MadSci Network: Astronomy |
What a great question! You asked it at the best time of year, too. The moon can seem to have different colours depending on the angle that you are seeing it at, and how much stuff is floating around in the air. These red or orange moons are most common in the spring and fall because there is a great deal of pollen and dust in the air. As the light that has bounced off the moon travels through the Earth's atmosphere, these small particles scatter it. They are most effective at scattering blue light, giving the moon a reddish or orangeish colour. In the spring, the pollen comes from plants that are getting ready to reproduce, in the fall (in farming areas like where I'm from) the dust and old pollen kicked up into the air by farmers harvesting their crops hangs heavily in the air, producing a thick layer of particulates.
Another good reason for asking this question at this time of year is that, on the night of September 26, there will be a harvest moon (the first full moon of the harvest season) combined with a full lunar eclipse that will be visible from everywhere in Canada and the United States! Watch the night sky on Tuesday night, and (depending on where you are in North America) you should see the moon change colour before going dark for awhile. The lunar eclipse lasts for several hours and can be seen from anywhere in North America.
For more information, check out this Earth & Sky article.
Oops! As was pointed out to us by an alert reader, the eclipse referred to here actually happened in 1996. We apologize for any inconvenience or disappointment.
Try the links in the MadSci Library for more information on Astronomy.