April Night Skies
April Night Skies over Tanzania
Water, the elixir of life and the subject of intense investigations by astronomers looking for life in the Universe, is in the news. Traces of prehistoric water have been found in samples brought back to Earth from the Moon by astronauts of Apollo 15 spacecraft in 1971. The water is most likely to have come from prehistoric strikes by comets. Water has also been ‘seen’ beneath the surface in Mars’ equatorial regions which makes it an easy target of exploration by future Mars Rovers, thus making Mars possible to colonise.
Saturn commands the sky this month, visible as a sharp steady star in the east. It is on the move towards Regulus, the neck star in Leo constellation and is in retrograde (opposite) movement, going from east to west. Moon and all the planets normally move across the background stars from west to east but, for a short while, when the earth overtakes a planet in its orbital motion, the planet appears to move in the opposite (retrograde) manner due to parallax effect. The movement is quite marked and can be followed day by day. It is this forward and sometimes backward movement of planets which give them their name since ‘planet’ in Greek means ‘wanderer’. Saturn and Regulus will be closest together (only 2 degrees apart) at the end of the month. On 15th March the Moon will be close to this pair and will form an almost equilateral triangle with 2 degrees of separation on each side.
Mars, on the other hand also shows a remarkable (normal, west to east) movement away from the star Mebusta in Gemini after an almost contact meeting at the end of last month. The movement of Mars is also quite marked, similar to that of Saturn; hence by following how the two planets shift in relation to their nearby stars, you will be able to make out both the retrograde (opposite) as well as normal movements of planets during this month.
New Moon is on 6th April, and the crescent moon first comes close to within 8 degrees of the Pleiades star cluster (also called the ‘Seven little sisters’) on 8th. It will be almost half in the First Quarter phase and comes close to Mars to within 6 degrees on 12th. After its rendezvous with Saturn on 15th, the Moon will become Full on 20th.
Jupiter is still a late night planet, rising now soon after midnight. Mercury reaches a high altitude of 16 degrees by the end of the month making it possible to see in the western skies soon after sunset.
The prominent constellations of Orion, Taurus, Gemini and Sirius, which we have been following since the beginning of the year, are now crowded in the western sky and the Milky Way, which contains these constellations, stretches from northwest to southeast. The easily recognizable Orion constellation will bid us farewell as it fades in the brightness of the western sky at sunset.
Leo constellation takes its place, climbing high up in the eastern skies. This has a distinctive curve of stars that looks like a backward question mark which forms the head of the lion. Its brightest star Regulus, close to which Saturn appears this month, is in the neck of Leo. Regulus can also be identified as the dot in the question mark shape of Leo’s head. Regulus is a triple star, with two of them easily seen through a pair of binoculars. Virgo enters the sky, rising in the east, while late night, Scorpio pops its head over the eastern horizon.
The direction pointers, the Southern Cross and the Big Dipper (shaped like an inverted sauce pan) are up in the sky and are visible throughout the night. The long diagonal of the Southern Cross points towards the south while the edge of the pan in the Big Dipper points north.
The International Space Station (ISS) can be seen each day between 20th and 23rd April soon after sunset between 6:30 and 7:45 pm. For exact timings, check on the website www.heavens-above.com and, for Dar es Salaam, set the observing site at 6 degrees south and 39 degrees east.
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