Vernal Equinox 2024 Edt. The vernal equinox — is an astronomical phenomenon when the sun, in its visible motion along the ecliptic, crosses the celestial equator. But why does this particular day signify the onset of.

Late last night (march 19) was the march equinox, an annual astronomical event that marks the change of seasons across the globe. For those of us in the northern hemisphere, this was marked by the arrival of the vernal equinox.