AUTUMN EQUINOX! HAPPY AUTUMN EVERYONE! - 22/09/2025ย ๐๐ฅ๐๐ญ๐ฟ๐๐๐โจ๐ช
And so, a new season begins... The astronomical event known as the Autumn equinox occurs on the 22nd September. The Sun crosses the celestial equator heading South at around 19:12 BST, marking the changing of seasons here on Earth and the transition between Summer and Autumn for those of us in the Northern Hemisphere. On this day, we experience almost equal lengths of day and night. Happy Autumn Equinox, everyone! ๐
Here at Astro Dog, we're very excited about the longer, darker, starry nights that follow the Autumn equinox. We're looking forward to all of the beautiful autumnal colours, foraging in the woods, gathering around campfires, drinking hot chocolate, gazing up at the night sky and being able to get out there with our telescopes more. Plus, there is also the rest of the Aurora Borealis/Northern Lights season to look forward to! We have already seen some incredible displays this year, and the rest of the season is likely to be particularly amazing given we are still near the peak of solar maximum - a time within the Sun's 11-year solar cycle where it is most active. Exciting times!
If you would like to learn more regarding the autumnal equinox, please read on. โคย
INFORMATION ON EQUINOXES
Usually, due to the Earths tilt (of 23.5 degrees) the Northern and Southern hemispheres experience different amounts of sunlight, with one hemisphere experiencing more sunlight than the other due to it tilting towards the sun. However, there are two times every year in March and September where both hemispheres do not tilt towards or away from the sun and therefore receive equal or very close to equal amounts of sunlight.
We experience almost equal lengths of day and night during an Equinox, however due to an effect called atmospheric refraction (where the Earth's atmosphere bends the sun's light) daytime appears to last slightly longer than 12 hours.
During an equinox, the sun rises exactly due East and sets exactly due west. This is because the Earth's equator is perfectly in line with the sunโs celestial equator.
The March equinox can occur between March 19th and 21st (this year it occurred on the 20th March), the September equinox can occur between September 21st and 24th (this year it occurs on the 22nd September). Depending on the season, an equinox is called either a Spring (Vernal) or Autumn (Autumnal) equinox. In the Southern Hemisphere, these dates are reversed.
MILKY WAY CORE SEASON ENDS
The start of Autumn coincides with the end of the Milky Way core season here in the UK, as the galactic centre begins to travel beneath the horizon until it reappears again next spring. Although some landscape astrophotographers may lament the loss of the galactic centre, thereโs still plenty of wonderful night sky sights to capture images of as we head into Autumn. The bright region of the Milky Way known as the Cygnus region will still be visible for a long while, and there are also all the celestial treats of the winter constellations beginning to return to our skies.
THE AURORA SEASON BEGINS
Although we may have lost the Milky Way core, Autumn is considered by many to be the true start of the Aurora season. The much longer and darker nights of Autumn offer the perfect conditions to observe and capture photographs of the magical natural light display known as the Northern Lights.
AUTUMN EQUINOX AND GEOMAGNETIC ACTIVITY
The weeks around the Autumn and Spring equinoxes are usually the richest in geomagnetic storms. Historical records show that geomagnetic storms are twice as likely during spring and autumn compared to summer and winter. This means that Aurora hunters might be in for a special treat. We have already had many great displays this year, but letโs keep all of our fingers and toes crossed for more great Aurora displays around the equinox and as we head further into the Aurora season.๐๐๐โจ
AUTUMN EQUINOXโS CULTURAL AND RELIGIOUS SIGNIFICANCE
โข The traditional harvest festival in the United Kingdom was celebrated on the Sunday of the full moon closest to the September equinox.
โข The Jewish Sukkot usually falls on the first full moon after the Northern Hemisphere autumnal equinox, although occasionally (In the modern Jewish calendar, three times every 19 years) it will occur on the second full moon.
โข The Autumn equinox was "New Year's Day" in the French Republican Calendar, which was in use from 1793 to 1805. The French First Republic was proclaimed and the French monarchy was abolished on September 21, 1792, making the following day (the equinox day that year) the first day of the "Republican Era" in France. The start of every year was to be determined by astronomical calculations following the real Sun and not the mean Sun.
โข Neopagans observe the September equinox as a cardinal point on the Wheel of the Year called Mabon. In the Southern Hemisphere, the vernal equinox corresponds with the opposite cardinal point, Ostara.
โข The Autumn equinox marks the first day of Mehr or Libra in the Iranian calendar. It is one of the Iranian festivals called Jashne Mihragan, or the festival of sharing or love in Zoroastrianism.
โข In Japan, Autumnal Equinox Day (็งๅใฎๆฅ, Shลซbun no hi) is a public holiday. Higan (ใๅฝผๅฒธ) is a Buddhist holiday exclusively celebrated by Japanese sects during both the Spring and Autumnal Equinox.
โข In Korea, Chuseok is a major harvest festival and a three-day holiday celebrated around the Autumn Equinox.
โข The traditional East Asian calendars divide a year into 24 solar terms (่ๆฐ, literally "climatic segments"), and the autumnal equinox (Qiลซfฤn, Chinese and Japanese: ็งๅ; Korean: ์ถ๋ถ; Vietnamese: Thu phรขn) marks the middle of the autumn season. In this context, the Chinese character ๅ means "(equal) division" (within a season).
โข Doลผynki is a Slavic harvest festival. In pre-Christian times, the feast usually fell on the autumn equinox.
โข The reconstructed Cahokia Woodhenge, a large timber circle located at the Mississippian culture Cahokia archaeological site near Collinsville, Illinois, is the site of annual equinox and solstice sunrise observances.
OTHER INTERESTING EQUINOX FACTS
โข The fastest sunrises and sunsets are always at the equinoxes, no matter if you live in the Northern or Southern Hemisphere. The slowest sunsets and sunrises, on the contrary, happen around the time of the solstice. The reason for this, is that at the equinox, the Sun rises due east and sets due west, so itโs the shortest path for it to sink below the horizon.
โข At the equator, the Sun is directly overhead at noon on the days of equinoxes. If you put a vertical stick in the ground at this moment, it will cast no shadow.
โข The Earth isnโt the only planet with equinoxes โ in fact, every planet with an axial tilt experiences them.
โข There are four astronomical dates that mark the beginning of each new astronomical season. The September and the March equinoxes and the June and the December solstices.
WHAT ELSE IS THERE IN THE NIGHT SKY THROUGHOUT SEPTEMBER?
If you would like to know more about the rest of the celestial treats that can be seen throughout September, please head to our YouTube channel to watch our Night Sky Guide video for September 2025.
HAPPY AUTUMN + CLEAR SKIES!
We at Astro Dog are looking forward to Autumn and all the amazing night sky treats that arrive with the season. We are also looking forward to starting up our stargazing experience events again for another stargazing season, and we hope to welcome many more wonderful guests to our new events.
Furthermore, we hope you all have a wonderful Autumn season and enjoy the beautiful dark skies during your stargazing adventures on these longer autumn nights.
As ever, if you head out to enjoy the night sky at any point in the future we wish you good luck and clear skies. ๐