Sofia Whitcombe began her day with the startling realization that she might not be exactly who she thought she was.

“My whole life, I thought I was a Capricorn,” the 25-year-old publicist said. “Now I’m a Sagittarius? I don’t feel like a Sagittarius!” It felt, she said, like a rug had been pulled from under her feet.

“Will my personality change?” she mused. “Capricorns are diligent and regimented, and super-hard-working like me. Sagittarians are more laid back. This is all a little off-putting.”

Countless people reacted on social networks Friday to the “news” that the stars have shifted alignment, astrologically speaking. No matter that the astronomy instructor who started it all in a weekend newspaper interview said it was an old story — very old; 2,000 years old, actually — and that astrologists were insisting it wouldn’t change a thing. The story had traveled around the blogosphere like, well, a shooting star.

Some people seemed angry. “I believe it’s a zodiac scam,” said Jose Arce, a 38-year-old from Fort Lee, N.J., who runs a body shop. “I’ve known myself to be a Sagittarius, I believe, since I was born. So to come up now with some new sign? It’s unacceptable!”

But others weren’t so ready to curse the stars. Kathy Torpey always felt like she was “a Scorpio trapped in a Sagittarian body” — emotional and creative, she said, more than competitive and intellectual like Sagittarians.

So on Friday, even though she pays little heed to horoscopes, Torpey said she was thrilled to discover that she may have always been a Scorpio, after all.

“You have no idea what relief and joy I felt after hearing the wonderful news of the zodiac changes,” wrote the 43-year-old mother of two from Willow Grove, Pa., in an e-mail, tongue-in-cheek to be sure. “Up until now, I felt like my whole life has been a lie!”

Astrologers across the country reported a wave of calls, e-mails or website hits from concerned clients. “People are more attached and loyal to their signs than they thought,” said Eric Francis, editor of PlanetWaves.net, who said he had had 25,000 hits on his site since midnight. “It’s interesting how many people are panicking their sign is wrong.”

Astounded by all the kerfuffle was the man who started it, astronomy instructor Parke Kunkle.

In an interview Sunday in the Star Tribune of Minneapolis, Kunkle had explained that the Earth’s wobbly orbit means it’s no longer aligned to the stars in the same way as when the signs of the zodiac were first conceived, about 5,000 years ago. That means, Kunkle said, that when astrologers say the sun is in Pisces, it’s really in Aquarius, and so on.

“Astronomers have known about this since about 130 B.C.,” Kunkle told The Associated Press Friday in his office at the Minneapolis Community and Technical College, his phone ringing constantly, as it had since the article came out. (One person had even demanded: “Give me my sign back.”)

“This is not new news. Almost every astronomy class talks about it.”

New news or old, most people had never heard it before. And one of the more fascinating elements of the story was talk of a new sign altogether.

By the reckoning of Kunkle and other astronomers, astrologers are not only a month off in their zodiac signs, but they are neglecting a 13th constellation, Ophiuchus (Ooh-FEE-yew-kus) the Serpent Bearer, for those born from Nov. 30 to Dec. 17.

According to myth, Ophiuchus became a healer when he killed a snake and another appeared with an herb in his mouth that revived the dead one, said Amy Sayle, an astronomy educator at the Moorehead Planetarium at the University of North Carolina, Chapel Hill.

Mary-Iris Taylor, a writer in St. Louis, had seen the story of Kunkle’s zodiac on TV, but on Friday, she read a link a friend had posted on Facebook and realized she was an Ophiuchus.

And what, she wondered, did that mean?

“I’d just like to know what I’m supposed to be like now,” she said. “As a Sagittarius, I was supposed to be the life of the party — at least, that’s what I wanted it to mean,” she laughed. “Now what?”

According to many astrologists, she shouldn’t worry.

Linda Zlotnick, an astrologer for 32 years in St. Paul, Minn., said she and fellow astrologers have long known of the issue raised by Kunkle, but that the most commonly used zodiac — tropical — isn’t affected by it. Zlotnick said the sidereal zodiac, which isn’t as widely used, IS based on the constellations.