Did You Catch the Super Orange Moon?

Full Moon Rises Over Albert Bridge in London Credit: Getty Images

Did you catch the glorious (but somewhat ominous looking) moon last night??  If you stayed inside or worked late then you probably missed one of the coolest moon events of the year!  We had two lunar phenomenon occur at once last night.  The lunar disk was orange and it was very large.  I left work around 5:40 and noticed it almost as soon as I got onto the road.  Hanging low over the horizon was the massively enlarged orange glowing disk of the moon right in front of me!  It made me think of the people in the cars around me who have probably never paid much attention to the moon before and how last night it was practically screaming for their attention.  I imagined them seeing it and then texting someone and saying “what the hell’s wrong with the moon tonight?”  Nothing was wrong with the moon, the question should be more along the lines of “what’s wrong with our atmosphere?”

There are two separate parts to the equation that makes our moon appear so huge and orange at the same time.  One of them, the color, we can say with confidence that we understand why it happens.  The part about its apparent size is still a mystery to us.  From what we know about sunlight and our atmosphere we can say with relative confidence that we know why it appears orange, or even yellow, or red.  The strange color happens when the moon is low over the horizon when it is further away from the Earth.  The light that is being reflected off the lunar surface has to travel through more of the Earth’s atmosphere at this distance.  Combine this with any irregularity in our atmosphere caused by pollution or the amount or dust or haze in our atmosphere and the light that we see gets distorted by the particles in the atmosphere.  Usually the light we see reflected off the moon is white which is the combination of all the colors in the visible spectrum.  Under last nights atmospheric conditions however, the light is diffused and only the particles with longer wavelengths are able to make it through to our eyes.  Those longer wavelength colors are the reds, yellows, and oranges.  As the evening progresses and the moon treks higher and higher into the sky the distance the light travels decreases so the light eventually reaches our eyes as the normal white we’re used to.  If you were to watch the moon climb higher every hour you would see it gradually become more whitish as it rises and gets closer and closer to Earth.

As for the part about what makes it seem so huge at the horizon, that’s still not understood by humans.  There are several different theories out there that date back to the days of Aristotle and Ptolemy but none of them have ever proven to be true.  They vary from psychological factors and personal experience to more atmospheric theories about warped and distorted images that frankly go over my head so I won’t waste your time trying to explain them.

Theories and causes aside, the large orange full moon makes for quite a sight in the evening sky!  Coming up next month on March 19th is what astronomers call a “super” full moon where the moon will be full at perigee (closest point in its elliptical orbit to Earth) which will make it about 14% larger than a non-perigee full moon.  This is a pretty rare occurrence that hasn’t happened since 1993 so get your telescopes and filter screens ready to view that blindingly bright full moon!

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About Tim

My name is Tim Phelan. I am a nerd, amateur astronomer, sports nut, and follower of Jesus. I live in Baltimore, MD where the skies are oh so polluted with light. This is Ravens Country, Birdland, and the City that Reads, or whatever. Follow me on acrosstheuniverseinnotime.com and tphelan.wordpress.com

Posted on February 8, 2012, in Night Sky and tagged , , , . Bookmark the permalink. 2 Comments.

  1. “If you were to watch the moon climb higher every hour you would see it gradually become more whitish as it rises and gets closer and closer to Earth.”
    The moon doesn’t get closer to the Earth as the night goes on, the Earth rotates so that our position on Earth moves closer to the moon.

    • Oh semantics! I never said which body does the moving, just that the moon gets closer and closer, which it does regardless of which body does the moving (or in this case rotating).

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