SOURCE/LINK:
https://svs.gsfc.nasa.gov/Gallery/SupermoonLunarEclipseSeptember2015.html
Supermoon Lunar Eclipse
September 27-28, 2015
Supermoon Lunar Eclipse
September 27-28, 2015
[ENGLISH VERSION]
Starting on the night of September 27th, 2015, a supermoon lunar eclipse
will occur. This gallery page contains visualizations about this specific event
as well as other multimedia items about supermoons, eclipses, and NASA's Lunar
Reconnaissance Orbiter (LRO). This page will update weekly - so continue to
check here for new items.
On the night of September 27th, 2015, a supermoon lunar ecllipse will be
viewable in the night sky for those living in North and South America. Those
living in Europe and Africa can view it in the early morning hours of September
28th. This video explains what a supermoon lunar eclipse is, and how rare it
has been over the last century.
Animations
and Visualizations
On
September 28, 2015 (the night of the 27th in many places), the Moon will be
full at the same time that it is closest to Earth for the year, a coincidence
sometimes called a supermoon. As it happens, this largest Full Moon occurs
within the Earth's shadow, creating the added spectacle of a total lunar
eclipse. The Moon's orbit is very slightly elliptical and therefore somewhat
off-center relative to the Earth. Each month, the Moon passes through points in
its orbit called perigee and apogee, the closest and farthest points from the
Earth for that month. Some perigees are a little closer than others. The
closest perigee for 2015 occurs on September 28 at around 1:52 Universal Time,
when the Moon will be 356,877 kilometers (221,753 miles) away. This is only an
hour before the time of peak full Moon at 2:51 UT, when the Moon's ecliptic
longitude differs from the Sun's by exactly 180 degrees. All of this takes place
during a total lunar eclipse. The Moon makes first contact with the umbra, the
central part of the Earth's shadow, at 1:07 UT, and it doesn't completely
emerge until 4:27 UT. If we define a supermoon as a Full Moon that coincides
with the closest perigee in a given year, then supermoons occur every 14
months, with occasional skips. The anomalistic month — the time between two
perigees — is two days shorter than the cycle of phases, called the synodic
month; the perigees "lap" the phases after 14 months. Total lunar
eclipses involve a third cycle, the draconic month. The Moon's tilted orbit
crosses the Earth-Sun plane at one of two points called nodes; a draconic month
is the time it takes the Moon to return to the same node. Total lunar eclipses
happen when a node crossing coincides with a Full Moon. Only then does the
Moon's orbit carry it close enough to the Earth-Sun line to actually pass
through the shadow cast by the Earth. A supermoon eclipse requires the
alignment of all three cycles, the synodic, anomalistic, and draconic months,
and this happens every 18 years 11 days, a period known as a saros. Eclipses separated by this period tend to share certain properties and
are grouped into families, or saros series. The 2015 supermoon eclipse is the
first in Saros 137. There will be seven more supermoon eclipses in this series, the last
in December of 2141. The animation begins at the end of August showing that
perigee and Full Moon miss each other by about a day. It then shows apogee on
September 14, when the Moon is almost 32 Earth diameters away. It ends on
September 28, the day of the supermoon eclipse, when the distance to the Moon
is 28 Earth diameters. The Moon graphic in the upper left shows the change in
the Moon's apparent size as it moves closer and farther in its orbit, as well
as its copper color during the eclipse. The relative sizes of the Earth and
Moon in the main orbit graphic are exaggerated by a factor of 15 to make them
more easily visible.
On the
evening of September 27, 2015 in the Americas (early morning on September 28 in
Europe and most of Africa), the Moon enters the Earth’s shadow, creating a
total lunar eclipse, the last of four visible in the Western Hemisphere in a
span of 18 months. This animation shows the changing appearance of the Moon as
it travels into and out of the Earth’s shadow, along with the times at various
stages. Versions of the animation have been created for each of the four time
zones of the contiguous United States, as well as one for Universal Time. All
of South America and most of North and Central America will see the entire
eclipse, while those west of roughly 120°W will see it in progress at moonrise.
You won’t need special equipment to see it. Just go outside and look up! The
penumbra is the part of the Earth’s shadow where the Sun is only partially
covered by the Earth. The umbra is where the Sun is completely hidden. The
Moon's appearance isn't affected much by the penumbra. The real action begins
when the Moon starts to disappear as it enters the umbra at about 9:07 Eastern
Daylight Time. An hour later, entirely within the umbra, the Moon is a ghostly
copper color, and this lasts for over an hour before the Moon begins to emerge
from the central shadow. The view in these animations is geocentric. Because of
parallax, the Moon's position against the background stars will look a bit
different for observers at different locations on the surface of the Earth. The
Moon is in the southwestern part of the constellation Pisces.
Typically,
the Lunar Reconnaissance Orbiter (LRO) spacecraft flies over the night side of
the Moon every two hours, spending about 45 minutes in darkness. Because LRO is
powered by sunlight, it uses a rechargeable battery to operate while on the
night side of the Moon and then charges the battery when it comes back around
into daylight. During the total lunar eclipse of September 27-28, 2015,
however, LRO emerges from the night side of the Moon only to find the Sun
blocked by the Earth. LRO needs to travel an entire orbit before seeing the Sun
again, relying continuously on its battery for almost three hours. LRO won’t be
in any real danger as long as its power consumption is handled carefully.
Except for LRO's infrared radiometer, called Diviner, its scientific
instruments will be turned off temporarily, while vital subsystems like the
heaters will remain on. LRO will be closely monitored throughout the eclipse.
Diviner maps the temperature on the Moon's surface along a swath below LRO's
orbit. During the eclipse, the instrument will precisely measure the rapid temperature
changes that occur as the Moon enters and leaves the Earth's shadow. When
compared with normal daylight variations, these measurements will reveal new
details about the top centimeter (half-inch) of lunar regolith. Diviner wasn't
specifically designed for this experiment, but as scientists have gained
experience with the LRO spacecraft, they've thought of new and creative ways of
using its instruments. This animation shows the Moon as it might look through a
telescope on Earth, along with LRO’s orbit, its view of the Sun, and a fuel
gauge showing received sunlight and the battery’s charge.
On
September 28, 2015 Universal Time (the evening of the 27th for the Americas),
the Moon enters the Earth’s shadow, creating a total lunar eclipse. When viewed
from the Moon, as in this animation, the Earth hides the Sun. A red ring, the
sum of all Earth’s sunrises and sunsets, lines the Earth’s limb and casts a
ruddy light on the lunar landscape. With the darkness of the eclipse, the stars
come out. The city lights of North and South America and of western Europe and
Africa are visible on the night side of the Earth. The part of the Earth
visible in this animation is the part where the lunar eclipse can be seen.
New: Click on the image to download a high-resolution version with labels
for craters near the terminator.
The animation archived on
this page shows the geocentric phase, libration, position angle of the axis,
and apparent diameter of the Moon throughout the year 2015, at hourly
intervals. Until the end of 2015, the initial Dial-A-Moon image will be the
frame from this animation for the current hour.
Lunar Reconnaissance
Orbiter (LRO) has been in orbit around the Moon since the summer of 2009. Its laser
altimeter (LOLA) and camera (LROC) are recording the rugged, airless lunar terrain in exceptional detail,
making it possible to visualize the Moon with unprecedented fidelity. This is
especially evident in the long shadows cast near the terminator, or day-night
line. The pummeled, craggy landscape thrown into high relief at the terminator
would be impossible to recreate in the computer without global terrain maps
like those from LRO.
The Moon always keeps the
same face to us, but not exactly the same face. Because of the tilt and
shape of its orbit, we see the Moon from slightly different angles over the
course of a month. When a month is compressed into 24 seconds, as it is in this
animation, our changing view of the Moon makes it look like it's wobbling. This
wobble is called libration.
The word comes from the
Latin for "balance scale" (as does the name of the zodiac
constellation Libra) and refers to the way such a scale tips up and down on
alternating sides. The sub-Earth point gives the amount of libration in
longitude and latitude. The sub-Earth point is also the apparent center of the
Moon's disk and the location on the Moon where the Earth is directly overhead.
The Moon is subject to
other motions as well. It appears to roll back and forth around the sub-Earth
point. The roll angle is given by the position angle of the axis, which
is the angle of the Moon's north pole relative to celestial north. The Moon
also approaches and recedes from us, appearing to grow and shrink. The two
extremes, called perigee (near) and apogee (far), differ by more than 10%.
The most noticed monthly
variation in the Moon's appearance is the cycle of phases, caused by the
changing angle of the Sun as the Moon orbits the Earth. The cycle begins with
the waxing (growing) crescent Moon visible in the west just after sunset. By
first quarter, the Moon is high in the sky at sunset and sets around midnight.
The full Moon rises at sunset and is high in the sky at midnight. The third
quarter Moon is often surprisingly conspicuous in the daylit western sky long
after sunrise.
Celestial north is up in
these images, corresponding to the view from the northern hemisphere. The
descriptions of the print resolution stills also assume a northern hemisphere
orientation. (There is also a south-up version of this page.)
From this birdseye view,
it's somewhat easier to see that the phases of the Moon are an effect of the
changing angles of the sun, Moon and Earth. The Moon is full when its orbit
places it in the middle of the night side of the Earth. First and Third Quarter
Moon occur when the Moon is along the day-night line on the Earth.
The First Point of Aries is
at the 3 o'clock position in the image. The sun is in this direction at the
spring equinox. You can check this by freezing the animation at the 1:03 mark,
or by freezing the full animation with the time stamp near March 20 at 23:00
UTC. This direction serves as the zero point for both ecliptic longitude and
right ascension.
The north pole of the Earth
is tilted 23.5 degrees toward the 12 o'clock position at the top of the image.
The tilt of the Earth is important for understanding why the north pole of the
Moon seems to swing back and forth. In the full animation, watch both the orbit
and the "gyroscope" Moon in the lower left. The widest swings happen
when the Moon is at the 3 o'clock and 9 o'clock positions. When the Moon is at
the 3 o'clock position, the ground we're standing on is tilted to the left when
we look at the Moon. At the 9 o'clock position, it's tilted to the right. The
tilt itself doesn't change. We're just turned around, looking in the opposite
direction.
The subsolar and sub-Earth
points are the locations on the Moon's surface where the sun or the Earth are
directly overhead, at the zenith. A line pointing straight up at one of these
points will be pointing toward the sun or the Earth. The sub-Earth point is
also the apparent center of the Moon's disk as observed from the Earth.
In the animation, the blue
dot is the sub-Earth point, and the yellow dot is the subsolar point. The lunar
latitude and longitude of the sub-Earth point is a measure of the Moon's
libration. For example, when the blue dot moves to the left of the meridian
(the line at 0 degrees longitude), an extra bit of the Moon's western limb is
rotating into view, and when it moves above the equator, a bit of the far side
beyond the north pole becomes visible.
At any given time, half of
the Moon is in sunlight, and the subsolar point is in the center of the lit
half. Full Moon occurs when the subsolar point is near the center of the Moon's
disk. When the subsolar point is somewhere on the far side of the Moon,
observers on Earth see a crescent phase.
The Moon's orbit around the
Earth isn't a perfect circle. The orbit is slightly elliptical, and because of
that, the Moon's distance from the Earth varies between 28 and 32 Earth
diameters, or about 356,400 and 406,700 kilometers. In each orbit, the smallest
distance is called perigee, from Greek words meaning "near earth,"
while the greatest distance is called apogee. The Moon looks largest at perigee
because that's when it's closest to us.
The animation follows the
imaginary line connecting the Earth and the Moon as it sweeps around the Moon's
orbit. From this vantage point, it's easy to see the variation in the Moon's
distance. Both the distance and the sizes of the Earth and Moon are to scale in
this view. In the full-resolution frames, the Earth is 50 pixels wide, the Moon
is 14 pixels wide, and the distance between them is about 1500 pixels, on
average.
Note too that the Earth
appears to go through phases just like the Moon does. For someone standing on
the surface of the Moon, the sun and the stars rise and set, but the Earth
doesn't move in the sky. It goes through a monthly sequence of phases as the
sun angle changes. The phases are the opposite of the Moon's. During New Moon
here, the Earth is full as viewed from the Moon.
The animations on this page illustrate the Moon’s orbit and its role in
lunar and solar eclipses. A solar eclipse happens when the Moon’s shadow falls
on the Earth, while a lunar eclipse happens when the Earth’s shadow falls on
the Moon. Eclipses can only happen at New and Full Moon, when the Earth, Moon,
and Sun are all in a straight line. But they don’t happen every New and Full
Moon, because the Moon’s orbit is tilted by about 5 degrees. As the Earth and
Moon travel around the Sun, the tilt of the Moon’s orbit changes direction
relative to the Sun. This is analogous to the way the tilt of the Earth causes
seasons. Just like winter and summer happen every six months, eclipses tend to
occur on a roughly six-month cycle. Unlike most eclipse shadow diagrams, the
first three animations here don’t greatly exaggerate the scale of the Earth and
Moon. They are only 2x their true scale. The view is exactly perpendicular to
the Earth-Sun line. The angle of the Moon’s orbital tilt and the “tapering” of
the shadows are both accurate. The orbit happens to be calculated for the
months preceding the April 15, 2014 total lunar eclipse.
On August 10, 2014, the Moon will be full at the same time that it is
closest to Earth for the year. This coincidence is sometimes called a supermoon. The Moon's orbit is very slightly elliptical and therefore somewhat
off-center relative to the Earth. Each month, the Moon passes through points in
its orbit called perigee and apogee, the closest and farthest points from the
Earth for that month. Some perigees are a little closer than others. The
closest perigee for 2014 occurs on August 10 at around 17:49 Universal Time,
when the Moon will be 356,896 kilometers (221,765 miles) away. As it happens,
this is only a few minutes before the time of peak full Moon at 18:10 UT, when
the Moon's ecliptic longitude differs from the Sun's by exactly 180 degrees.
How often does this happen? The period between perigees, called the anomalistic
month, is 27.55 days, on average, while the time between Full Moons, called the
synodic month, is 29.53 days. These two periods sync up every 413 days, or 1.13
years. 15 anomalistic months are about as long as 14 synodic months, so that's
how often the pattern repeats. Recently, a much broader definition of
"supermoon" has taken hold. It includes both Full and New Moons, and
perigee merely needs to be "close enough," generally within a couple
of days. By this definition, there are six or seven supermoons every year, half
of which can't be observed. Not so super! The actual shape of the Moon's orbit
is another source of confusion. The orbit is often depicted as an almost
cigar-shaped ellipse, but this is a misleading exaggeration. If you were to
draw the orbit on a sheet of paper, its deviation from a perfect circle would
be less than the thickness of your pencil point. The 50,000 kilometer (30,000
mile) difference between perigee and apogee is almost entirely due to the orbit
being off-center. The difference between the semimajor and semiminor axes is
less than 1000 kilometers (600 miles). The animation begins in mid-July,
showing that perigee and Full Moon miss each other by about a day. It then
shows apogee on July 28, when the Moon is almost 32 Earth diameters away. It
ends on August 10, the day of the supermoon, when the distance to the Moon is
28 Earth diameters. The Moon graphic in the upper left shows the change in the
Moon's apparent size as it moves closer and farther in its orbit. (The relative
sizes of the Earth and Moon in the main orbit graphic are exaggerated by a
factor of 15 to make them more easily visible.)
11 animations of the Lunar Reconnaissance Orbiter's (LRO) journey around
the Moon.
==//==
[PORTUGUESE VERSION]
SOURCE/LINK: http://www.galeriadometeorito.com/2015/08/eclipse-lunar-total-setembro-2015.html#.VgdRYX1XnIU
A verdadeira Super Lua acontece no fim de setembro, e algo raro chamará a atenção nesse dia!
31/08/15 - No dia 27 de
setembro de 2015, além da Super Lua, teremos um Eclipse Lunar Total!
Muitos observadores chamaram a Lua Cheia do final de agosto de Super Lua, isso porque foram menos de 24 horas que separaram o momento em que ela ficou 100% iluminada (cheia) e o momento do perigeu (máxima aproximação com a Terra). E se essa Lua Cheia já chamou a atenção de muita gente, no dia 27 de setembro de 2015 será ainda melhor! Mas por que?
A Lua Cheia de 27 de setembro estará a menos de uma hora da máxima aproximação da Lua com a Terra, portanto, ela parecerá ainda maior no céu noturno, e pra fechar com chave de ouro, nessa mesma noite teremos um Eclipse Lunar Total! Serão dois grandes eventos astronômicos numa única noite! Além do mais, pra tudo ficar ainda melhor, esse Eclipse Lunar Total do dia 27 de setembro de 2015 será visível em grande parte do mundo, inclusive em todo Brasil!
|
A imagem mostra a visibilidade do
Eclipse Lunar Total
no dia 27 de setembro de 2015. As partes escuras do mapa não poderão observar esse eclipse. Créditos: NASA |
Na internet encontramos informações
de que esse Eclipse Lunar acontecerá no dia 28 de setembro, mas isso por que de
acordo com o horário internacional (UTC) já será dia 28 de setembro. Mas não se
engane, pois no Brasil será dia 27 de setembro.
Também conhecida como Lua de Sangue, esse Eclipse Lunar será o último da tétrade atual. O primeiro Eclipse da Tétrade aconteceu no dia 15 de abril de 2014; o segundo no dia 8 de outubro de 2014; o terceiro no dia 4 de abril de 2015, e o último será agora, no dia 27 de setembro de 2015. E se o tempo não ajudar, não se preocupe, pois teremos uma transmissão ao vivo aqui em nosso site! Para não perder o evento, basta confirmar sua presença clicando aqui, assim você será notificado(a) quando ele estiver próximo!
O que é a Tétrade de Eclipses Lunares?
A Tétrade de Eclipses Lunares é uma série de quatro Elipses Lunares Totais que acontecem em uma determinada época. A última Tétrade foi em 2003 e 2004, e só acontecerão mais sete tétrades como essa no século atual.
Algo ruim vai acontecer no dia 27 de setembro de 2015?
Não. Será apenas mais um Eclipse Lunar Total, um evento que sempre ocorreu e continuará acontecendo em determinadas épocas. No passado remoto, quando a sociedade não tinha um bom entendimento dos eventos celestes, os Eclipses eram vistos como presságio de desastres, assim como os cometas. Além disso, um livro publicado 2013 por John Hagee, intitulado "As Quatro Luas de Sangue: Algo está prestes a mudar", fez com que superstições como essa ganhassem ainda mais força.
|
Eclipse Lunar Total 'Lua de Sangue' do
dia 14 de abril de 2014
Créditos: NASA / Griffith Observatory |
Na verdade, o termo Lua de Sangue se refere a tonalidade avermelhada que a Lua ganha em alguns Eclipses Lunares Totais (não em todos). Portanto, o correto seria chamar um Eclipse Lunar Total de "Lua de Sangue" apenas se ele já aconteceu, e se a Lua realmente ganhou a famosa coloração avermelhada, pois não há como ter certeza se isso vai ou não acontecer...
Então, se a Super Lua de agosto já chamou a sua atenção, prepare-se para a Super Lua com Eclipse Lunar Total do dia 27 de setembro, pois será um verdadeiro espetáculo!
