How to determine the position of vernal equinox? When is the vernal equinox?

How to determine the position of vernal equinox? When is the vernal equinox?

The vernal equinox runs on the celestial sphere at a speed of 0.8' every year. The vernal equinox was located in Aries 2000 years ago. This is the origin of the symbol of the vernal equinox, just like the symbol of Aries in the zodiac 12. Later, the spring equinox passed Pisces, and now it is in Aquarius.

In order to facilitate discussion, the vernal equinox at a certain reference moment is often defined in astronomy and aerospace, such as the average vernal equinox at the beginning of 1950. The meaning of short-period nutation is removed on average here. So the vernal equinox is fixed.