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The March equinox is known as the vernal equinox (or spring equinox) in the Northern Hemisphere and as the autumnal equinox (or fall equinox) in the Southern Hemisphere. [8] [7] [10] On the Gregorian calendar at 0° longitude, the northward equinox can occur as early as 19 March (which happened most recently in 1796, and will happen next in ...
The subsolar point on a planet or a moon is the point at which its Sun is perceived to be directly overhead (at the zenith); [1] that is, where the Sun's rays strike the planet exactly perpendicular to its surface. The subsolar point occurs at the location on a planet or a moon where the Sun culminates at the location's zenith. This occurs at ...
Northward equinox and southward equinox: names referring to the apparent direction of motion of the Sun. The northward equinox occurs in March when the Sun crosses the equator from south to north, and the southward equinox occurs in September when the Sun crosses the equator from north to south. These terms can be used unambiguously for other ...
The first point of Aries, also known as the cusp of Aries, is the location of the March equinox (the vernal equinox in the northern hemisphere, and the autumnal equinox in the southern), used as a reference point in celestial coordinate systems. In diagrams using such coordinate systems, it is often indicated with the symbol ♈︎.
The Met Office explains the difference between meteorological spring and astronomical spring
The March equinox point is one of the two points where the ecliptic intersects the celestial equator. Right ascension is usually measured in sidereal hours, minutes and seconds instead of degrees, a result of the method of measuring right ascensions by timing the passage of objects across the meridian as the Earth rotates .
The Sun, in its apparent motion along the ecliptic, crosses the celestial equator at these points, one from south to north, the other from north to south. [6] The crossing from south to north is known as the March equinox, also known as the first point of Aries and the ascending node of the ecliptic on the celestial equator. [10]
In astronomy, an equinox is either of two places on the celestial sphere at which the ecliptic intersects the celestial equator. [1] [2] [3] Although there are two such intersections, the equinox associated with the Sun's ascending node is used as the conventional origin of celestial coordinate systems and referred to simply as "the equinox".