Second 2023 Equinox Happens Saturday, Sep. 23, at 6:50 UTC

Summary: The second 2023 equinox happens Saturday, Sep. 23, at 6:50 UTC as the Northern Hemisphere's autumn equinox and the Southern Hemisphere's spring equinox.

"What are you doing out in the rain?: I'm looking for the Equinox," cartoon drawing created / published between 1898 and 1915 by American illustrator, painter, lecturer and teacher Felix Mahony (1867-1939): No known restrictions on publication, via Library of Congress Photo, Print, Drawing

The second 2023 equinox happens Saturday, Sep. 23, at 6:50 UTC as opener of the Northern Hemisphere's astronomical autumn and of the Southern Hemisphere's astronomical spring, according to EarthSky's pre-published Saturday, Sep. 23, 2023, post, "2023 September equinox: All you need to know."

The September equinox's time of 6:50 UTC represents 6:50 in the morning (6:50 a.m.). As Earth's time standard, Coordinated Universal Time uses a 24-hour time notation. The UTC 24-hour clock begins at midnight, expressed as 00:00. The December equinox's UTC time equates to 1:50 a.m. Central Daylight Time (CDT), as stated in EarthSky's Sep. 23, 2023, post. CDT, which comprises the daylight savings component of North America's Central Time (CT), lags five hours behind UTC. Non-static Central Time's standard component, Central Standard Time (CST), lags six hours behind UTC.

Although time zones present different times, the September equinox actually happens at the same moment worldwide. Sidereal time, which measures time by the apparent motion of distant, fixed stars around the Earth, recognizes the September equinox as a same-moment event for everyone. Time zones assign locally relevant times that, nevertheless, translate the same, simultaneously occurring instant, as explained by Chris Deziel in "Does an Equinox Happen All Over the Earth at the Same Time?", updated April 25, 2017, on Sciencing website.

The instant of occurrence of September's equinox registers the Equator as the subsolar point on Earth, as explained in "The September Equinox," posted on the Time and Date website by Konstantin Bikos. The subsolar point references the overhead placement of the solar system's Sun with respect to Earth's surface.

The subsolar point annually journeys along a north-south axis. Earth's northern and southern 23-degree latitudinal circles mark the endpoints of the subsolar point's annual trek. Earth's two solstices emphasize the subsolar point's northernmost and southernmost reaches. The annual June solstice corresponds to the subsolar point's placement at the Northern Hemisphere's Tropic of Cancer. The December solstice relates to the subsolar point's arrival at the Southern Hemisphere's Tropic of Capricorn.

The annual pair of equinoxes announces the directional shifts in the subsolar point's annual north-south trek. The March equinox signals the subsolar point's northward crossing of the equator. Accordingly, the September equinox signals the subsolar point's southward crossing of the equator.

Earth's axial tilts during the year occasion the astronomical seasonal events termed as equinoxes and solstices. The approximately 23.4 degree angle that Earth's axis tilts with respect to the ecliptic, the imaginary plane of Earth's path around the Sun, favors the Northern Hemisphere in June and the Southern Hemisphere in December. The absence of June's northward-favoring tilt and of December's southward-favoring tilt account for the equinoctial perpendicularization of the Sun's rays across the Earth's surface.

The Saturday, Sep. 23, equinox occurs as the second and last equinox of 2023. The first of the year's two equinoxes took place Monday, March 20, at 21:24 UTC, according to Bruce McClure in "Equinox sun rises due east and sets due west," posted March 18, 2023, on the EarthSky website. The central United States experienced the event at 4:24 p.m. CDT.

The September equinox transitions to the December solstice. The year's second of two solstices will take place Friday, Dec. 22, at 3:27 UTC, according to Deborah Byrd in "2023 December solstice: All you need to know," posted June 1, 2023, on the EarthSky website. The event is set for 9:27 p.m., according to Central Standard Time (CST). The December solstice opens astronomical summer in the Southern Hemisphere and astronomical winter in the Northern Hemisphere.

The first of 2023's two solstices happened Wednesday, June 21, at 14:58 UTC, according to "2023 June solstice: All you need to know," posted New Year's Day, Jan. 1, 2023, by the Editors of EarthSky. The central United States noted the June solstice at 9:58 a.m. CDT. The June solstice marked astronomical summer in the Northern Hemisphere and astronomical winter in the Southern Hemisphere.

NOAA Satellite and Information Service's depiction of autumnal equinox of Wednesday, Sep. 23, 2015, which happened at 8:21 UTC (3:21 CDT), shows the axial configuration of Earth with respect to the Sun that allows for receipt of perpendicular sun rays across Earth's entire surface during an equinox: NOAA Satellites (NOAASatellites), Public Domain, via Flickr

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

"What are you doing out in the rain?: I'm looking for the Equinox," cartoon drawing created / published between 1898 and 1915 by American illustrator, painter, lecturer and teacher Felix Mahony (1867-1939): No known restrictions on publication, via Library of Congress Photo, Print, Drawing @ https://www.loc.gov/item/2016683289/

NOAA Satellite and Information Service's depiction of autumnal equinox of Wednesday, Sep. 23, 2015, which happened at 8:21 UTC (3:21 CDT), shows the axial configuration of Earth with respect to the Sun that allows for receipt of perpendicular sun rays across Earth's entire surface during an equinox: NOAA Satellites (NOAASatellites), Public Domain, via Flickr @ https://www.flickr.com/photos/noaasatellites/29796720246

For further information:

Bikos, Konstantin. "The September Equinox." Time and Date > Sun & Moon > September Equinox.
Available via Time and Date @ https://www.timeanddate.com/calendar/september-equinox.html

Byrd, Deborah. "2023 December solstice: All you need to know." EarthSky > Tonight > Astronomy Essentials. June 1, 2023.
Available @ https://earthsky.org/astronomy-essentials/everything-you-need-to-know-december-solstice/

Byrd, Deborah. "2023 September equinox: All you need to know." EarthSky > Tonight > Astronomy Essentials. Sep. 22, 2023.
Available @ https://earthsky.org/astronomy-essentials/everything-you-need-to-know-september-equinox/

Deziel, Chris. "Does an Equinox Happen All Over the Earth at the Same Time?" Sciencing > Science > Physics > Astronomy. Updated April 25, 2017.
Available @ https://sciencing.com/venuss-revolution-period-earth-days-2411.html

Editors of EarthSky. "2023 June solstice: All you need to know." EarthSky > Tonight > Astronomy Essentials. Jan. 21, 2023.
Available @ https://earthsky.org/astronomy-essentials/everything-you-need-to-know-june-solstice/

Mahony, Felix. "What are you doing out in the rain?: I'm looking for the Equinox." Library of Congress > Photo, Print, Drawing.
Available via Library of Congress Photo, Print, Drawing @ https://www.loc.gov/item/2016683289/

Marriner, Derdriu. "2016 Northern Autumnal Equinox Happens Thursday, Sept. 22." Earth and Space News. Wednesday, Sep. 21, 2016.
Available @ https://earth-and-space-news.blogspot.com/2016/09/2016-northern-autumnal-equinox-happens.html

Marriner, Derdriu. "2017 Autumn Equinox Happens Friday, Sept. 22, in Northern Hemisphere." Earth and Space News. Wednesday, Sep. 20, 2017.
Available @ https://earth-and-space-news.blogspot.com/2017/09/2017-autumn-equinox-happens-friday-sept.html

Marriner, Derdriu. "2018 Autumn Equinox Happens Sunday, Sept. 23, in Northern Hemisphere." Earth and Space News. Wednesday, Sep. 19, 2018.
Available @ https://earth-and-space-news.blogspot.com/2018/09/2018-autumn-equinox-happens-sunday-sept.html

Marriner, Derdriu. "2019 September Equinox Happens Sunday, Sept. 22, or Monday, Sept. 23." Earth and Space News. Wednesday, Sep. 11, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/09/2019-september-equinox-happens-sunday.html

Marriner, Derdriu. "American Samoa Has Autumn Equinox While United States Has Spring Equinox." Earth and Space News. Wednesday, March 1, 2017.
Available @ https://earth-and-space-news.blogspot.com/2017/03/american-samoa-has-autumn-equinox-while.html

Marriner, Derdriu. "Autumnal Equinox 2015 in Northern Hemisphere on Wednesday, Sept. 23." Earth and Space News. Tuesday, Sep. 22, 2015.
Available @ https://earth-and-space-news.blogspot.com/2015/09/autumnal-equinox-2015-in-northern.html

Marriner, Derdriu. "First 2023 Solstice Happens Wednesday, June 21, at 14:58 UTC." Earth and Space News. Wednesday, June 7, 2023.
Available @ https://earth-and-space-news.blogspot.com/2023/06/first-2023-solstice-happens-wednesday.html

Marriner, Derdriu. "June 21, 2023, Solstice Is Wintry for American Samoa and Jarvis Island." Earth and Space News. Wednesday, June 14, 2023.
Available @ https://earth-and-space-news.blogspot.com/2023/06/june-21-2023-solstice-is-wintry-for.html

Marriner, Derdriu. "March 20 Equinox Opens 2020 Lineup of Two Equinoxes and Two Solstices." Earth and Space News. Wednesday, March 18, 2020.
Available @ https://earth-and-space-news.blogspot.com/2020/03/march-20-equinox-opens-2020-lineup-of.html

Marriner, Derdriu. "Moon Reaches June Apogee 27 Hours After June 21, 2023, Solstice." Earth and Space News. Wednesday, June 21, 2023.
Available @ https://earth-and-space-news.blogspot.com/2023/06/moon-reaches-june-apogee-27-hours-after.html

Marriner, Derdriu. "September Signals Spring Equinox for American Samoa and Jarvis Island." Earth and Space News. Wednesday, Sep. 18, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/09/september-signals-spring-equinox-for.html

McClure, Bruce. "Equinox sun rises due east and sets due west." EarthSky > Tonight. March 18, 2023.
Available @ https://earthsky.org/tonight/equinox-sun-rises-due-east-and-sets-due-west/

NASA Scientific Visualization Studio. "Moon Phases 2023." NASA Solar System Exploration > Resources.
Available via NASA Solar System Exploration @ https://solarsystem.nasa.gov/resources/2785/moon-phases-2023/

National Oceanic and Atmospheric Administration. "Changing seasons." National Oceanic and Atmospheric Administration > Education > Resource collections > Climate.
Available @ https://www.noaa.gov/education/resource-collections/climate/changing-seasons

Whitt, Kelly Kizer. "Cosmic trio on June solstice 2023. Best photos." EarthSky > Tonight. June 21, 2023.
Available @ https://earthsky.org/tonight/solstice-sky-cosmic-trio-moon-venus-mars/#:~:text=The%20solstice%20arrived%20on%20June,the%20evening%20of%20the%20solstice.