In series like Planetary, of which he was a creator, and Astonishing X-Men, his drawings conveyed a sense of realism in situations that were often fantastical.

John Cassaday, an award-winning comic book artist best known for his runs on Planetary, a series he helped create about a trio of adventurers investigating strange events, and Astonishing X-Men, on which his work offered readers a new entry point to a decades-old franchise, died on Sept. 9 in Manhattan. He was 52.

Tara A. Martinez, his partner, said he died of cardiac arrest in a hospital.

In a medium known for its often fantastical scenarios, Mr. Cassaday’s drawings conveyed a sense of realism. Nowhere was that more evident than in his work on Planetary, which he created with the writer Warren Ellis. His work on that series “rightfully put him on the map,” Mark Waid, a comic book editor and writer, wrote on Facebook.

Writing in his

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