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Elon Musk and Grimes Welcome New Baby Girl, Y

The baby's full name is Exa Dark Sideræl Musk. Here's how to pronounce it.

Meara Isenberg Writer
Meara covers streaming service news for CNET. She recently graduated from the University of Texas at Austin, where she wrote for her college newspaper, The Daily Texan, as well as for state and local magazines. When she's not writing, she likes to dote over her cat, sip black coffee and try out new horror movies.
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Meara Isenberg
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Elon Musk and Grimes

Grimes said in a tweet Thursday that she and Musk have split.

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Grimes and Elon Musk secretly welcomed a new baby girl, Y, via surrogate in December. A Vanity Fair profile of the musician published Thursday broke the news. The full name of the child, the pair's second, is Exa Dark Sideræl Musk.

According to the article, Grimes acknowledged the baby after the Vanity Fair interviewer heard an infant crying in her Austin, Texas, home. She said that her relationship with Tesla and SpaceX boss Musk was "very fluid," but also that she'd probably refer to him as her boyfriend. Later on Thursday, however, Grimes tweeted that she and Musk have split since the article was written. 

"Me and E have broken up again since the writing of this article haha, but he's my best friend and the love of my life, and my life and art are forever dedicated to The Mission now, I think Devin wrote that part of the story rly well," Grimes wrote on Twitter. "Sique - peace out."

The couple appeared to break up in 2021. Musk told Time magazine that he and Grimes were "probably semi-separated."

Grimes also provided a breakdown of her daughter's full name, Exa Dark Sideræl Musk.

"Exa" references "the supercomputing term exaFLOPS (the ability to perform 1 quintillion floating-point operations per second)," according to Vanity Fair. She also said Dark is "the unknown. People fear it but truly it's the absence of photons. Dark matter is the beautiful mystery of our universe." Sideræl, pronounced "sigh-deer-ee-el," is "a more elven" spelling of sidereal, Grimes told Vanity Fair, "the true time of the universe, star time, deep space time, not our relative earth time." It's also reportedly a nod to the musician's favorite Lord of the Rings character, Galadriel.

Grimes and Musk had their first child, X, in May 2020. His full name is X Æ A-12, and Grimes pronounces it as "X A.I. Archangel," according to Vanity Fair. In the interview, Grimes said that she and Musk planned to have more children.

Representatives for Grimes didn't immediately respond to a request for comment.