Lunar Eclipse at sunset this Saturday

Lunar Eclipse at sunset this Saturday

Dr N T Jiwaji

ntjiwaji@yahoo.com

A lunar eclipse is a celestial event that can be observed from a large part of the world and can be witnessed simultaneously by billions of people at the same when it is taking place in space. However, this makes it seem like a common occurrence that can be taken for granted like a Moonrise. A total solar eclipse, on the other hand, is visible only within a small band about 100 kilometres wide. Hence, extremely small number of people will have witnessed a totally blacked out Sun and people are in awe of this fiery experience.

The total lunar eclipse of December 10^th is an event of significance for Tanzania since it kicks off the next 50 year era of our independence. It is also a lunar eclipse that only a few people in the world will see. In fact, the total part of the eclipse, when the whole Moon will be covered by the Earth’s shadow, will be witnessed only by people on the Asian continent.

Following the extremely dark total lunar eclipse seen high in the sky on June 15 this year, this December 10 eclipse will be a less spectacular event in Tanzania since only its end will be seen while the Full Moon rises in the east at sunset. There will also be a big difference between how much of the eclipse is seen by people in different parts of Tanzania. Those living in the east of the country will see a bigger part of the eclipse compared with what will be seen at the opposite end of the country.

In Dar es Salaam, the Moon will rise at 6:33 pm after the Sun has just set at 6:27 pm. At this time, the top left half of the Moon will be covered up by the Earth’s shadow. The Moon will continue to rise as the shadow slowly slips away. By the time the dark part of the eclipse ends at 7:18 pm, the Moon will have risen sufficiently high, to about 10 degrees, so most people in the coastal belt should be able to view the eclipse as long as the east horizon is clear of clouds or obstructions. Select a spot with a clear view with the ocean horizon in the distance, and you will be among the lucky few who will have witnessed this rare event.

By contrast, in Kigoma, the Moon rises at 7:07 pm at which time the eclipse is almost finished and only a very small part of the top left edge shadow will cover the Moon. Lacking an ocean towards the east one will need to find a sufficiently flat distant horizon to be able to view the last throes of this eclipse.

Eclipses occur when the sun, earth, and moon are exactly aligned so that shadow of one body can fall on the other. Solar eclipses occur when moon’s tiny shadow falls on a small part of our huge earth. During a lunar eclipse, the huge shadow of our Earth covers up the much smaller moon. During a total eclipse, the whole moon becomes completely immersed in the Earth’s shadow. If part of the Moon remains outside the shadow, we say that the lunar eclipse is partial, which is what we will see on Saturday of December 10 at sunset.

While you watch the lunar eclipse this Saturday, imagine the way the Sun, Earth and Moon are actually arranged in space. During the eclipse, you can see that the Sun has just set in the west and is below the horizon, and you are on Earth and the Moon is rising on the opposite side in the east. You can now picture the positions of the Sun, Earth and Moon with respect to each other and appreciate that the light from the Sun has been obstructed by our Earth and so its shadow is now falling on the Moon during the eclipse.

Follow the lunar eclipse diagram as you think about this and you will be able to understand the actual arrangement of the celestial bodies. You can also visualize the Earth’s shadow slowly slipping away from the face of the Moon as the eclipse comes to its end. You will actually be watching a celestial event while it is taking place nearly half a million kilometres away! Remember that normally during Full Moon, the Sun, Earth and Moon are not is an exact straight line so the light from the Sun is able to reach the Moon and we are able to see a Full Moon once a month.

While looking at the lunar eclipse and turning your head westwards and eastwards to understand what is happening on the Moon, do not forget to tilt your head slightly upwards to see our the two brilliant companions for several months, the planets Venus and Jupiter, shining like spotlights in the evening skies.