Why Was September’s Lunar Eclipse So Dark?

245 views Leave a comment

First off, a huge thank you to everybody who done and sent their Danjon scale guess of a totally-eclipsed Moon’s liughtness to Dr. Richard Keen, University of Colorado windy scientist.

The Sep 17, 2015 sum lunar obscure was darker than expected. Several factors including a Moon’s plcae in Earth’s shade and volcanic dirt might have been during play. This print was taken in Washington’s Olympic National Park during totality. Credit: Rick Klawitter

The Sep 17, 2015 sum lunar obscure was darker than expected. Several factors including a Moon’s plcae in Earth’s shade and volcanic dirt might have been during play. This print was taken in Washington’s Olympic National Park during totality. Credit: Rick Klawitter

Your information were essential to his investigate of how aerosols in Earth’s atmosphere and other factors change a Moon’s appearance.

Grateful for your help, Keen perceived a sum of 28 observations from 7 opposite countries.

Graph combined by Dr. Richard Keen plotting Danjon L values submitted by Universe Today readers and others that review likely values (top curve) with celebrated values. The Moon was about half as splendid during assemblage as approaching with L=1.9. Credit: Dr. Richard A. Keen

Graph combined by Dr. Richard Keen plotting Danjon L values submitted by Universe Today readers and others that review likely values (top curve) with celebrated values. The Moon was about half as splendid during assemblage as approaching with L=1.9. Credit: Dr. Richard A. Keen

Using a Danjon information and estimates of a Moon’s brightness using a retreat binocular method, Keen crunched a information and resolved that a Moon was about 0.7 L (Danjon) units darker than approaching and 0.5 bulk dimmer, a liughtness rebate of 40%. This agrees good with my possess observation and presumably yours, too. No consternation so many stars sparkled near the Moon that night.

Lunar obscure liughtness is rated on a Danjon scale where “0” equals a dim gray assemblage and “4” a bright, coppery yellow. Credit: Bob King

Lunar obscure liughtness is rated on a Danjon scale where “0” equals a dim gray assemblage and “4” a bright, coppery yellow. Credit: Bob King

I consider it’s protected to say, many of us approaching a normal or even splendid totality. So because was it dark? Several factors were during play — one to do with a Moon’s plcae in Earth’s shadow, a other with a volcanic tear and a third with long-term, manmade pollution.

During a perigean eclipse, a Moon passes some-more deeply into Earth’s shade compared to one that happens nearby apogee, when a moon is many apart from Earth. Moon distances not to scale and for painting only. Credit: Bob King

During a perigean eclipse, a Moon passes some-more deeply into Earth’s shade compared to one that happens nearby apogee, when a moon is many apart from Earth. Moon distances not to scale and for painting only. Credit: Bob King

You’ll remember that a obscure occurred during lunar perigee, when a Moon swings closest to Earth in a 27-day orbit. Being closer, it also tracked deeper into Earth’s umbra or middle shade that narrows a over behind of a world it goes. An apogean Moon (farthest from Earth) passes by a some-more slim cone of darkness closer to a penumbra, where object mixes with shadow. A Moon nearer Earth would find a umbral shade roomier with a light-leaking penumbra further off in a distance.

On Apr 24, 2015, NASA’s Terra satellite acquired this print of a charcoal and gas plume from Calbuco volcano in southern Chile. Credit: NASA

On Apr 24, 2015, NASA’s Terra satellite acquired this print of a charcoal and gas plume from Calbuco volcano in southern Chile. Credit: NASA

But there’s more. Working independently, Steve Albers of NOAA and Brazilian astronomer Helio Vital suggested another reason: aerosols in a atmosphere. “Earth’s stratosphere is no longer totally purify of volcanic ashes,” said Vital in an e-mail communication. “In fact, slow aerosols (ash, dust, sulfuric poison droplets) from a blast of Calbuco 5 months ago might be to censure for that extreme darkening.”

With a lunar setting in a foreground, a Earth passes in front of a Sun on Sep 27, 2015 in this simulation, divulgence a red ring of sunrises and sunsets along a prong of a world obliged for educational a Moon during a eclipse. The clarity of a stratosphere during obscure time can severely impact lunar liughtness during totality. The Earth and Sun are in Virgo for observers on a Moon with a splendid star Beta Virginis during top. Click to see a video. Credit: NASA’s Scientific Visualization Studio

With a lunar setting in a foreground, a Earth passes in front of a Sun on Sep 27, 2015 in this simulation, divulgence a red ring of sunrises and sunsets along a prong of a world obliged for educational a Moon during a eclipse. The clarity of a stratosphere during obscure time can severely impact lunar liughtness during totality. The Earth and Sun are in Virgo for observers on a Moon with a splendid star Beta Virginis during top. Click to see a video. Credit: NASA’s Scientific Visualization Studio

While many of a waste bloody into a stratosphere done for colorful sunsets in a southern hemisphere, some of that element has likely made a approach to a northern hemisphere. Albers has noticed an boost in yellow and purple sunsets in his home city of Boulder in new months, telltale signs of volcanic pour during play.

Forest fires that raged opposite a western states and Canadian provinces all open and summer might also have contributed. Most of that fume customarily stays in a reduce partial of a atmosphere, though some might have found a approach to a stratosphere, a really covering obliged for transmitting many of a object that falls into Earth’s shade and colors a moon.

Graph display bulk estimates of a Moon’s liughtness during assemblage regulating a retreat binocular method. The likely bulk was -1.7 (a small brighter than Sirius) vs. a celebrated -1.3. Credit: Dr. Richard A. Keen

Graph display bulk estimates of a Moon’s liughtness during assemblage regulating a retreat binocular method. The likely bulk was -1.7 (a small brighter than Sirius) vs. a celebrated -1.3. Credit: Dr. Richard A. Keen

Sunlight has to pass by these light-absorbing minerals and chemicals on a approach by a atmosphere and into Earth’s shadow. Less light means a darker moon during sum eclipse. Coincidentally, many of a totally eclipsed Moon upheld by a southern half of a umbra that “increased a efficacy of a Calbuco aerosols (which are still some-more strong in a southern hemisphere than a northern) during dimming a light within a umbra,” writes Keen.

Oceanus Procellarum and Mare Imbrium are large, dim volcanic plains that contributed to a Moon’s queasiness and dark-hued totality. Credit: Bob King

Oceanus Procellarum and Mare Imbrium are large, dim volcanic plains that contributed to a Moon’s queasiness and dark-hued totality. Credit: Bob King

It also so happened that a darkest partial of a moon coincided with two vast, dark volcanic plains called Oceanus Procellarum (Ocean of Storms) and Mare Imbrium, artificially enhancing a altogether dejection over the northern half of a Moon.

U.S. satellite-derived map of PM2.5 (fine particulate matter that includes sulfates and soot) averaged over 2001-2006. Credit: Dalhousie University, Aaron outpost Donkelaar

U.S. satellite-derived map of PM2.5 (fine particulate matter that includes sulfates and soot) averaged over 2001-2006. Credit: Dalhousie University, Aaron outpost Donkelaar

Finally, a tellurian palm might also have played a purpose in lunar tone and brightness. The blazing of spark and oil has caused a light boost in a volume of human-made sulfate aerosols in a atmosphere given a start of a industrial revolution. According to NASA, during stream prolongation levels, human-made sulfate aerosols are believed to transcend a naturally constructed sulfate aerosols. No warn that a thoroughness of aerosols is top in a northern hemisphere where many industrial activity is found.

Isn’t it fascinating that one blood-red Moon can tell us so many about a atmosphere we breathe?

Source: Universe Today, created by Bob King