March 2013 Night Skies over Tanzania

home - Astronomy in Tanzania

March Night Skies over Tanzania

 

 

A recent story in social media which made newspaper headlines reported that two talented Tanzanian twins had returned to Tanzania after visiting Mars. Such exciting news spreads like wildfire because of people’s fascination with star, planets and outer space. However, the fact that such news is received without question is a cause for concern.

 

Up to now, Mars has been visited by spacecraft only and none of them have returned. There are very fundamental problems that are currently preventing humans from visiting even nearby planets. The first among them is energy. To carry fuel to reach Mars and have enough left for the return journey, spacecraft would have to be so huge that they would not be able to escape the Earth’s gravitational pull. Besides that, there is the biological challenge of surviving the nearly one year it takes to reach Mars. Add to that the psychological challenge of living in isolated confined space for such a long time. The best that has been able to be talked about at this stage is for a couple to visit Mars and establish a colony there, never to return!! Many other challenges exist including coping with conditions on Mars itself, such as lack of oxygen, extremes of temperature and many more.

 

Hence the story about the return of humans after visiting Mars should have been rejected outright. The fact that it was not, and was in fact circulated widely and believed by many, says millions about our state of knowledge. To be able to question things requires one to have a solid knowledge base. This can only be obtained through rigorous education. Our reaction to the Mars story tells us that we still have very far to go.

 

Another wake-up call was delivered by an unexpected meteor strike last month over Russia on February 15. The object was relatively small, about 20 metres wide and exploded about 20 kilometres above the Earth’s surface but damaged buildings and caused injury when it exploded over the town of Chelyabinsk. On the same day, another much bigger swimming pool size asteroid, called “2012 DA14” passed within the orbits of Earth satellites. This asteroid had been detected a few months earlier and its path calculated accurately enough to know that it would not hit Earth. There are several other asteroids that are known to have passed near Earth in the past month.

 

The last major asteroid that wiped out the dinosaurs was 65 million years ago when a mountain sized asteroid hit the Earth. However even smaller asteroids can cause significant damage such as wiping out a whole city. So the question at the moment is not “whether they will hit Earth”, but “when will one hit Earth”. Small asteroids are difficult to detect when they are sufficiently far away to give us enough warning about an impending disaster. Currently there is a determined effort from space agencies around the world to detect and locate in-coming asteroids that may be on collision course with our Earth.

 

While we are concerned about large space objects causing harm, we should understand that the earth is continually hit by thousands of small sand and dust particles.  When these strike the atmosphere, they heat up and burn out.  At night we see these as shooting stars.  At certain times of the year they are more frequent when the Earth passes through dust left behind by comets.

 

Among the objects from outer space that are currently visiting Earth is the comet Panstarrs. It has been in our southern skies since last week but the recent downpour obstructed us from viewing it near the western horizon just after sunset. Since we are near the equator, the comet is still above the horizon but further north. You will need to scan the bright horizon skies carefully, just below the crescent Moon, to catch a glimpse of this comet that has just rounded the Sun in its elongated orbit from deep space.  With the rainy season seemingly upon us a little early, we hope that our viewing will not be obstructed by clouds or rain. Follow further details on the progress of the comet on http://www.astronomyintanzania.or.tz

 

 

 

You will need binoculars to observe the wispy tail of the comet. The tail is formed when the Sun’s heat vaporizes the ice and dust that forms the comet. The extremely fine dust is pushed away by charged particles blown from the sun (called solar wind), and forms a long tail that always points away from the Sun.

 

Jupiter is the only planet that is visible half way up above the west horizon in the early night sky. It is close to the red giant star Aldebaran in “V” shape of the mouth of the bull (Taurus) constellation. Saturn rises after 10 pm in the East. The other visible planets, Mars, Mercury, Venus are all close to the position of the Sun so they are cannot be seen.

 

New Moon was on March 11 so this time is best for observing it through telescopes as it is in the crescent phase and will be most attractive when it is half phase called First Quarter on March 19 or soon after that when it has not reached Full Moon phase which will be on March 27. The Third Quarter is on April 3 when it is again in half phase but this is usually not seen by many because the Moon rises very late, after midnight.

 

The sky map shows the brightest stars Sirius and Canopus as five pointed stars. Other bright stars are shown as spots whose size depends on their brightness. The smallest black dots have a brightness of magnitude four. Fainter stars that can only be seen in rural environment where there are no major sources of light pollution are shown in the map as background dots. These are of magnitude 5 and 6. Stars of magnitude greater than 6 cannot be seen with the naked eyes and is the limit of human visibility. Notice that the magnitude scale is in reverse order with brightest stars having lower magnitude number while dim stars have high magnitude.

 

Due to light pollution in cities, municipalities and large towns, the faintest stars that we can see are of magnitude three or lower. When there is a Moon in the sky, even the magnitude 3 stars may not be seen easily. More exotic objects such as galaxies, nebulae, ‘dust’ bands, comets etc. are also blocked from our view. At best we can see not more than 300 of more than 1000 stars that should be visible at a time in the night sky. This shows how much of the natural beauty we are missing just because a huge amount of light is allowed to escape uselessly upward into the dusty air. We need to make just a small effort in awareness and dedication to arrest this growing problem before all the beauty of our urban skies is wiped out.

 

The Milky Way continues to dominate the overhead skies in the early night skies of March. It stretches from the Southern Cross in the southeast horizon, up through Sirius (the Dog), between Orion (the Hunter) and Gemini (the Twins) in the overhead skies, descending to Taurus (the Bull) and ending in Perseus in the northwest horizon. Leo (the Lion) fills the eastern sky while the pointers Southern Cross in the south and Big Dipper in the north rise early in the west and can be used to find north-south direction after 9 p.m. Be careful not to confuse the False Cross with the real one!

 

Moderate light pollution is useful for beginning astronomers since it is best to start observing the sky in cities on a night with moonlight. This will allow the beginner to start by first recognizing the positions of the brightest stars and then gradually continue observing during moonless nights and relate these with the known brightest stars. Finally, one can look for the fainter stars away from city lights and also observe star clusters and dust and gas clouds (nebulae).

 

March 20th is the day of Equinox when all over the world the length of day and night will be equal.

 

 

END

home - Astronomy in Tanzania

Comments