The Astronomy Zodiac and Your Horoscope

If you have ever read a horoscope, the astrological sign that corresponds to your birthdate probably makes some sense to you. That’s because, over time, the Sun appears to lie in front of a certain grouping of stars that is called your zodiac constellation. But there is a problem with this idea.

Astronomy doesn’t believe that the stars or constellations somehow directly influence our fate, as many astrologers have claimed. But the constellations that make up the zodiac do help us to find our way around the night sky. And that’s a good thing, because the stars are pretty amazing, and there is a lot to see in the night sky.

The 12 constellations that are traditionally grouped together into the astrological zodiac — Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces — each take up 30 degrees of the great circle that is the Sun’s annual path through the sky in front of the constellations. These are the constellations that we see in the starry night sky, and they’re all recognizable, except for Ophiuchus, which lies along the ecliptic but isn’t included in most astrological systems.

But even though these constellations are the backdrop for your horoscope, they don’t perfectly align with the Sun’s path over the course of a year. That’s because Earth rotates on its axis at an angular rate, which causes the dates of the solstices and equinoxes to drift westward relative to the backdrop stars that define each zodiac constellation. And over the long term, this shift is a bit larger than the number of days in a calendar year, such that the constellations or backdrop stars that the Sun passes through at different times of the year are not exactly the same constellations at the same time, year after year.

The astronomy zodiac has been a significant part of the history of both astrology and horoscopes. During ancient times, many people believed that the positions of the constellations in the sky could tell them about their future or provide portents for the coming year. This view no longer carries much weight with modern astronomers, but the constellations of the zodiac are still important to many amateur astronomers.

You can check out the constellations of the astronomy zodiac by looking up the ecliptic on a star map or app such as Sky Tonight. You can also test your knowledge by trying to figure out which constellation is hidden behind the Sun on your birthday. But you have to know your date of birth, because the zodiac constellation that is hidden behind the Sun on your birthday — the zodiac constellation that is your star sign — changes over time due to the effect of precession. If you want to know what constellation is behind the Sun on your birthday, use this calculator to find out. And don’t forget about Ophiuchus, which is hiding the Sun on its first 18 days in December.