July Night Skies and First Crescent Visibility over Tanzania
The holy month of Ramadhan is ready to grace us in a few days, and with it, people’s attention will turn skywards to look for the first crescent Moon. It affects everyone, not Muslims only, since the sighting of the New Moon marks the end of Ramadhan and brings with it a joyous holiday. However, besides the clockwork timing of the events in the heavens, other factors filter in to complicate the job of sighting the first crescent Moon. For astronomers, this is a blessing since the mysterious working of the heavens will amaze people sufficiently to attract a fresh batch of budding astronomers.
The astronomical new Moon is on Monday July 8 at 10:14 am Tanzanian time. At this instant, the Moon’s longitude (right ascension) is exactly aligned with the Sun so the dark face of the Moon is exactly facing us, making it impossible to see. We have to wait until sunset to find out whether the first crescent will be sufficiently seen the Moon shifts towards our night ward side (i.e. eastwards) as time progresses. However, by sunset of July 8, the shift of the Moon will be just a little more than two degrees so it will be too close to the glare of the Sun to be seen from anywhere on earth, except a small part of Polynesia.
We will have to wait for it to shift sufficiently away from the Sun over the next 24 hours for a chance to see the first crescent. By this time, on July 9, the moon will have had time to shift by 11 more degrees making it 13 degrees away from the Sun. During this 24-hour period, the crescent will have also increased significantly in size and brightness against a darker the sky as the Sun dips further below the horizon. (You can visualize how the crescent shape arises because the Sun shines on the Moon from below even when the Sun has set below the western horizon).
The high position (elevation) above the horizon and a greater brightness of the crescent on 9th July will make it clearly visible to everyone (clouds not withstanding). This sighting can allow the announcement to be made for the beginning of Ramadhan the following day, on July 10. The same process will repeat itself during the Moon’s next cycle, and it will be of more interest for all Tanzanian since it will usher in the Idd holidays. We will follow up on dates and progress of the Moon in our next month’s article or you can follow the progress of the Moon on our website www.astronomyintanzania.or.tz .
Besides the Moon, there is an extremely brilliant planet has captured the western sky. This is none other than shiny Venus. It is currently at an elevation of more than 20 degrees above the western horizon and continues to rise as days go by. It will dominate the skies for the next five months to reach its peak height and brightness in December after which it will slide back down by the end of the year. On July 10, a crescent Moon will be closest to Venus approaching it to within 10 degrees.
Another planet in the night skies at this time is Saturn. It can be seen in the overhead skies in the evening shining with a piercing steady light quite different from the twinkling stars nearby. This ringed planet presents the most beautiful sight in a telescope. On July 16, the Moon will be placed very close to Saturn within 3 degrees from the planet.
Among the brightest stars noticeable in the July skies are: Alpha and Beta Centauri in the south form the pair that points continuously towards the Southern Cross; the fourth brightest star Arcturus is overhead towards the north, and the fifth brightest star Vega rises in the northeast. Other bright stars you will easily notice are Altair, which rises in the east and Spica, the brightest star in the Virgo constellation can be seen almost overhead towards the west.
Among the constellations, the north and south direction pointers (Big Dipper and the Southern Cross) are high enough in the evening skies to help you mark north south directions. Scorpius with a shape matching a scorpion, is the dominant constellation this month, occupying the overhead evening sky with its three stars forming its tentacles, the red star Antares in its neck, and a long winding tail that ends in a close pair forming the sting. Below Scorpius, try to identify Sagittarius (the archer). This constellation marks the direction of the centre of our Milky Way galaxy with a noticeably high concentration of stars and nebulae. The Milky Way band passes through the Southern Cross, Sagittarius into Cygnus (the swan) in the northeast.
The International Space Station (ISS), shining as bright as Venus, can be seen on Saturday July 6 moving majestically from northwest at 7:05 pm hugging the southwest horizon rising to a maximum elevation of 23 degrees, after which it will continue southeastwards where it will disappear at 7:12 pm. To view more satellites enter your location in www.heavens-above.com.