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August 2015 - Water on Asteroids?
Report #6 - July 2015
Our Moon's Occasional Red Beauty
Blood Moon: Our moon in a "style" of red.
The "Blood" in Our Moon
Lunar eclipses are truly beautiful, breathtaking sights. The red cascade upon the moon is what gives it its lunar eclipse nickname, "Blood Moon." While our moon red is not an everyday sight, how does it change from an iridescent, white glowing figure to one of a bold, blood-like red? This week, SC Messier gives you a detailed explanation to how lunar eclipses make their show, all using NASA's gathered knowledge on the moon and its given locations while a lunar eclipse is in full swing.
Lunar Eclipses in a Nutshell
How do lunar eclipses occur? What gives the moon its red/orange color?
Simple. Lunar eclipses occur when the moon lines directly in the Earth's shadow and filtered sunlight passes through Earth's atmosphere and illuminates/reflects upon the moon's disk, creating a red/orange hue on the moon's surface.
How it Works
First, we must fimiliarize ourselves with the eight phases of the moon, a monthly event in which the moon undergoes a change in its shadow based on the location of its orbit and position from the sun. As a result, each day during this cycle, we notice a change in the moon's appearence. Each phase has it own names from "waxing gibbous" to "half moon."
These images illustrate moon's change in appearence over the course of a month from Earth.
The eight phases of the moon.
While this cycle of phases occurs every 29.5 days approximately, there is a time, roughly every two years, in which the moon travels directly in Earth's shadow, displaying to Earth's inhabitants a completely different slight: a red moon! Unlike the phases, which take place over the course of a month, this every-two-year phenomenon only lasts for a short period of time, varying between as long as an hour, or as short as five minutes. From Earth, we'll see a color, gradient-like show in which the moon gradually transforms from its normal appearence of white to an abnormal red, and then back again. Such a sight is known as a lunar eclipse. We can see how this all works by zooming out and looking in from space.
First, the moon passes through the penumbra, Earth's extended shadow, and appears slightly dim. During this time, the moon appears as white, but what makes it dimmer in this stage of the lunar eclipse is the fact that, in the penumbra, only partially is the sun's direct light covered by Earth, still allowing the moon's disk to reflect the sun's bright light, but not 100%, making the moon appear darker to us from Earth and lose some of its standard brightness.
The moon passing through the penumbra.
Penumbra
Second, the moon then passes through the umbra, Earth's central shadow. Under the umbra, the moon is completely shielded from the sun, for the umbra is the shadow where direct light from the sun is completely blocked. As said earlier, the physical state of the moon being completely blocked from the sun is not what gives it its red glow, but the filtered light from the sun that passes through the Earth's atmosphere. Shorter wavelengths of sunlight that have passed through Earth's atmosphere are blue, while the longer wavelenghts that reach the moon are red, giving the moon a red look instead of green, for example.
Umbra
The moon passing through the umbra.
This is the time when the lunar eclipse comes to a close, particularly when the moon leaves the umbra and makes its ways out of the pernumbra on the other side of Earth. By then, the moon would have already regained its previous color and brightness. Lunar eclipses are quick sights, so catch them fast before you miss the view!
The wavelengths of filtered sunlight passing through Earth's atmosphere.
This image helps to illustrate where the central shadow, the umbra, and extended shadow, the penumbra, is in correspondence to Earth and the moon.
A lunar eclipse photographed in phases.
"NASA| Lunar Eclipse Essentials" Youtube Video
Watch this video for an overall summary of how a lunar eclipse occurs
The Significance of this Report
In general, the movement and whereabouts of our moon are very important. It's crucial to be aware of the phases and changes in the moon for further research in the celestial body itself and our solar system. Lunar eclipses truly are an amazing event for all and something to look forward to. In fact, speaking of looking forward to lunar eclipses, a very short five-minute lunar eclipse is said by NASA to present itself in parts of North America, South America, Australia, and Asia on April 4, 2015. However, we can go buckle our seatbelts for the next lunar eclipse that is expected to show on September 28, 2015. This eclipse is observed to last an hour! So bring the popcorn and your favorite telescope and get ready to witness the moon's red beauty.
SOURCES:
NASA's Goddard Space Flight Center
http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11828
http://www.nbcnews.com/science/space/moon-day-skywatchers-catch-blood-moon-eclipse-mars-n78411
http://astropixels.com/ephemeris/phasescat/phasescat.html
http://www.cambridgeincolour.com/tutorials/moon-night-calculator.htm
http://earthsky.org/space/why-does-the-moon-look-red-during-a-total-lunar-eclipse