Period 6 element
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78.
Astronomical symbols
The symbols for Uranus were created shortly after its discovery. One symbol, , invented by J. G. Köhler and refined by Bode, was intended to represent the newly discovered metal platinum; since platinum, commonly called white gold, was found by chemists mixed with iron, the symbol for platinum combines the alchemical symbols for iron, ♂, and gold, ☉. This symbol also combines the symbols of Mars (♂) and the Sun (☉) because in Greek mythology Uranus represented heaven, and represents the combined power of Mars's spear and the Sun. 
Another symbol, , was suggested by Lalande in 1784. In a letter to Herschel, Lalande described it as "un globe surmonté par la première lettre de votre nom" ("a globe surmounted by the first letter of your name").