plutonium, Pluto

Plutonium, element 94, was first produced in 1940 at the University of California, Berkeley by chemist Glenn Seaborg and physicist Edwin McMillan. The element is named for the planet Pluto (now officially defined as a dwarf planet), following the pattern set by uranium and neptunium. The first recorded use of the term is by Seaborg and Arthur Wahl in a 1942 government report:

Since such formulae are confusing when the symbols “93” and “94” are used, we have decided to use symbols of the conventional chemical type to designate these elements. Following McMillan, who has suggested the name neptunium [...] for element 93, we are using plutonium [...] for element 94. The corresponding chemical symbols would be Np and Pu.1

Pluto was discovered on 13 March 1930 by Clyde Tombaugh of the Lowell Observatory in Flagstaff, Arizona. The name Pluto, after the Roman god of the underworld, was suggested by British schoolgirl Venetia Burney. Burney’s grandfather, a former librarian at the Bodleian Library in Oxford, passed his granddaughter’s suggestion on to an astronomer colleague, who in turn cabled it to the Lowell Observatory. The staff at the Lowell voted to adopt Pluto as the name on 24 March.2 The name was also considered a tribute to Percival Lowell, whose initials are the first two letters of the name. The 23 March 1930 New York Times quotes Charles Freeman, superintendent of the US Naval Observatory:

The new body is doubtless “Lowell’s planet,” as Uranus was “Herschel’s planet,” but it will be quite impossible to have the world at large accept Lowell as a lasting name any more than to attach the name Leverrier to Neptune was successful.

That same article is also the first published use of Pluto as a (then potential) name for the planet, but suggests that it would not be officially adopted:

Pluto is the prototype of Satan in many minds, and drops out for that reason perhaps.3

Later, the Times reported the official naming:

[Roger Lowell] Putnam added that Pluto lent itself easily to the monogram “P.L.,” the initials of Percival Lowell, and “would be a fitting memorial to him.”4

1Oxford English Dictionary, plutonium, 3rd Edition, December 2008, Oxford University Press, accessed 20 November 2009,

2”Venetia Phair Dies at 90; as a Girl, She Named Pluto,” The New York Times, 10 May 2009,

3”Naval Observatory Films New Planet,” The New York Times, 23 March 1930, p. 27.

4”Pluto Picked as the Name for New Planet X,” The New York Times, 26 May 1930, p. 1.

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