‘What about the moon Tracey?’ asked my husband facetiously when an astronomer on the wireless, talking of Pluto’s moon Charon, pronounced it ‘Sharon’. As usual, things turn out not to be so simple as my husband’s understanding of them.

Everyone knows that Pluto was named in 1930 by an 11-year-old girl, Venetia Burney. Her mother, the sister of the quirky belletrist Geoffrey Madan, was the daughter of Falconer Madan, Bodley’s Librarian. Madan mentioned the discovery of the new planet to his granddaughter, who came up with the name Pluto, god of the underworld, which Falconer Madan mentioned to the Savilian Professor of Astronomy at Oxford, who cabled the Lowell Observatory in Arizona. Clyde Tombaugh liked the name, partly for the weak reason that it incorporated the initial and start of the name of his patron Percival Lowell.

In 1978 a blob on the tiny image of Pluto was discerned as a moon by James Christy, of the US Naval Observatory. His wife’s name was Charlene, and she was known as Char, pronounced Shar. He wanted the moon’s name to commemorate her, so he continued to pronounce the name of the ferryman of the Styx as Sharon instead of the ordinary way with a hard ch. So, present-day astronomers persist with this, some knowingly.

Some Americans pronounced Sharon to rhyme with Charon, as do some British people when they are talking about Sharon’s rose; others make the first syllable rhyme with far, and yet others put the stress on the second syllable of Sharon, like the most common way of pronouncing the name of the late Ariel Sharon.

We got off lightly. Christy contemplated calling the moon Oz, it seems. As for Pluto, it too was lucky to receive a classical if hellish name. Clyde Tombaugh named other notable asteroids Kathleen, Patsy and Brendalee. Another he called McKellar, not after the Scottish tenor Kenneth McKellar (who had seemed to reciprocate with his hit ‘The Song of the Clyde’), but after the Canadian astronomer Andrew McKellar, who put the temperature of interstellar space at about 2 degrees Kelvin.