Vernal march equinox sun crosses the celestial

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Unformatted text preview: Derives from the Latin for "equal night". Equinoxes occurs twice a year, during March and September. • Vernal (March) Equinox: Sun crosses the Celestial Equator moving North (occurs on or about March 21) • Autumnal (September) Equinox: Sun crosses the Celestial Equator moving South (occurs on or about September 21) These names have a “northern bias”, as while in June it is summer in the northern hemisphere, it is winter in the southern hemisphere (and similarly flipped during December). For this reason, the solstices and equinoxes are often referred to by the name of the month in which they occur: June Solstice, March Equinox, etc.. 7 The Sun’s changing daily path Zenith Summer Solstice NCP Vernal & Autumnal Equinoxes Winter Solstice E N S Horizon W CEq Richard Pogge Monday, October 22, 12 As we saw in our last lecture, an object’s daily path in the sky depends on its location on the celestial sphere. Therefore, the Sun’s daily path changes with the Sun’s location on the ecliptic, including: The location of sunrise and sunset. The altitude of the Sun at noon (i.e., how high it is in the sky) The amount of time the Sun is above the horizon (i.e., the number of hours of daytime) This figure shows the daily path of the Sun on the summer solstice (orange path), winter solstice (blue path), and the equinoxes (green path), as viewed from a mid-northern latitude (such as Champaign, IL). 8 At the summer sols8ce (Jun 21) ‣ ‣ ‣ Sun rises north of east Sun sets north of west Sun rises high in the sky Long days, short nights Nebraska Astronomy Applet Project. ‣ The Sun’s daily pat...
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This note was uploaded on 10/23/2013 for the course ASTR 100 taught by Professor Dunne during the Fall '12 term at University of Illinois, Urbana Champaign.

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