On March 14, 1930, 11-year-old Venetia Burney and her family were eating breakfast at their home in Oxford, England, discussing the biggest news of the day: The discovery of a new planet. Venetia's grandfather, Falconer Madan, retired head Librarian of the Bodleian Library at the University of Oxford, read to her from page 14 of The London Times:

NEW PLANET: DISCOVERY BY LOWELL OBSERVATORY

Professor Harlow Shapley, Director of the Harvard Observatory, announced today that the Lowell Observatory at Flag-staff, Arizona, had discovered a ninth major planet. The planet, which has not yet been named, is beyond Neptune. It is probably larger than the Earth, but smaller than Uranus. The discovery confirms the belief of the late Dr. Percival Lowell that such a planet existed and was in fact the result of a systematic search of several years in support of Dr. Lowell’s belief. Professor Shapley calls the discovery the most important since the discovery of Neptune in 1846.

Venetia was well familiar with Greek and Roman mythology, and further had recently been acquainted with the planets and their relative distances from the Sun during a nature-walk lesson at school. As the family discussed what the new planet should be named, she said, “I think Pluto would be a good name for it.” Pluto is the god of the underworld, who could make himself invisible and dwelt in a place that sunlight didn’t reach. It seemed a fitting name for a dark, remote planet.

Her grandfather immediately suggested the name to a friend of his, Herbert Hall Turner, professor of astronomy at the University of Oxford, who was attending a meeting of the Royal Astronomical Society (RAS) in London at the time. There was already a heated debate in Flagstaff and at the RAS meeting about what to call the new planet, but nobody involved had thought of Pluto.

“I think PLUTO excellent!!" Turner wrote back. "We did not manage to think of anything so good at the RAS yesterday. The only at all meritorious suggestion was Kronos, but that won’t do alongside Saturn.” (The Greek equivalent of Saturn is Kronos.)

Turner then sent a telegram to the Lowell Observatory in Flagstaff stating:

Naming new planet, please consider PLUTO, suggested by small girl Venetia Burney for dark and gloomy planet.

At the time at the Lowell Observatory, the leading candidates were Minerva, Zeus, Atlas, and Persephone. When they heard Pluto, many loved it: Not only was the name fitting from a mythological standpoint, but Pluto also started with PL, which would be in homage to Percival Lowell, who had played an integral role in the search for “Planet X,” the predicted ninth planet of the solar system based on irregularities in the orbit of Uranus that could not wholly be accounted for by Neptune. Lowell died 14 years before Pluto would be discovered. (Their estimates of the mass of Neptune were incorrect; Planet X did not actually exist, at least as far as Lowell defined it.)

When it finally came to a vote as to what to officially name the newly discovered planet, it was unanimous, and Venetia became the second person in her family to name a celestial body. (Her great uncle, Science Master of Eton Henry Madan, in 1877 suggested the name for the two dwarf moons of Mars, Deimos and Phobos.)

While Venetia is often credited as being very clever in her choice of Pluto—taking into account the subtle connections between the unnamed planet and the god of the underworld—she doesn’t remember giving it that much thought. “Whether I thought about a dark, gloomy Hades, I’m not sure,” she said in an interview with NASA in 2006. “I can still visualize the table and the room, but I can remember very little about the conversation.”

Still, Venetia's grandfather, shortly after the event and presumably with a slightly more accurate account given it was fresh in his mind, certainly credited her with giving it a fair amount of rational thought. So much so that he wrote a “Thank You” letter to her teacher, K.M. Claxton, shortly after the name was chosen:

I really believe that had Venetia been under a less capable and enlightened teacher than yourself, the suggestion of Pluto would not have occurred to her, or, if made, would have been just a vague guess. As it is, her acquaintance with some of the old legends of Greek and Roman deities and heroes, and that ‘nature walk’ in the University Parks, by which she was taught the relative spaces between the Planets and the Sun, and the gloom of distance, enabled her to grasp at once the special elements of the situation, and to be the first to make a suggestion so reasonable as to be accepted (it appears) by the whole world of Science.

At the end of May 1930, the director of the Lowell Observatory in Flagstaff Arizona, Vesto Slipher, announced that the name of the ninth planet would be Pluto. Venetia initially received little attention for being the one who thought up the name, but her grandfather did give her £5, which she said was a type of thing he did often for her: “As a grandfather, he liked to have an excuse for generosity.” Her grandfather also donated a “scrap of paper” and sent the letter noted above to her teacher, Miss Claxton, “… in grateful recognition of your share in Venetia’s triumphant naming of the new planet.” The money he sent with the letter was used to purchase a gramophone for use in teaching Music Appreciation; the gramophone was named “Pluto.”

In naming the planet, Venetia also named one very famous cartoon character: Mickey's dog. Some suggested that she named the planet after the dog, a notion that vexed Venetia. While the dog did appear in 1930, the same year Venetia suggested the name Pluto, his original name was “Rover.” He didn’t get the name “Pluto” until Moose Hunt, in April of 1931, about a year after the planet was named. “It has now been satisfactorily proven that the dog was named after the planet, rather than the other way around,” she told the BBC in 2006. “So, one is vindicated.”

Venetia died in 2009 at the age of 90, three years after Pluto was demoted to a dwarf planet.