Subj : Daily APOD Report To : All From : Ben Ritchey Date : Sun Sep 23 2018 07:55:22 Astronomy Picture of the Day Astronomy Picture of the Day Discover the cosmos! [1] Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2018 September 23 [2] Equinox: Analemma over the Callanish Stones Image Credit & Copyright: Giuseppe Petricca [3] Explanation: Does the Sun return to the same spot on the sky every day at the same time? No. A more visual answer to that question is an analemma [4] , a composite image taken from the same spot at the same time over the course of a year. The featured analemma was composed from images taken every few days at 4 pm near the village of Callanish [5] in the Outer Hebrides [6] in Scotland [7] , UK [8] . In the foreground are the Callanish Stones [9] , a stone circle built around 2700 BC during humanity's Bronze Age [10] . It is not known if the placement of the Callanish Stones [11] has or had astronomical significance. The ultimate causes for the figure-8 [12] shape of this an all analemmas are the tilt of the Earth axis [13] and the ellipticity [14] of the Earth's orbit [15] around the Sun [16] . At the solstice [17] s, the Sun will appear at the top or bottom of an analemma. Equinox [18] es, however, correspond to analemma middle points -- not the intersection point. Today at 1:54 am (UT [19] ) is the equinox [20] ("equal night"), when day and night are equal over all of planet Earth. Many cultures celebrate [21] a change of season at an equinox [22] . Tomorrow's picture: parts of the sun are missing ------------------------------------------------------------------------------- < [23] | Archive [24] | Submissions [25] | Index [26] | Search [27] | Calendar [28] | RSS [29] | Education [30] | About APOD [31] | Discuss [32] | > [33] ------------------------------------------------------------------------------- Authors & editors: Robert Nemiroff [34] (MTU [35] ) & Jerry Bonnell [36] (UMCP [37] ) NASA Official: Phillip Newman Specific rights apply [38] . NASA Web Privacy Policy and Important Notices [39] A service of: ASD [40] at NASA [41] / GSFC [42] & Michigan Tech. U. [43] ---------- Site notes: [1] archivepix.html [2] image/1809/CallanishAnalemma_Petricca_1280.jpg [3] mailto: gmrpmail @a@t@ gmail .d.o.t. com [4] https://en.wikipedia.org/wiki/Analemma [5] https://en.wikipedia.org/wiki/Callanish [6] https://en.wikipedia.org/wiki/Outer_Hebrides [7] https://en.wikipedia.org/wiki/Scotland [8] https://en.wikipedia.org/wiki/United_Kingdom [9] https://en.wikipedia.org/wiki/Callanish_Stones [10] https://en.wikipedia.org/wiki/Bronze_Age [11] https://www.youtube.com/watch?v=mkbEhp8hJN8 [12] ap160822.html [13] https://spaceplace.nasa.gov/seasons/en/ [14] http://mathworld.wolfram.com/Ellipse.html [15] http://bhenvis.nic.in/images/season_climate.jpg [16] https://solarsystem.nasa.gov/solar-system/sun/exploration/ [17] ap170621.html [18] ap170319.html [19] https://eclipse.gsfc.nasa.gov/SEhelp/TimeZone.html [20] https://en.wikipedia.org/wiki/Equinox [21] http://mentalfloss.com/article/59049/autumnal-equinox-traditions [22] ap160320.html [23] ap180922.html [24] archivepix.html [25] lib/apsubmit2015.html [26] lib/aptree.html [27] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search [28] calendar/allyears.html [29] /apod.rss [30] lib/edlinks.html [31] lib/about_apod.html [32] http://asterisk.apod.com/discuss_apod.php?date=180923 [33] ap180924.html [34] http://www.phy.mtu.edu/faculty/Nemiroff.html [35] http://www.phy.mtu.edu/ [36] https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html [37] http://www.astro.umd.edu/ [38] lib/about_apod.html#srapply [39] https://www.nasa.gov/about/highlights/HP_Privacy.html [40] https://astrophysics.gsfc.nasa.gov/ [41] https://www.nasa.gov/ [42] https://www.nasa.gov/centers/goddard/ [43] http://www.mtu.edu/ --- Mystic BBS v1.12 A39 (Windows/32) * Origin: FIDONet - The Positronium Repository (1:393/68) .