NASA: "We didn't change any Zodiac signs. We just did the math."

NASA is causing some panic for those who follow astrology, but they would like everyone to chill out.

WASHINGTON (NBC NEWS) - NASA is causing some panic for those who follow astrology.

They announced a 13th Zodiac sign, which means if you were an Aries, you could be a Pisces. But don't panic!

NASA says there have always been 13 constellations. Ancient Babylonians chose only 12 to fit their calendar - leaving out Ophiuchus (which is a good thing too, since no one could figure out how to pronounce it.)

Over the centuries, the earth has shifted, so the Zodiac signs aren't even what we all go by anyway.

The bottom line is this: officials at NASA say they study astronomy, not astrology. (And NASA points out that astrology is not science.) So if someone asks you your sign, just go by what you always have.

NASA wrote on its Tumblr page: "Astronomy is the scientific study of everything in outer space. Astronomers and other scientists know that stars many light years away have no effect on the ordinary activities of humans on Earth. Astrology is something else. It's not science. No one has shown that astrology can be used to predict the future or describe what people are like based on their birth dates."

NASA adds:

When the Babylonians first invented the 12 signs of zodiac, a birthday between about July 23 and August 22 meant being born under the constellation Leo. Now, 3,000 years later, the sky has shifted because Earth's axis (North Pole) doesn't point in quite the same direction.

The constellations are different sizes and shapes, so the sun spends different lengths of time lined up with each one. The line from Earth through the sun points to Virgo for 45 days, but it points to Scorpius for only 7 days. To make a tidy match with their 12-month calendar, the Babylonians ignored the fact that the sun actually moves through 13 constellations, not 12. Then they assigned each of those 12 constellations equal amounts of time.