Frozen and lonely, Planet X circled the far reaches of the solar system awaiting discovery and a name. It got one thanks to an 11-year-old British girl named Venetia Burney, an enthusiast of the planets and classical myth.

On March 14, 1930, the day newspapers reported that the long-suspected “trans-Neptunian body” had been photographed for the first time, she proposed to her well-connected grandfather that it be named Pluto, after the Roman god of the underworld.

And so it was.

Venetia Phair, as she became by marriage, died April 30 in her home in Banstead, in the county of Surrey, England. She was 90. The death was confirmed by her son, Patrick.

Venetia, on the fateful day that Pluto popped into her head, was having breakfast with her mother and her grandfather, Falconer Madan, retired librarian of the Bodleian Library at Oxford. He had exciting news to tell. Scientists at the Lowell Observatory in Flagstaff, Ariz., had just photographed a planet lying beyond Neptune. Its existence had been postulated since the late 19th century, and astronomers working under Percival Lowell, the observatory’s founder, had been chasing it photographically since 1906. Now theory had become fact.