An astronomer contemplates the equinox

earthsky.org | 9/21/2019 | Guy Ottewell
Click For Photo: https://en.es-static.us/upl/2019/09/solar-system-9-22-2019-ottewell-300x120.png

View larger. | This view is about 7 hours before the instant of the September 23 equinox. Image via Guy Ottewell’s blog.

Originally published at Guy Ottewell’s blog. Re-printed here with permission.

September - Equinox - Monday - September - O'clock

The September equinox falls on Monday September 23, 2019 at about 8 o’clock by Universal Time. That is after sunrise for Europe, but by American clocks, it’s nearer to the midnight between Sunday and Monday. So the good time to contemplate equinoxes is on Sunday evening.

The chart at top shows the view only about 7 hours before the instant of the equinox (September 23, 2019 at 07:50 UTC).

Sun - Places - Sun - Path - Sky

The sun is arriving at one of the two places where the ecliptic (sun’s path on our sky’s dome) crosses the celestial equator (imaginary line above Earth’s equartor). In other words, the sun is moving into the southern celestial hemisphere. At the opposite crossroads in the sky – 180 degrees away on the sky’s dome – we show an imaginary anti-sun, toward which the shadow of our Earth points.

And halfway between them is the antapex of Earth’s way, the point away from which we are moving in our orbit.

Jupiter - Saturn - Time - Orbit - Sun

Near this are Jupiter and Saturn, because at this time we are rushing away from them in orbit around the sun. Earth passed between the sun and each of these planets in the summer. Jupiter appeared exactly 90° from the sun (east quadrature) on September 8, and the antapex will reach Saturn on October 7.

Click For Photo: https://en.es-static.us/upl/2019/09/solar-system-9-22-2019-ottewell-lg.png | This 3-dimensional picture shows the planets’ orbits and their paths in the month of September, with sight-lines from Earth to the sun and planets at September 23, 2019....
(Excerpt) Read more at: earthsky.org
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