What celestial marker signals the Sun's entry into the sign of Aries?

Answer

The vernal equinox

The Sun enters the sign of Aries as it crosses the vernal equinox (around March 20 or 21), marking the beginning of spring in the Northern Hemisphere.

What celestial marker signals the Sun's entry into the sign of Aries?

#Videos

The Sky Part 7: the Sun's Annual Motion - YouTube

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