GET READY FOR SEPTEMBER EQUINOX

Rainbow Shower sunsets solstice equinox

Bringing Heavens Down to Earth: Sun’s Paths through Solstices and Equinoxes at the Rainbow Shower

It is the summer’s great last heat,
It is the fall’s first chill: They meet.

–Sarah Morgan Bryan Piatt

At 7:29 PM Phoenix time this evening, the summer will pass into the fall in the northern hemisphere. And  winter will give birth to spring Down Under (Sept 23 at 2:29 UTX; 10:29 PM EDT; 7:29 PM PDT on Monday, the 22nd).

As we get ready to welcome the official start of the fall season this evening, thought I’d illustrate for you the play of solstices and equinoxes through the sunset skylines of the Rainbow Shower in Maui, Hawaii. The above panorama is a blended shot of the summer and winter sunset.  The viewing direction is due west.

I have superimposed on it the sun’s setting path in each of the the four seasons.

Sunset2_06_11-1 Sunset_Panorama6_25_11

The word equinox comes from the Latin words for “equal night.” The fall and spring equinoxes are the only days of the year in which the Sun crosses the celestial equator. The Sun crosses the celestial equator going southward; it rises exactly due east and sets exactly due west.

To learn more about this semiannual phenomenon, click on this Sky and Telescope link.

Earth’s spin axis isn’t perpendicular to the plane of its orbit around the Sun. One consequence: the celestial-coordinate system is tilted 23½° with respect to the ecliptic (the path followed by the Sun through the stars over the course of a year). Equinoxes occur when the Sun crosses from one hemisphere to the other.

 

 

 

 

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