Supermoon will rise in weekend night sky
Source: FOX News
by By Joe Rao
The largest full moon of 2013, a so-called "supermoon," will light up the night sky this weekend, but there's more to this lunar delight than meets the eye.
On Sunday, June
23, at 7 a.m. EDT (1100 GMT), the moon will arrive at perigee — the point in
its orbit bringing it closest to Earth, a distance of 221,824 miles. Now the
moon typically reaches perigee once each month (and on some occasions twice),
with their respective distances to Earth varying by 3 percent.
But Sunday's lunar
perigee will be the moon's closest to Earth of 2013. And 32 minutes later, the
moon will officially turn full. The close timing of the moon's perigee and its
full phase are what will bring about the biggest full moon of the year, a
celestial event popularly defined by some as a "supermoon
You can watch a free webcast
of 2013 supermoon full moon on SPACE.com on Sunday at 9 p.m. EDT (0100
June 24), courtesy of the skywatching website Slooh Space Camera.
While the exact
time of the full moon theoretically lasts just a moment, that moment is
imperceptible to casual observers. The moon will appear full a couple of days
before and after the actual full moon most will speak of seeing the nearly full
moon as "full": the shaded strip is so narrow, and changing in
apparent width so slowly, that it is hard for the naked eye to tell in a casual
glance whether it’s present or on which side it is.
During Sunday's
supermoon, the moon will appear about 12.2 percent larger than it will look on
Jan. 16, 2014, when it will be farthest from the Earth during its apogee.
Supermoon's big
tidesIn addition, the near coincidence of Sunday's full moon with perigee will result in a dramatically large range of high and low ocean tides. The highest tides will not, however, coincide with the perigee moon but will actually lag by up to a couple of days depending on the specific coastal location. [The Moon Revealed: 10 Surprising Facts
For example, for
New York City, high water (6.3 feet) at The Battery comes at 8:58 p.m. EDT on
Sunday, or more than 12 hours after perigee. From Cape Fear, N.C., the highest
tide (6.5 feet) will be attained at 9:06 p.m. EDT on Monday, while at Boston
Harbor a peak tide height of 12.3 feet comes at 12:48 a.m. EDT on Tuesday, almost
2 days after the time of perigee.
Any coastal storm
at sea around this time will almost certainly aggravate coastal flooding
problems. Such an extreme tide is known as a perigean spring tide, the word
spring being derived from the German springen, meaning to "spring
up," and is not — as is often mistaken — a reference to the spring season.
Spring tides occur
when the moon is either at full or new phase. At these times the moon and sun
form a line with the Earth, so their tidal effects add together (the sun exerts
a little less than half the tidal force of the moon.) "Neap tides,"
on the other hand, occur when the moon
is at first and last quarter and works at cross-purposes with the sun. At
these times tides are week.
Tidal force varies
as the inverse cube of an object's distance. We have already noted that this
month the moon is 12.2 percent closer at perigee than at apogee. Therefore it
will exert 42 percent more tidal force at this full moon compared to the spring
tides for the full moon that will coincide with apogee next January.
Huge moon at
moonrise
Usually the variation of the moon's distance is not readily apparent to observers viewing the moon directly.
Or is it?Usually the variation of the moon's distance is not readily apparent to observers viewing the moon directly.
When the perigee moon lies close to the horizon it can appear absolutely enormous. That is when the famous "moon illusion
So a perigee moon,
either rising in the east at sunset or dropping down in the west at sunrise
might seem to make the moon appear so close that it almost appears that you
could touch it. You can check out this out for yourself by first noting the
times for moonrise and moonset for your area by going to this website of moonrise times by the U.S. Navy Oceanography Portal
.
Happy moon-gazing!
1 comment:
We had that here too. It was kind of a let down. It didn't look any bigger.
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