- Baily's beads
As the
moon "grazes" by theSun during asolar eclipse , the rugged lunar topography allows beads of sunlight to shine through in some places, and not in others. This effect is called "Baily's beads", in honour ofFrancis Baily , who first provided an exact explanation of the phenomenon in 1836. [cite book |last=Littmann |first=Mark |authorlink=Mark Littmann |coauthors=Willcox, Ken; Espenak, Fred |title=Totality - Eclipses of the Sun |year= 1999 |publisher=Oxford University press |language=english |isbn=0195131797 |pages=65-66]Lunar topography has considerable relief because of the presence of mountains, craters, valleys, etc. The irregularities of the lunar limb profile (the "edge" of the Moon, as seen from a distance) are known accurately from observations of grazing
occultation s ofstar s. Astronomers thus have a fairly good idea which mountains and valleys will cause the beads to appear in advance of the eclipse. While Baily's beads are seen briefly for a few seconds at the center of the eclipse path, their duration is maximized near the edges of the path of theumbra , reaching 1–2 minutes.The Baily's beads phenomenom is seen during the credit opening sequence of the NBC TV show Heroes.
External links
* [http://umbra.nascom.nasa.gov/eclipse/980226/rp.html Reference Publication on the Total Solar Eclipse of 1998 February 26.]
* [http://www.exploratorium.edu/eclipse/what2.html What to See During an Eclipse Continued.]References
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