Coming Up: Three Supermoons!
by Farmers' Almanac Staff | Monday, May
13th, 2013 | From: Astronomy
Full
moon lovers will be in for a treat this summer as the coming months bring not
just one, but three full supermoons in a row.
A
supermoon occurs when the Moon is at least 90% of the way to its closest
approach to the Earth at the same time it is full or new. Supermoons are caused
by the shape of the Moon’s orbit, which is not a perfect circle, but an
ellipse, or oval, shape. The Moon orbits the Earth once each month, and each
month reaches a point farthest from the Earth, called apogee, and closest to
the Earth, called perigee.
The
reason these two Moon phases are singled out is because each of them means that
the Sun, Earth, and Moon are in alignment. When the Moon is full, it sits
exactly on the opposite side of the Earth from the Sun. When the Moon is new,
it sits between the Earth and the Sun. In both cases, the gravitational pull
from these two bodies – the Moon and the Sun – combine to create larger than
normal tides, called “spring tides,” on Earth. When the Moon is also at perigee
at this time, the effect is magnified into what is called a “proxigean spring
tide.”
According to NASA, a full moon at perigee is up to 14%
larger and 30% brighter than one at its furthest point (apogee). It has been claimed that the supermoon
of March 19, 2011 was responsible for the grounding of five ships in the Solent
in the UK. And within 1 or 2
weeks of a supermoon a causal relationship with specific natural disasters such
as the 2011 TÅhoku earthquake and tsunami and the 2004 Indian Ocean earthquake
and tsunami.
Of
course, a new Moon at perigee isn’t very exciting to look at – because the new
Moon does not reflect the Sun’s light, it is invisible – so full supermoons get
much more attention than new supermoons. There are usually about four or five
supermoon events each year, only about half of which tend to be full
supermoons. This year is somewhat unusual in that there are only three supermoons,
and all three are full.
May’s
full Moon falls on the 25th, one day before the lunar perigee on the 26th. The
May supermoon also coincides with a very minor partial lunar eclipse. The
largest of this year’s supermoons will occur on June 23, within 22 minutes of
the Moon’s perigee on the same day. June’s supermoon coincides with the Moon’s
closest approach to Earth until August 10, 2014. Finally, July’s full Moon will
rise on July 22, one day after that month’s lunar perigee.
With
two or three full supermoons each year, they may not be unusual events, but for
those who love looking up at the night sky, any excuse will do.
Happy
Moon gazing!
http://www.farmersalmanac.com/astronomy/2013/05/13/coming-up-three-supermoons/
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