Exa Dark Sideræl Musk and Techno Mechanicus Musk (Children)
Grimes shared in her 2022 interview with Vanity Fair that she and Elon Musk had quietly expanded their family, welcoming a daughter through a surrogate.
Explaining the baby’s distinctive name, the musician said, “Exa” comes from the supercomputing term exaFLOPS, which refers to the capacity to complete 1 quintillion floating-point operations every second. “Dark,” she added, represents the unknown: something people often fear, even though it is simply “the absence of photons.” To Grimes, dark matter remains one of the universe’s most captivating mysteries.
The name Sideræl, pronounced “sigh-deer-ee-el,” was described by Grimes as a reference to “the true time of the universe” — star time, or deep-space time, rather than time as measured from Earth. She also said it pays tribute to Galadriel, her favorite character from Lord of the Rings, who famously “chooses to abdicate the ring.”
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Walter Isaacson later confirmed in his biography Elon Musk that Exa was born via surrogate in December 2021.
The book also stated that around Father’s Day 2022, the on-again, off-again couple welcomed a child named Techno Mechanicus, nicknamed Tau, also via surrogate. The biography includes a photo, dated June 2022, of Elon feeding the baby boy.
Though Grimes would prefer other salient details be kept private. “I have tried begging the public and my kids dad to keep them offline, and I’ve tried legal recourse,” she shared on social media in 2025. “The state of my children’s lives being public is of grave concern to me and I think about how to solve this every day. It’s insane to me that theres no way to deal with this.”