The March equinox happens when the sun crosses the celestial equator – an imaginary line around the sky above Earth’s equator moving south to north.
This intersection point is sometimes called the First Point in Aries. But at this March equinox and all of those in our lifetimes, it happens when the sun is in front of the constellation Pisces. Over the long course of time, different constellations provide a backdrop to the sun as it soars above the Earth’s equator, going from south to north, year after year.
Over 2,000 years ago, the March equinox sun was in front of Aries at the time of the equinox. Now the sun is in front of Pisces, and some 600 years in the future, the March equinox sun will shine in front of the constellation Aquarius. It’s a 26,000-year cycle – Earth’s precession – that causes our vantage point on the stars to shift.
By the way, according to the mathematical wizard Jean Meeus, the March equinox sun passed out of the constellation Aries and into the constellation Pisces in 68 B.C. Not until A.D. 2597 will the March equinox sun leave the constellation Pisces and enter into the constellation Aquarius.