“What’s better than something that is basically a story about you?” Mr. Birnbaum said.

But that explanation ignores what many in the astro-verse consider the major turning point for Big Zodiac: The election of Donald Trump. It changed everything, according to Aliza Kelly , the astrologer-in-residence at Sanctuary. (She writes its horoscopes and conducts some of its readings.) Watching The New York Times’s forecast needle tip from Hillary Clinton to Mr. Trump raised people’s doubts about certain scientifically proven systems, Ms. Kelly said. “People became so much more receptive to the idea of there being different ways of seeing the world,” she said. They turned to astrology “in order to create some sense of structure and hope and stability in their lives.”

President Trump’s election inspired Ms. Guler to leave her work in fashion media and create Co-Star. “I was like, ‘We gotta figure out something more meaningful than what we are doing,” she said. The role social media played in the election — and how “it is changing how we operate as humans in the world” was a part of her concern, Ms. Guler said.

Investors see other trends feeding into astrology’s resurgence, Ms. Vardhana said. People are seeking smaller, specialized communities onlin e , while participation in organized religion is declining. Millennials (and the rest of us) are lonely and want community, no matter how many followers we have on social media. Why wouldn’t we turn to the stars and moons and planets and houses of the horoscope?

“This is a phenomenon and maybe astrology and the technology of Co-Star is well equipped to address it,” Ms. Vardhana said. The challenge, she said, will be converting more mainstream skeptics without “alienating the astro-nerds.”

Big Pisces Energy

A few minutes into my reading on Sanctuary’s app, Ms. Kelly, my on-demand astrologer, asked me if her assessment of my birth chart rang true. According to her interpretation, last year was a very important year for me to redefine my values. As a Libra rising, my relationships are very important to me, she noted. And in the next few weeks, I should put myself out in the world to make connections :) .

“Sure!” I typed into the app. It was just vague enough that if I did a little mental backbend, I could find examples to support her conclusions. I felt hesitant to share anything too personal about myself with a stranger until I remembered that by entering the date, city and precise time of day I was born, I had already bared my soul, astrologically speaking.