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

March 2002

Twilight Thoughts

A sunset on a clear day here in the southwest is truly awe inspiring. As the sun nears the horizon the colors of the sky change from the vibrant blues of mid-day to the muted lavender and pink tones of twilight. These colors seem to be Nature's way to saying "Shhhhh" as night begins. When the sun sets (5-10 minutes after) if you look towards the East opposite the sun you will notice the sky just above the horizon is colored too. Generally you will see a line of pink with a dark blue layer beneath. Many people attribute this pink/blue division with pollution from the city. However, the phenomenon is quite natural. The pink layer is the part of sky (upper atmosphere) that still sees the reddened rays of the sun while the lower dark blue portion is the Earth's shadow cast by the horizon from the west. As the sky darkens and the sun is further beneath the horizon the Earth's shadow will rise higher into the sky until you can no longer see it because it is night. This symphony of color plays in reverse right before sunrise in the western morning sky.

While you are admiring the sunsets this month, be sure to notice the bright "star" low in the western sky. This is actually the planet Venus and this month it emerges from the glare of the Sun. Venus is on an inner track in the solar system and for the next few months it will race towards the East as it tries to catch up to us here on the Earth. Thus, it will be higher in the sky week after week until in the late summer Venus passes us and sinks towards the sun again in an e ndless celestial marathon.

Adam Block
Kitt Peak Visitor Center
Lead Observer

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Telescope Operators/Guides for Nightly Program:
Adam Block (ablock@noao.edu) Lead Observer
Flynn Haase (fhaase@noao.edu)
Ethan Gargiulo (gargiulo@noao.edu)
Richard Barchfield (richardb@noao.edu)
Jack Kennedy (jkennedy@noao.edu)
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Updated: 1/28/2001