Why Your Zodiac Sign Might Not Match the Stars
Earth's slow wobble means the Sun is no longer in the constellation your sign is named after on most birthdays. Here's why, and what astrologers say.
Every few years a headline announces that the zodiac has changed and you might have a new sign. The story behind it is real astronomy, and it's more interesting than the headlines.
How the zodiac was drawn
More than 2,000 years ago, astronomers in Babylon and later Greece tracked the path the Sun appears to take across the sky over a year. They divided that path into 12 equal sections of 30 degrees, each named after a constellation along the way. Your sign was the section the Sun was in on the day you were born.
Earth's slow wobble
Earth spins like a slightly wobbly top. Its axis traces a slow circle in space, a motion called precession, which takes about 26,000 years to complete. Over the centuries since the zodiac was drawn, this has shifted the background of stars by almost a whole sign. On most birthdays today, the Sun is actually in front of the constellation before the one that gives the sign its name.
What about Ophiuchus?
The constellations aren't equal in size, either. Astronomers today use official constellation borders agreed in 1930, and by those borders the Sun also passes through a 13th constellation, Ophiuchus, the Serpent Bearer, from about November 29 to December 17. It spends as little as about a week in front of Scorpius and around six weeks in front of Virgo.
When NASA explained this in a 2016 article for students, it went viral as "NASA changed the zodiac." NASA hadn't changed anything; it was describing the sky.
What astrologers say
Most Western astrologers use the "tropical" zodiac, which is tied to the seasons, not the stars: Aries always begins at the spring equinox. In that system, the signs are fixed sections of the year, so precession doesn't change anyone's sign. Some astrologers, especially in India, use a "sidereal" zodiac that follows the constellations, which is why their dates differ.
Astrology isn't a science, but the zodiac is a fun way to talk about personality, and a great excuse to look up at the sky. Find your sign on our zodiac guide or check your compatibility.