Moonrise, downstate New York, March 12, 2025
The Vernal Equinox, the Astronomical beginning of spring, occurs this year on Thursday, March 20, 2025 at 5:01 AM EDT (9:01 UTC, March 20, 2025).
What’s so special about this event?
- 12 equal hours of daylight and darkness everywhere on the planet.
- The beginning of Astronomical Autumn for our friends in the Southern Hemisphere
- The sun rises due east and sets due west at any point on the planet
- The sun’s elevation above the nearest horizon (southern horizon for Northern Hemisphere observers and northern horizon for Southern Hemisphere observers) is exactly equal to the compliment of their latitude. For example, if your latitude is +40 (40 degrees north latitude), the elevation of the sun would be 50 degrees above the southern horizon.
- At the Vernal (March) and Autumnal (September) equinox, the sun is directly above Earth’s equator.
The Earth’s Orbit
The Earth orbits the sun in a specific equatorial plane known as the “Plane of the Ecliptic” and the sun traces an imaginary line on the sky as it appears to move from east to west. This apparent motion of the sun is caused by the Earth’s west to east (counterclockwise) rotation. As inhabitants of the surface, this translates into an apparent motion of the sun across the sky. The imaginary line traced out by the sun is known simply as the “Ecliptic”.
Another aspect of the Celestial Coordinate system that plays a key role is the “Celestial Equator”, the projection of the Earth’s Equator onto the sky. This imaginary line has a Declination (celestial latitude) of 0, just like the actual equator on the earth. This is the key factor that provides for due east-west rising and setting of the sun and equal hours of daylight and darkness.
At the Vernal (March/Spring) and Autumnal (September) equinoxes, the sun is directly above Earth’s equator.
What does the “Astronomical Beginning of Spring” actually mean?
The Astronomical Beginning of Spring is a convention, marking the first point since the beginning of the New Year (January 1st) when the sun, seemingly traveling along the Ecliptic, crosses the Celestial equator.
In addition and like the Vernal Equinox, the Astronomical Beginning of Autumn occurs on or near September 21 of each year and marks the 2nd and last time after the New Year when there are equal hours of daylight and darkness.
Note: the word equinox derives from the Latin words for “equal night”: aequus (equal) and nox (night).
Major Planets
Along with the prominent constellations of winter that include Orion, Taurus and Gemini, mighty Jupiter is high overhead during the evening hours of March 19 and is flanked to the southwest by Aldebaran, the right eye of Taurus the bull (see our video of the Night Sky for the 2nd week in March). Venus, Mercury and Saturn are too close to the sun to observe and rise with it. Along with the waning gibbous moon and the majestic galactic center, the prominent constellations of summer, Sagittarius and Scorpio, are prominently placed on the Meridian in the predawn hours of March 20.
The prominent constellations of summer, Sagittarius and Scorpio, along with the waning gibbous moon flanking the red supergiant star Antares to the west, we see the majestic Galactic Center front and center, 25,000 light years distant. Image via Stellarium (v 24.4).
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A quick, interactive web-based version of Stellarium is available here Tonight's Sky. When you launch the application, it defaults to north-facing and your location (on mobile and desktop).
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