Sun and Calendar · 8 of 9

The Wandering Equinox

When does the Age of Aquarius actually begin?

The point the whole sky is measured from is sliding out of Pisces. When it reaches Aquarius, and why the zodiac signs no longer match the stars.

You’ll be able to explain why the zodiac signs no longer match the stars behind the Sun.

12 steps · about 9 min

Before this: Why the Sky Moves (8 min), Celestial Coordinates (8 min), The Ecliptic (8 min)

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← GUIDES

Born 21 March to 19 April? Your sign is Aries, but the Sun was in Pisces. The sign starts here, at the March equinox, where the ecliptic, the Sun's path, crosses the celestial equator. No star marks it, and the stars have moved on.

You met this point as RA 0h: every star's right ascension counts east from it. To find it, drop 16°, a fist and a half, from Algenib, roughly south.

The point does not stay put. Run 68 BC to AD 2597 with the stars held still: the equator swings, and the crossing slides west down the drawn track, 1° every 72 years, about a lifetime, once round in 25,772.

Why: Earth's axis wobbles like a top, and its pole walks this ring, from Thuban to Polaris and on to Vega. The celestial equator is the circle 90° from the pole, so it tips with it, and its crossing with the ecliptic slides.

Look back. From about 1865 BC the equinox lay in Aries, the Ram of Hamal and Sheratan — why it is still called the First Point of Aries. It crossed the drawn boundary into Pisces in 68 BC, the measured 29° ago.

Forward, the equinox has the measured 8.0° of Pisces left. At 50.3″ a year that is about 570 years: it crosses into Aquarius in 2597 (Jean Meeus's figure). By the IAU's boundaries, that is the Age of Aquarius.

Astrologers do not all wait for 2597. An astrological age is usually an equal 30° slice of the ecliptic, the ticks, not the IAU's 1930 boundaries: Aquarius holds 24° of the line, Pisces 37°. So their dates differ by centuries.

The sign of Aries starts at the equinox and runs 30° east. The constellation starts about 29° along. In 2026 the Sun passed the equinox on 20 March, in Pisces, and reached Aries on 19 April — just as the sign of Aries ended.

Neither side is wrong. The signs are tied to the seasons — Aries is the month after the March equinox, wherever the stars are — and the constellations to the stars. They lined up two thousand years ago, have slid a sign apart since, and line up again about 24,000 years from now.

Six thousand years on one page: the March equinox's place along the ecliptic, across the constellations' uneven stretches; the marks are where it changes constellation. Signs follow the seasons; constellations follow the stars.

Your turn. Drag to your birthday. The outlined patch the Sun stands in is the constellation it was really in; most likely the one before your sign.

The March equinox, 68 BC to 2597. The stars behind your birthday Sun have slid about a sign.

The equinox slides west, 1° in 72 years
Pisces since 68 BC; Aquarius in 2597
Signs follow seasons; constellations, stars

The Wandering Equinox

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