Sun enters Gemini on June 21
Solstice sun on Taurus-Gemini border
The June solstice arrives on June 21 at 3:32 UTC. At that moment, the sun is in front of the constellation Taurus the Bull. About 1/2 day later – on June 21 at around 15 hours UTC – the sun crosses a constellation bounary. It moves out of the constellation Taurus and into the constellation Gemini the Twins.
So the solstice sun shines very close to the Taurus-Gemini border.
And, when we say the sun is “in” this or that constellation, we only mean the sun appears in front of that constellation along our line of sight.
Sun enters Gemini
Because of a motion of Earth called precession, the sun is always moving along the zodiac. The cycle of this movement is 26,000 years long. The sun’s movement is toward the west. Thus, relative to the zodiac’s backdrop of stars, the sun on every solstice appears a bit westward of the previous year’s solstice sun.
Thirty-two years ago, in the year 1989, the sun was in front of the constellation Gemini on the day of the June solstice. It was on the western edge of the constellation, nearly in Taurus (which is west of Gemini).
But then the sun moved westward … and in the following year, 1990, the sun did indeed shine in front of Taurus at the solstice.
There are 12 constellations of the zodiac. And the cycle lasts 26,000 years. So you might see that the sun will continue to shine in front of Taurus at the June solstice for many, many years. It won’t cross a constellation boundary again until the year 4609. That’s when the June solstice sun will finally move into the constellation Aries, the constellation to the immediate west of Taurus.
Signs versus constellations
Thus, astrologically speaking, the sun occupies the first point of (the sign) Cancer on the June solstice, irrespective of which constellation lies behind the sun in the sky at this time.
Also, astrologically, the sun reaches the first point of (the sign) Leo when it resides 30 degrees east of the June solstice point along the ecliptic – regardless of which constellation lies behind the sun.
On the other hand, the solstice and equinox points slowly but surely move westward relative to the zodiacal constellations.
The solstice and equinox points go full circle through the constellations of the zodiac in about 26,000 years.
Bottom line: On June 21, 2021, at around 15 UTC, the sun moves out of the constellation Taurus the Bull and into Gemini the Twins.