A resurfaced NASA blog has claimed there are actually 13 zodiac signs - not 12.
The extra sign - known as Ophiuchus - is supposedly the horoscope for those born between 29 November and 17 December.
As a constellation Ophiuchus is a snake bearer, and he is said to have been the first doctor.
If Ophiuchus was in use as an official star sign, it would change the dates for horoscopes for the rest of the year.
This means some people might find their birthday fell under a different sign.
What is my star sign?
Ophiuchus is not an official sign of the zodiac, so your star sign has not changed.
However, if it were included, these would be the dates:
Capricorn – January 20 to February 16
Aquarius – February 16 to March 11
Pisces – March 11 to April 18
Aries – April 18 to May 13
Taurus - May 13 to June 21
Gemini – June 21 to July 20
Cancer – July 20 to August 10
Leo – August 10 to September 16
Virgo - September 16 to October 30
Libra – October 30 to November 23
Scorpio – November 23 to November 29
Ophiuchus – November 29 to December 17
Sagittarius – December 17 to January 20
In a 2016 blog post, NASA explained how the ancient Babylonians divided the zodiac into 12 equal parts, choosing one constellation for each.
But there were actually 13 constellations in the zodiac, so they chose one - Ophiuchus - to leave out.
The news of a possible 13th star sign caused uproar among astrology fans, with many worrying they'd been reading the wrong horoscope.
But as astrologer Susan Miller told Elle: "The ancients discussed whether or not to include a 13th sign — they debated, they did empirical studies, and in the end, they felt it was not significant.
"Remember, they invented astrology and we have to go with what they gave us."
Writing for New Scientist, Phil Plait also explained "by some counts, there are as many as 21 zodiacal constellations."
