Astronomy Highlights for Tanzania for 2017

Saturn tilt picture from:

https://astrobob.areavoices.com/2015/06/28/egg-moon-close-to-saturn-tonight-occults-theta-librae/

Four eclipses will occur during this year, with three of them visible from Tanzania. The first eclipse this year is a penumbral eclipse on midnight of February 10 to 11 from 1:34 am to 5:53 am. It will give us a similar challenge to the one we had last year on September 16. On February 26 from 6:32 pm to sunset 7:08 pm viewers in southern Tanzania will see a partial solar eclipse, though it will not be as spectacular as last year’s annular solar eclipse. The third eclipse is the Partial Lunar Eclipse of August 7 from 8:33 pm to 10:18 pm during which, a small part of the Moon will be covered by the Earth’s shadow. The last eclipse, a Total Solar Eclipse of August 21 will not be visible in Tanzania since it takes place across the whole of the USA. If you can visit there during the eclipse do not miss out on this spectacular event.

For planet viewing, the year started with a close alignment of three bright objects, Crescent Moon, Venus, and Mars, prominently, for several days near the western horizon. The Moon-Venus-Mars triplet group is together again on January 31st and the line-up continues after that until February 3.

Again, at the end of February on the 28^th, the triplet is together again though not so close together near the west horizon soon after sunset.

The Venus and Mars pair remains visible together in the evening sky for the whole of February with the pair shifting slightly rightwards over the days.

Venus is a spectacularly bright planet, now shining as an evening star. After reaching its highest elevation of 45 degrees in the sky above the western horizon, it has now entered the crescent phase and is visible as a broad crescent through a telescope. The crescent will grow thinner as well as more than double in size as the planet gets closer to Earth until mid-March, after which it will be hidden by the setting Sun. After this, Venus will enter the sky as a morning star, reaching its highest elevation above the eastern horizon in mid-May. It will remain visible before sunrise until mid-December. On November 17, Venus will form a triplet with a crescent Moon joined by bright Jupiter joining brilliant Venus to provide an attractive spectacle. After this, it will again enter the evening skies as an evening star from the beginning of February 2018. All during the year, Venus will provide many attractive views with the crescent Moon in the western sky at sunset or in the eastern sky at sunrise. Visit www.AstronomyinTanzaia.or.tz for individual events of Venus and other planets and stars during the year.

Mars is now seen as a red star with the steady shine of a planet compared to a star which twinkles. It is currently visible from soon after sunset, seen close to brilliant Venus half way up the western sky. It remains visible until mid-June when it will be too close to the sunset Sun. Then, from the end of August it will be seen in the morning sky above the eastern horizon, rising gradually. By the beginning of December, Mars will line up with Venus, Jupiter, Mars, crescent Moon, and star Spica from the beginning of December to mid-December. Mars will also provide other interesting events during the year.

Mercury is an elusive planet not easy to detect since it always remains close to the Sun; it has to be caught when it is highest in the sky. This happens twice in the western sky at sunset on April 1 and July 30, and twice in the eastern sky at sunrise on May 17 and September 12. The highest elevations of 27 degrees on May 17 and July 30 are the best times to look out for Mercury in the sky. At other times, when it is close to crescent Moon or Venus, it can also be found at the Astronomy in Tanzania website.

Jupiter, the largest planet is also extremely bright and can be mistaken for Venus but they can be differentiated by noting that Venus is always seen near the Sun just after sunset or before sunrise. Venus can never be seen in overhead skies, while Jupiter can be. Currently, Jupiter is high overhead in the morning sky and will start to be seen rising in the east at late evening hours from the end of February. By April 7 Jupiter will rise in the east at sunset while the Sun is setting in the west. This means that the fully-lit face of Jupiter shines with light from the Sun. This situation on April 7 is called opposition and the planet is most brilliant. Jupiter will then be seen higher and higher in the east at sunset as it shifts slowly westwards. It will be lost in the sunset Sun from mid-October when it will be closest to the Sun on October 26, a phenomenon called conjunction. After this, from mid-November it will be seen in the morning sky close to the eastern horizon at sunrise. Jupiter will show many memorable events during the year as it comes close to the Moon, planets, and bright stars. See www.AstronomyinTanania.or.tz for details of dates, times and positions. Through a modest telescope, Jupiter shows parallel belts of clouds and four moons that change positions day by day and even hour by hour; at times the moons are hidden behind the planet and at other times the moons’ shadows can be detected on the face of the planet through a good telescope.

Saturn, the ringed planet is also clearly visible in the sky, shining with a steady light. Though not very bright, it is the most beautiful object to view through a telescope that shows the flat ring system. This year the rings are seen particularly well since they are inclined at a maximum angle facing us. Currently, Saturn is, in the morning, half way up the eastern sky. Saturn will begin to be seen in late evening hours rising in the evening from May onwards. It will reach opposition and be brightest on June 15 when it will rise in the east at sunset, while the Sun is setting in the west. At opposition we see the full face of the planet shining directly from light reflected from the Sun. Saturn will shift westwards during the following months, visible higher and higher in the eastern sky. By September it will be in the western sky and will end the year coming close to and disappearing behind the setting Sun in the west by the beginning of December. Once again it will provide many memorable events throughout the year when it is seen close to the Moon and various planets and these can be followed on www.AstronomyinTanzania.or.tz.

The Sun shows its apparent motion throughout the year, moving 23.5 degrees north and south of the equator. It will be at the equator on March 20 and on September 22. These are called the equinoxes, since the length of day and night are equal on those dates, because the equator is directly along the plane of the solar system; so the Sun shines symmetrically on Earth. Due to the inclination of the Earth’s rotation axis that is inclined to the solar plane by 23.5 degrees, the Sun shines vertically on a latitude 23.5 degrees north (Tropic of Cancer) on June 21. This is called the northern solstice, when it is hot in the north and cold in the south. Similarly, the Sun shines vertically at latitude 23.5 degrees south (Tropic of Capricorn) on December 21 causing the hot season in the south and cold in the north. Days are longer than nights in the north from March 20 to September 22, while in the south, nights are longer than days. The opposite happens between September 22 and March 20.

The Moon changes its phase (shape) from New Moon to half Moon to Full Moon to half Moon and back again to New Moon in each lunar cycle during the year. The first half Moon phase is called the First Quarter, while the second half Moon phase is called the Last Quarter, since they mark quarters of the lunar cycle. New Moons will be on January 28, February 26, March 28, April 26, May 25, June 24, July 23, August 21, September 20, October 19, November 18, and December 18. Full Moons will be on January 12, February 11, March 12, April 11, May 11, June 09, July 09, August 07, September 06, October 05, November 04, and December 03. The First Quarter and Last Quarter half Moons will occur between the respective New Moon and Full Moon days. See detailed times here.

Public holidays that depend on the lunar cycles will also be decided on the basis of New Moon dates since the Moon is first sighted one or two days after the New Moon, depending on the elevation of the Moon above the setting Sun in the western horizon. Hence, the Idd ul Fitr dates can be expected to be on June 25 or June 26. Idd ul Hajj can be expected to be on September 1 or September 2, and Maulid can be on December 1 or December 2.

Among the nine regular meteor showers that strike earth during the year two of these can be most suitable to watch for our location near the equator and south are on few days before and after May 6 (Eta Aquarids) and December 14 (Geminid). The best time to see meteor showers is after midnight and close to sunrise. At this time, the Earth’s revolution around the Sun faces and hits the dust particles left behind by comets. This causes the dust particles to strike the atmosphere and burn up to cause shooting stars called meteors. The Moon should also be below the horizon to have a good chance of seeing meteors. Lie flat on the ground on a mat and look comfortably at the region of the sky from which the dust strikes the atmosphere. For more details of directions and times see Astronomy in Tanzania website.

Comets become active when they come near the Sun from deep space in highly elliptical paths. The Sun evaporates the frozen water and releases dust, causing a bright blob. The dust is pushed away by the sunlight which produces a tail that faces away from the Sun. Three comets can become just bright enough to be seen in dark skies on February 11 (comet 45P/Honda), May 15 (comet C/2015 ER61 PanSTARRS) and June 15 (comet C/2015 V2 Johnson), especially when seen through binoculars. For details of positions and times and tips to view the comets visit the Astronomy in Tanzania website.

The Moon hides (occults) stars when it passes in front of stars so that our line of sight is blocked and we cannot see the star for a short time. The star is eclipsed by the Moon. Three interesting occultations by the Moon occur this year on February 12 (star ZC1547 hidden), March 14 (stars X54027 and ZC1821 are hidden) and May 31 when star ZC1487 is hidden. On www.AstronomyinTanzania.or.tz you can find the exact times and positons for viewing the occultations.

Satellites make an extremely good hobby to watch. If you watch carefully and scan the overhead skies soon after sunset once it is dark enough and sky is clear; you will often see one or two points of stars moving quite visibly against the background stars. These are satellites and they are seen because light from the Sun can reach high above us where the satellites orbit, and they reflect the sunlight. Some satellites are bright while others shine on and off as their surfaces come to be at the right angles to reflect sunlight towards us. The brightest of these satellites is the International Space Station (ISS) which orbits at a height of about 400 kilometres above the Earth’s surface. It shines as bright as a plane and even Venus but glides slowly across the sky. Other prominent satellites are the Hubble Space Telescope (HST) and Iridium flares. The times and positions of viewing the satellites depends on your location and if you know your coordinates you can use websites on the Internet to find the exact times and directions of the satellites. Visit www.heavens-above.com for detailed information about all satellites and their viewing times and directions. For the ISS, which is the brightest satellite and really worth following and showing to your friends, you can use the Spot the Station NASA website which you can get from Google and follow the instruction on the NASA website after selecting the location nearest to you from Dar esSalaam or Mwanza. Visit www.AstronomyinTanzania.or.tz for regular details about when and where to see satellites stars, planets, and all other astronomy events.

Have a most happy astronomical viewing during this year 2017.

Note:

A comprehensive listing of astronomy events from Universetoday website in a PDF book format can be downloaded here. It has been written for American audiences so the times and postions of events will not be correct for Tanzania and the east African region.

101 Astronomical Events for 2017 by David A. Dickinson

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