This page is a periodic description of current events or topics that concern the Nightly Observing Program held at the Kitt Peak Visitor Center.

September

This Moonth

As a child it is humbling experience to see the moon appear to follow you during a nighttime drive. The moon is a symbol that personifies everything from the romantic to the insane. Thus culturally the moon reflects attitudes about ourselves and life on Earth. However science has found a very literal interpretation of that reflection. On the nights of September 9th-12th find the moon in the western sky after sunset. You will see the very bright sunlit portion of the crescent phase. However, once it is dark enough you will also see a ghostly gray glow that illuminates the other fraction of the moon's countenance. Imagine that from the moon the Earth is a brilliant and dazzling blue-white ball in the sky. This earthshine can be seen lighting up the otherwise dark part of the moon's phase.

The beauty of Earthshine was first explained by Leonardo Da Vinci. The earth acts as a gigantic mirror and the brightness of the Earthshine measures the reflectance of the Earth. Scientists have studied this glow to measure variations of clouds (and aerosols) in the atmosphere. For example, more clouds would reflect more light and make the earthshine brighter. The Earths climate is controlled by the amount of sunlight it absorbs. Thus, long-term variations in the brightness of Earthshine offer clues to changes in climate and perhaps global temperature fluctuations. Not bad for a pale glow that is around 240,000 miles away!

Later in the month be certain to catch the rising of the full moon after sunset on the 21st. This moon is often called a Harvest Moon because farmers used to work longer hours under its light. This autumn full moon is no larger, brighter, or closer than any other in the year. In fact each month of the year has a full moon with a less well-known name. Just don't get loony trying to keep them straight: 

January:   Old Moon     July:      Thunder Moon
February:  Snow Moon    August:    Grain Moon
March:     Crow Moon    September: Harvest Moon
April:     Grass Moon   October:   Hunter's Moon
November:  Frosty MOon  December:  Long Night Moon
For questions or future article suggestions please e-mail me at ablock@noao.

Credit: T. Credner

Adam Block
Kitt Peak Visitor Center
Lead Observer

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Updated: 06/00/2002