lined up on either side of the planet along its diameter. When watched over a period of time, even over a few hours, you will see the moons as star-like points shifting their positions as they revolve around the planet.
The sky map shows us that we can see nearly 18 constellations and asterisms in the night skies this month. Marked alphabetically from A to R these are, from south to north, then east to west: A – Sagittarius the archer, B – Scorpius, C – Ara the alter, D – Triangulum Australe, the southern triangle, and E – the famous Southern Cross continuously pointing south. F – is the False Cross, G – is Vela, the sail, H – is the zodiacal constellation of Libra the scales of justice and I – is the long Hydra the snake. J is Virgo the virgin while K – is Leo the Lion. L - is Cancer the crab while M – is Hercules, N – is Bootes the herdsman and O – is the famous Big Dipper pointing north. P – is Ursa Major, the big bear while Q – is Draco the dragon. R – is the Little Dipper in Ursa Minor whose end star is the North Star but which we never see as it is below the horizon.
Among the bright stars marked ‘m’ to ‘s’ on the map are: ‘m’ – Alpha Centauri the closest star at a distance of 4.3 light years and ‘n’ – is Beta Centauri. ‘o’ - is red star Antares in the neck of Scorpius, ‘p’ – is Spica in Virgo while ‘q’ is the third brightest star Aructurus (the first and second brightest stars are respectively Sirius and Canopus will have set in the south west by 8 pm). ‘r’ – is Regulus in Leo while ‘s’ – is Procyon.
The full glory of the dense concentration of stars and dust can be seen in the Milky Way which stretches across the southern skies from southwest to southeast containing the constellations or asterisms C, D, E, F and G. It runs parallel to the zodiacal constellations A, B, H, J, K, L.
June 21st is the Solstice, when the Sun starts its journey back towards the Equator after completing its journey north to the Tropic of Cancer. This day marks the beginning of northern summers and southern winters.
The International Space Station (ISS) will next be seen as a very bright and prominent spot in the evening skies on 4th and 6th July. On 4th July, prepare yourself well before 7:30 and orient yourself to observe the ISS rising from the south west. It will rise high upto and will reach almost overhead in about 3 minutes and will disappear abruptly from view as the sunlight hitting it from below will be cut off when it enters that earth’s shadow. On 6th July it will also rise in the south west but at about 6:40. This time it will rise high in the sky and drop back in the north east and sets below the horizon after about 5 minutes. The ISS has been built bit by bit with units added by various nations over the past 11 years to make a huge facility the size of a football field. It orbits the earth at a height of 350 kilometers above earth. A few more units remain to be added. A very interesting timeline of its assembly in space high above the earth can be seen at: http://i.usatoday.net/tech/graphics/iss_timeline/flash.htm
END