The Sun is about 400 times larger than the Moon and is also 400 times further from the Earth
than the Moon, causing them to appear nearly the same size as seen from the Earth. Slight variations in the Sun and Moon`s
distance from the Earth cause the Moon to appear sometimes smaller or larger than the Sun.
The Moon's shadow has three components - the Umbra, Penumbra and Antumbra. (The Earth's
shadow has the same components, but only the penumbra and umbra play a part in eclipses.)
Solar Eclipses
The umbra is less than 250 kilometres in width at the Earth`s surface, whilst the penumbra is several thousand kilometres
wide. The umbra passes very quickly along the surface, allowing for a maximum totality of 7½ minutes. However the last 7
minute eclipse was in 1973 and the next will be in 2150. In 2009 an eclipse will cross China, E. China & the Philippine
Seas to the western Pacific Ocean and, at 6 minutes 39 seconds, has the longest duration of totality in the 21st Century.
Shanghai is on the centre line for this event.
Total Eclipses - When the moon appears large enough to completely cover the sun, a total eclipse
can occur. The darkest shadow is the central umbra and anyone in this shadow, will experience the total eclipse and will not
be able to see the Sun.
During totality observers can see solar prominences, the faint inner solar atmosphere (chromosphere), and the Sun's brilliant
outer atmosphere (coronal halo), which are too faint to be seen when any part of the bright solar disk is exposed. In addition,
the sky usually darkens enough to reveal bright stars and planets while a twilight glow circles around the horizon.
Partial Eclipses - The outer shadow, the penumbra, is not as dark as the umbra. Part of the Sun can be seen from within the penumbra which
becomes less dark the closer you get to its outer edge. Anyone within the penumbral shadow of either the Earth or the Moon,
will see a partial eclipse of the Sun.
Annular Eclipses - An antumbral shadow occurs when the umbra does not reach the Earth and the Moon appears too small to completely cover the
Sun. The antumbra is an extension of the umbra and causes an annular eclipse. For anyone within the Moon’s antumbral
shadow, the lunar disk will appear smaller than the solar disk, and the Sun will be seen as a ring (or annulus).
This bright ring of sunlight surrounding the Moon's disk does not permit phenomena such as the Sun's chromosphere and
corona, associated with total eclipses, to appear.
Lunar Eclipses
Total Eclipses - These occur when the Moon travels completely into the Earth's umbra. With the Moon's
speed of about one kilometre per second, totality may last up to 102 minutes. Time between the Moon's first contact with the
umbra and last contact, when it has completely exited the umbra, may be several hours.
The Moon doesn't completely disappear as it passes through the umbra because of the refraction of
sunlight by the Earth's atmosphere. The amount of refracted light depends on the amount of clouds or dust in the atmosphere
blocking the light. This can cause the Moon to glow with a coppery-red hue that varies from one eclipse to the next.
Partial Eclipses - If only part of the Moon enters the umbra, it is seen as a partial lunar eclipse.
Penumbral Eclipses - This type of eclipse occurs when the Moon passes through the Earth's
penumbra only. This does not cause a noticeable darkening of the Moon's surface.
A special type of penumbral eclipse is a total penumbral eclipse. The moon is completely in
the penumbra of the earth, but not in the umbra. At a total penumbral eclipse the parts of the moon closest to the umbra
are a bit darker than the rest of the moon. Total penumbral eclipses are a rare type of lunar eclipses.
Eclipses during 2009:
26th January - An annular eclipse of the Sun.
Visible as a partial eclipse from the Southern Ocean, Antartica, southern Africa, the Indian Ocean, Madagascar, southern and eastern India, part
of southwest Asia, Indonesia and Australia. The path of annularity begins in the Southern Ocean south of South Africa, crosses the Indain Ocean, southern Sumatra
and Borneo before nding in te Celebes Sea. The maximum duration of annularity is 7 minutes 54 seconds.
9th February - A penumbral eclipse of the Moon.
Visible from north America, Australasia, Asia, eastern Europe and eastern Africa.
7th July - A penumbral eclipse of the Moon.
Visible from the Americas and Australasia.
22nd July - A total eclipse of the Sun.
Visible as a partial eclipse from eastern Africa, Madagascar, Asia, part of Indonesia, north-eastern Australia and northern North Island of New Zealand.
The path of totality begins of the west coast of India, crosses India, the north of Burma, China, south of Japan and ends in the Pacific Ocean south of Hawaii.
The maximum duration of totality is 6 minutes 39 seconds occuring over the Pacific Ocean. This eclipse belongs to the SAROS 136 series which produced the
longest duration total solar eclipses of the twentieth century. Saros 136 is now past its best with the eclipses of 8th June 1937, 20th June 1955 and 30th June 1973,
all over 7 minutes long at their peak. The 6 minute+ era of this Saros ends with the total solar eclipses of 2nd August 2027 and 12th August 2045.
6th August - A penumbral eclipse of the Moon.
Visible from western Asia, Africa, Europe and the Americas.
31st December - A partial eclipse of the Moon.
Visible from Austalasia, the Indian Ocean, Africa, Europe, Iceland, the Atlantic Ocean, Greenland, northern Canada, Alaska and part of eastern Brazil.
At maximum eclipse only 8% of the Moon´s surface is obscured.
Eclipses during 2010:
15th January - An annular eclipse of the Sun.
Visible from central Africa, the Indian Ocean and Asia.
26th June - A partial eclipse of the Moon.
Visible from the Pacific Ocean, north America, Australasia and Asia.
11th July - A total eclipse of the Sun.
Visible from the Pacific Ocean and south America.
21st December - A total eclipse of the Moon.
Visible from west Africa, Europe, the Americas, Australasia and Asia.
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