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.)
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.
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 2012:
20th May - An Annular Eclipse of the Sun.
Visible as a partial solar eclipse across eastern Asia, the central and northern Pacific Ocean and North America, with the
annular track crossing China, Japan and the north Pacific Ocean ending in the south-western USA at sunset.
The point of greatest annualar eclipse occurs at 49.09º north and 176.28º east in the Bering Sea where the duration of annularity
is 5 minutes 46 seconds. The final part of the annular track reaches the Californian coastline in the early evening just south of the
border with Oregon. It then tracks across Nevada, Utah, Arizona and New Mexico, ending at sunset in Texas just before reaching the town
of Snyder. The annular phase will pass directly over Albuquerque, at an altitude of 5º, where annularity lasts 4 minutes 26 seconds.
4th June - A Partial Eclipse of the Moon.
Visible from the Pacific hemisphere with the umbra reaching 37% into the lunar disc and obscuring much of the southern lunar
hemisphere. As the event is only a partial eclipse, the orange-red glow of the lunar surface from refracted light (seen at total lunar
eclipses) will be lost in the glare from the Moon´s northern hemisphere.
13th November - A Total Eclipse of the Sun.
Visible as a partial solar eclipse across the southern Pacific Ocean. The track of totality starts at sunrise in the Northern
Territory region of Australia, crosses northern Queensland leaving the Australian coast at Oak Beach just north of Cairns, then passes north
of New Zealand. The umbral track then crosses the southern Pacific Ocean and ends at sunset before reaching the South American coastline.
The point of greatest eclipse occurs in the south Pacific Ocean 2,000 kilometres east of New Zealand at latitude 39º56.9´S and longitude
161º19.8´W where the duration of totality is 4 minutes 2 seconds and the umbral track is 178.9 kilometres wide. At Oak Beach, in northern
Queensland, first contact occurs ten minutes after sunrise with the Sun 1º above the horizon. The duration of totality here is 2 minutes
5 seconds with the Sun 13.6º above the coastal horizon at mid-totality.
28th November - A Penumbral Eclipse of the Moon.
Visible from much of the Earth´s surface, excluding South America, the eastern USA, the Atlantic Ocean and western Africa. By
its nature the penumbral dimming will be very subtle and only the northern edge of the Moon will look darker to the naked eye.
Eclipses during 2011:
4th January - A Partial Eclipse of the Sun.
Visible across Europe, Africa and central Asia. At its peak, the lunar disc will cut across 86% of the solar
diameter as observed at sunrise from northern Scandinavia.
1st June - A Partial Eclipse of the Sun.
Visible across eastern Asia, northern North America and Iceland. At its peak, the lunar disc will cut across 60% of the solar
diameter as observed from northern Russia´s Arctic coast close to midnight, in the land of the midnight summer Sun. From northern Canada
a maximum of 20% of the Sun will be covered.
15th June - A Total Eclipse of the Moon.
Visible from South America, Europe, Africa, Asia and Australia. The umbral magnitude will be 1.7 and the total phase will last
1 hour 40 minutes peaking at 20:14 UT. Observors from southern Africa to India will be best placed to see all the phases of the eclipse.
1st July - A Partial Eclipse of the Sun.
Occurs just one lunar month after the June 1st eclipse, therefore two partial solar eclipses (and one total lunar eclipse) take
place in one node - a relatively rare event. As often in these circumstances, an eclipse visible from the far north of Earth is followed by
one visible from the far south. Thus the 1st July eclipse is only visible in Antarctic waters.
25th November - A Partial Eclipse of the Sun.
Visible from South Africa, Antarctica, Tasmania and New Zealand. Only Antarctica sees a significant eclipse, varying from 35% in
South Africa and Tasmania to 90%, with the Sun on the horizon, near the South American side of the Antarctic.
10th December - A Total Eclipse of the Moon.
Visible from Eastern Europe, East Africa, Asia, Australia and the Pacific. Eastern Asia, Indonesia, Australia and Japan are best
placed for viewing the eclipse near midnight.