September 2023 Equinox Opens Spring in American Samoa and Jarvis Island

Summary: The September 2023 equinox opens spring in American Samoa and Jarvis Island but autumn in the rest of the United States.

As the only two U.S. possessions located in the Southern Hemisphere, American Samoa and equatorial Jarvis Island experience seasons oppositely from the rest of the United States; Thursday, Oct. 16, 2003, image of Jarvis Island and its daybeacon: Jo Ann Schwartz (Joann94024 at English Wikipedia), Public Domain, via Wikimedia Commons

The September 2023 equinox opens spring in American Samoa and Jarvis Island as Southern Hemisphere occupiers but autumn in the rest of the United States as Northern Hemisphere occupiers.

The second 2023 equinox occurs Saturday, Sep. 23, at 6:50 UTC, according to "2023 September equinox: All you need to know," Deborah Byrd's pre-published Saturday, Sep. 23, 2023, post on her EarthSky website. September's equinox signals astronomical autumn in the Northern Hemisphere. The Southern Hemisphere, which experiences seasons oppositely from the Northern Hemisphere, knows the September equinox as the announcer of astronomical spring.

The United States and all but two of its possessions occupy the Northern Hemisphere. Accordingly, the September equinox happens as an autumnal equinox for most of the United States.

Two components of the United States, however, do not reside in the Northern Hemisphere. American Samoa and Jarvis Island are located in the Southern Hemisphere. The two possessions, therefore, welcome the September equinox as a spring equinox. The Southern Hemisphere's September equinox and the Northern Hemisphere's March equinox are also known as a vernal (Latin: vernālis, “of or pertaining to spring; vernal," from vērnus, “of or pertaining to spring; vernal” + -ālis, relational adjective-forming suffix) equinox.

American Samoa and Jarvis Island are assigned to the UTC-11 time notation, according to the U.S. Central Intelligence Agency's chart, "Standard Time Zones of the World, February 2021," published in 2020. The UTC-11 offset indicates a lag of 11 hours behind Coordinated Universal Time (UTC), the standard that sets Earth's time zones. Accordingly, local time places the occurrence of the September equinox at 7:50 p.m., on Friday, Sep. 22, 2023, for American Samoa and Jarvis Island.

The September equinox pairs with the March equinox as Earth's two annual equinoxes. The March equinox opens astronomical spring in the Northern Hemisphere and astronomical autumn in the Southern Hemisphere.

The first 2023 equinox happened 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 astronomical autumnal opener took place 11 hours earlier for American Samoa and Jarvis Island. The South Pacific Ocean occupiers logged their autumnal equinox on Monday, March 20, 2023 at 10:24 a.m., local time.

The year's March and September equinoxes form a quartet with the year's June and December solstices. As announcers of the year's four astronomical seasons, the four events track the progress of the subsolar point on Earth's surface. The subsolar point represents the overhead placement of the solar system's Sun with respect to the Earth's surface.

Three of Earth's five circles of latitude have special significance for the year's equinoxes and solstices. The Equator and the 23rd north and south parallels, known as the Tropic of Cancer and the Tropic of Capricorn, respectively, interplay with the astronomical seasonal events.

The subsolar point's placement at the Equator represents the overhead Sun's northward passage as of the March equinox and southward equatorial crossing as of the September equinox. The subsolar point's reaches of the Tropic of Cancer on the June solstice and the Tropic of Capricorn on the December solstice signify its northernmost and southernmost extents, respectively.

American Samoa and Jarvis Island lie between the Equator and the Tropic of Capricorn. Jarvis Island nears the Equator, with coordinates of 0 degrees 23 minutes south latitude, 160 degrees 01 minutes west longitude, according to "Geographic Coordinates" listed online for "United States Pacific Island Wildlife Refuges" in the U.S. Central Intelligence Agency's reference resource, The World Factbook. American Samoa nears the Tropic of Capricorn, with coordinates of 14 degrees 20 minutes south latitude, 170 degrees 00 minutes west longitude.

The fourth and last astronomical season in 2023 occurs in December. The December solstice ushers the Northern Hemisphere's astronomical winter and the Southern Hemisphere's astronomical summer. The subsolar point's position on the Tropic of Capricorn equates to its southernmost reach.

The second of two 2023 solstices is scheduled for 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. Local times places the summer-opening solstice at 4:27 p.m. on Thursday, Dec. 21, for American Samoa and Jarvis Island.

The Jarvis Island Light, charted as daybeacon, was constructed in 1935 but has been inactive since 1942; closeup of Jarvis Island's daybeacon: Mark J. Rauzon, Public Domain, via U.S. Fish and Wildlife Service (USFWS)

Acknowledgment

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

Image credits:

As the only two U.S. possessions located in the Southern Hemisphere, American Samoa and equatorial Jarvis Island experience seasons oppositely from the rest of the United States; Thursday, Oct. 16, 2003, image of Jarvis Island and its daybeacon: Jo Ann Schwartz (Joann94024 at English Wikipedia), Public Domain, via Wikimedia Commons @ https://commons.wikimedia.org/wiki/File:Jarvis_Island_October_2003.jpg

The Jarvis Island Light, charted as daybeacon, was constructed in 1935 but has been inactive since 1942; closeup of Jarvis Island's daybeacon: Mark J. Rauzon, Public Domain, via U.S. Fish and Wildlife Service (USFWS) @ https://www.fws.gov/media/40coastguardbeacon-jarvis-markrauzon-036jpg

For further information:

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/

Central Intelligence Agency. "American Samoa: Geographic Coordinates 14 20 S, 170 00 W." The World Factbook > Countries > A > American Samoa > Geography.
Available via CIA @ https://www.cia.gov/the-world-factbook/countries/american-samoa/

Central Intelligence Agency. "Jarvis Island: 0 23 S, 160 01 W." The World Factbook > Countries > J > Jarvis Island > United States Pacific Island Wildlife Refuges > Geography > Geographic Coordinates.
Available via CIA @ https://www.cia.gov/the-world-factbook/countries/united-states-pacific-island-wildlife-refuges/#geography

Central Intelligence Agency. "Standard Time Zones of the World, February 2021." U.S. Central Intelligence Agency > The World Factbook.
Available via CIA @ https://www.cia.gov/the-world-factbook/static/31913c20666d022fa1315bd444553f8d/world_time.pdf

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. "American Samoa Has Summer Solstice As Rest of U.S. Has Winter Solstice." Earth and Space News. Wednesday, Dec. 12, 2018.
Available @ https://earth-and-space-news.blogspot.com/2018/12/american-samoa-has-summer-solstice-as.html

Marriner, Derdriu. "December Signals Summer Solstice for American Samoa and Jarvis Island." Earth and Space News. Wednesday, Dec. 18, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/12/december-signals-summer-solstice-for.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. "June Signals Winter Solstice for American Samoa and Jarvis Island." Earth and Space News. Wednesday, June 19, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/06/june-signals-winter-solstice-for.html

Marriner, Derdriu. "March Signals Autumn Equinox for American Samoa and Jarvis Island." Earth and Space News. Wednesday, March 20, 2019.
Available @ https://earth-and-space-news.blogspot.com/2019/03/march-signals-autumn-equinox-for.html

Marriner, Derdriu. "Second 2023 Equinox Happens Earth and Space News. Saturday, Sep. 23, at 6:50 UTC." Wednesday, Sep. 13, 2023.
Available @ https://earth-and-space-news.blogspot.com/2023/09/second-2023-equinox-happens-saturday.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/

Rowlett, Russ. "Line Islands Lighthouse: Jarvis Island." ibiblio > The Lighthouse Directory > Lighthouses of the Pacific and Indian Oceans, Australia, and Africa > U.S. Pacific Remote Islands > Lighthouses of the U.S. Pacific Remote Islands.
Available via ibiblio @ https://www.ibiblio.org/lighthouse/umi.htm