ASTRONOMY EVENTS OF THE YEAR AHEAD
Among the astronomical events that await us is the solar eclipse on November 3 that will cut off about 70 percent in Tanzania, but the total darkness will also occur, and close to us, in a path that passes through northern Uganda and Kenya. This year we may witness the appearance, at the end of November, of possibly the brightest comet of all time.
Other major events that await us are a deep penumbral lunar eclipse on April 25 which will dull the bright Full Moon that night. This is also the year of maximum sunspots, which has come after several years of deep minimum with no sunspots seen for nearly a year.
The planetary dances of Jupiter, Venus, Saturn and Mercury and Moon will sparkle your nights as they shift positions in the east-west skies meeting up once in a while and forming attractive pairs and groups.
The Globe at night campaign for measuring light pollution over your own night skies light will be conducted several times during the year.
The November 3 Total Solar Eclipse path will begin at 01:04 pm over the Atlantic Ocean, moving into the West African forests into Gabon, then into northern Uganda and Kenya where the duration of totality will be a few seconds. The total eclipse ends in southern Ethiopia at 06:29 pm. The best viewing place will be near Lake Turkana in Kenya where the eclipse will be total at 05:25 pm with totality lasting only 14 seconds.
In Tanzania we will experience a Partial Solar Eclipse with a maximum of 70 percent of the Sun covered up. It will last from 4:24 pm until sunset, with maximum of 70 percent of the Sun covered at 05:28 pm after which it will clear and the eclipse will end after sunset in Dar es Salaam. Observers in the west of the country, beyond Dodoma, Mbeya and Mwanza will see the end of the eclipse just before the Sun sets at their locations. Another solar eclipse that will take place this year is a fully annular eclipse on 10th May 2013. However, it will not be seen in Tanzania since it will occur on the other side of the world.
Three Lunar eclipses also occur, th all three of them being penumbral lunar eclipses. The most remarkable of these will be the first one on April 25, 2013 centred over the Indian Ocean. It is a deep penumbral eclipse with a grazing partial phase where a very small part of the north edge of the Moon will be darkened by the Earth’s shadow. A penumbra is a light shadow that you see around the edge of a dark shadow. At large distances, this faint penumbra occupies a large area hence the whole Moon can sink inside the faint shadow. This is what will happen on 25th April, so it will be very interesting to see how the bright light of the Full Moon is reduced by the light shadow. You should be able to see a definite darkening of the face of the Moon, and of course the much deeper darkening of a slight part of the left edge will be another challenge worth waiting for.
The April 25 lunar eclipse will begin at 9:03 pm when the Full Moon will be in the middle of the eastern sky. It will become progressively darker until 10:54 when the Moon will be fully inside the penumbra and a small part of its northern edge will enter the dark penumbra. Maximum eclipse is at 11:07 pm with the left edge remaining dark for 25 minutes until 11:21 pm. During this period, the rest of the Full Moon will still be completely inside the penumbra, causing a significant reduction in the brightness of the Moon.
The other two lunar eclipses are penumbral eclipses in which only a small part of the Moon comes inside the faint shadow, hence it is not easy to notice any darkening of the face of the Moon. The first of these, on May 25, 2013 will follow the annular solar eclipse of 10th May, and will be centred over the Americas lasting from 6:53 am to 7:27 am with only a slight edge of the Moon entering the penumbra. This eclipse will also not be noticeable from Tanzania. The second one, centred over West Africa, will take place after midnight at 0:50 am of October 19, and will end 4:49 am. At maximum eclipse at 2:51 am, when more than two thirds of the Moon will be dipped inside the penumbra. Keen observers may be able to notice a difference in the brightness of the Full Moon that night.
A most eagerly awaited astronomical event is awaited in November when an extremely bright comet is expected to make an appearance. Comet ISON, discovered last September when it was about 2 billion kilometres from earth, is shaping up to make a spectacular show when it reaches within 2 million kilometres from the Sun (i.e. within the Sun’s outer atmosphere) on November 28. If it is not torn apart by the Sun’s gravitational force which can zip it at speeds of more than half a million kilometres per hour, it can become the brightest object in the sky, visible even in daylight. The ice that a comet is made up of evaporates as it gets heated by the Sun and the solar wind pushes the fine dust in the comet to extend millions of kilometres, giving the comet its long, tailed shape when observed from Earth. This comet is current a focus of astronomers around the world who are closely monitoring it how it shapes up as it progresses towards us.
Among the planets, Jupiter starts the year bright in overhead skies and will remain visible until the beginning of June. Saturn is a morning star at the moment shining in the west. It enters the evening skies in mid April rising in the east in the in early evening and remains in the skies, shifting westwards, until the beginning of October when it slips out of the evening skies. The planet appears in the sky as a sharply shining star distinguishable from other stars because it does not twinkle. Mars starts the year visible as a faint red star in the western evening skies until March when it disappears from the skies.
Venus is a morning star in January at an elevation of 20 degrees above the horizon at sunrise. It dips to lower elevations until mid February when it will be too close to the Sun to be seen. It will reappear at the beginning of May to begin shining as an evening star. By 26 May, Venus, Jupiter and Mercury will form a close triangle with Jupiter moving closer to Venus, coming closest on 28th May and the three lining up close together by 31st.
Mercury becomes unusually bright during its May appearance and it should be identifiable close to the much brighter Venus-Jupiter pair. Mercury is a planet that orbits close to the Sun so it usually does not appear very high in the sky. However, this year, it makes three remarkably high appearances when it will rise to around 20 degrees above the horizon at sunset. First of these high rises will be at the end of January up to beginning February, reaching a highest elevation of 15 degrees on January 28. The next high rise of Mercury will be from beginning May to mid June when it rises to a maximum of 20 degrees on 23rd May. The last will be from mid August to beginning October with a highest elevation of 22 degrees on 19th September.
The Moon shifts position by about 12 degrees every night and repeats its appearance every month, so it regularly takes up attractive positions next to bright planets and stars. During the Venus-Mercury encounter at the end of June, it comes close to the pair on 10th June and so Venus-Mercury-Moon will produce a remarkably attractive sight in the sky about 20 degrees above the western horizon soon after sunset.
Other notable close encounters of the Moon with planets will be on February 12 when it will be in line with Mars and Mercury. On 14th April, it will be form a triplet in line with Jupiter and the red giant star Aldebaran half way up the sky. On 8th September it will come extremely close to Spica the brightest star in Virgo constellation, with Venus close by on the opposite side.
Between 6 and 10 September, Mercury-Venus-Saturn-Moon form a line, with the Moon shifting positions among these three planets night after night. This line is the called the ecliptic, along which all planets and the Sun move in the sky. They always appear along this line in the sky since our all planets move around the Sun in a flat plane and we are looking at the sky along that plane when we watch the planets. On 6th and 7th October, the Moon forms a close triangle with Mercury and Saturn. The Moon will be full on Jan 27 and New Moon will be on February 10. Closer details will be provided as the year progresses or visit www.astronomyintanzania.or.tz if you want to plan stargazing sessions in advance.
The Globe at Night campaign which is an attempt to monitor light pollution of night skies is conducted by amateur observers around the world in the first months of the year. It makes use of the many bright stars seen at this time of the year and observers determine the state of light pollution by reporting to a central website which stars they can see from their neighbourhoods. This year, the campaign is conducted on January 3-12, January 31-February 9, March 3-12, March 31-April 9, and April 29-May 8. There are many chances for you to participate so visit the www.globeatnight.org website for further instructions.