Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2007 January 29
See Explanation. Go online for the highest resolution available.

Movie: A Green Flash Over Italy
Credit & Copyright: Danilo Pivato (Beyond the Moon)

Explanation: How could the Sun turn green? Difficult to observe, the momentary green flash above the rising or setting sun has been documented as a phenomenon caused by the atmospheric bending or refraction of sunlight. Like a weak prism, the Earth's atmosphere breaks white sunlight into colors, bending red colors slightly and green and blue colors through increasingly larger angles. When the sky is clear, a green flash just above the sun's edge can sometimes be seen for a second or so, when the sun is close to a distant horizon. Still, from a site atop Mt. Autore (altitude 1,850 meters) in Italy astrophotographer Danilo Pivato captured this dramatic green flash movie (available online). The time between frames varies from over one minute in the beginning to about one second as the flash becomes visible.

View this page (with external links) online at
http://apod.gsfc.nasa.gov/apod/ap070129.html.


< | Archive | Index | Calendar | Education | About APOD | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Official: Phillip Newman. Specific rights apply.
A service of: ASD at NASA/GSFC
& Michigan Tech. U.

DVD Table of Contents
Educator's Index