Did NASA change your star sign? Ophiuchus, precession and why your sign still stands

What the Stylist article claimed

Stylist’s piece, headlined “Astrology fans, you’ve been reading the wrong star sign all this time”, was first published in 2016 and last updated on 1 February 2023. It says that “Nasa has added a brand new zodiac sign into the mix”, that 86% of people were born under a different constellation from their star sign, and it ends with a table of “correct dates” for thirteen signs, with Ophiuchus running from 29 November to 17 December.

The source behind it is real. NASA Space Place, a science site for children, had a page called Constellations and the Calendar, last updated in January 2016. It explained that the Babylonians divided the zodiac into twelve equal parts, that the sky has shifted since then because Earth’s axis no longer points in quite the same direction, and that the Sun also lines up with Ophiuchus for about 18 days a year. The page opened with a plain line: “Astrology is something else. It’s not science.” Its subject was the difference between astronomy and astrology, not a new set of signs.

When the story spread in September 2016, NASA answered on its official Tumblr: “We didn’t change any zodiac signs, we just did the math.” Nothing since has changed that. NASA describes where the Sun appears against the stars. It does not assign signs, and astrology has no governing body that could adopt a new one.

Where the story lands

Some of it is right. Precession is real, the Sun does pass through Ophiuchus every year, and the astrologer Stylist interviewed, Pauline Gerosa, correctly says that Ophiuchus “has always been one of the constellations that fall along the ecliptic”. The article also repeats NASA’s reminder that no one has shown astrology can predict the future.

The headline claim is wrong. NASA did not add a sign, and nothing was newly revealed. The shift was described by the Greek astronomer Hipparchus around 130 BC, and the NASA page was more than four years old by the time of Stylist’s July 2020 update.

The table is mislabelled. Its dates are the days the Sun crosses the borders of the constellations, using boundaries the International Astronomical Union approved in 1928 and published in 1930. They are astronomy, not the sign dates of any astrological system. They also move from year to year: our check with Astronomy Engine, the library behind this site’s charts, puts the Sun in Ophiuchus from 30 November to 18 December in 2026, a day later than the table.

The 86% figure has no source in the article. Our own count found that on about 89% of days in 2026 the constellation behind the Sun differs from the tropical sign, so the broad point holds: most birthdays fall in a different constellation. But that is a statement about constellations. It would only make your sign wrong if signs were constellations, and in Western astrology they are not.

Two smaller points. Stylist says the Babylonians invented the twelve signs “almost 3,000 years ago”, echoing NASA’s round figure, while Britannica dates the division into twelve equal 30-degree signs to about 500 BC, roughly 2,500 years ago. And the personality profile given for Ophiuchus, as a healer and an interpreter of dreams, comes without a source; none of the material Stylist cites describes it.

What precession is

Earth spins like a slightly tilted top. The pull of the Sun and Moon on its bulging equator makes the axis trace a slow circle, which NASA puts at about 25,770 years for one full turn. That is roughly one degree every 72 years, or about 50 arcseconds a year.

As the axis turns, the point where the Sun sits at the March equinox slides backwards through the zodiac constellations. Since about 500 BC it has moved around 35 degrees, more than one whole sign. That is why a birthday that once had the Sun in front of the stars of Leo now has it in front of Cancer. NASA used a 4 August birthday as its example, and our calculation agrees.

Why tropical astrology follows the seasons

Western astrology mostly uses the tropical zodiac. As the Swiss Ephemeris documentation puts it, 0 degrees Aries is fixed at the vernal point, where the Sun sits at the March equinox. The circle is then divided into twelve equal 30-degree signs, so Aries begins with northern spring, Cancer at the June solstice, Libra at the September equinox and Capricorn at the December solstice.

Because the signs are tied to the equinoxes, precession does not move them. It moves the constellations relative to the signs. The two share names because they roughly lined up when the system took shape, but they have been separate measurements for a very long time. Tropical astrology is a calendar of the seasons expressed in twelve symbols, not a claim about which stars sit behind the Sun.

Sidereal astrology, used in Indian Vedic astrology and by some Western astrologers, anchors the signs to the stars instead. The Swiss Ephemeris documentation notes that the two zodiacs nearly coincided 1,500 to 2,000 years ago and now differ by more than 20 degrees, and that sidereal astrologers disagree about the exact starting point. Even so, sidereal astrology keeps twelve equal signs. Neither system uses the unequal constellation dates in Stylist’s table, and neither has a sign called Ophiuchus.

What Ophiuchus means for you

Ophiuchus, the serpent bearer, is one of the 88 constellations the IAU recognises. Its southern part reaches down to the ecliptic, the Sun’s yearly path, between Scorpius and Sagittarius. NASA’s page says the Babylonians knew of thirteen constellations along that path and left one out so that each month had an equal slice. The exact 18-day crossing comes from the modern boundaries.

If you were born between about 29 November and 18 December, the Sun was in front of the stars of Ophiuchus. In tropical astrology you are a Sagittarius, as you always were. In the common sidereal systems, which sit more than 20 degrees behind the tropical signs, you would be a Scorpio or an early Sagittarius.

That leaves room for something useful. If the image of a figure holding a serpent speaks to you, treat it as a symbol you choose to reflect on, not a correction to your chart. Your Sun sign is one placement among many. Your Moon and rising sign need a birth time and place, and they often say more about everyday temperament than the Sun alone.

To check your tropical sign, use the zodiac sign calculator. If you were born on a day when the Sun changes sign, add your time and place in the birth chart calculator. Unified Reading uses the tropical zodiac throughout, and the method page lists its conventions and sources.