section_path: Mythology and naming/Symbols
section_name: Symbols
paragraph_text: Symbols
  
  The written symbols for Mercury, Venus, Jupiter, Saturn, and possibly Mars have been traced to forms found in late Greek papyrus texts. The symbols for Jupiter and Saturn are identified as monograms of the corresponding Greek names, and the symbol for Mercury is a stylized caduceus.
  
  According to Annie Scott Dill Maunder, antecedents of the planetary symbols were used in art to represent the gods associated with the classical planets. Bianchini's planisphere, discovered by Francesco Bianchini in the 18th century but produced in the 2nd century, shows Greek personifications of planetary gods charged with early versions of the planetary symbols. Mercury has a caduceus; Venus has, attached to her necklace, a cord connected to another necklace; Mars, a spear; Jupiter, a staff; Saturn, a scythe; the Sun, a circlet with rays radiating from it; and the Moon, a headdress with a crescent attached. The modern shapes with the cross-marks first appeared around the 16th century. According to Maunder, the addition of crosses appears to be "an attempt to give a savour of Christianity to the symbols of the old pagan gods." Earth itself was not considered a classical planet; its symbol descends from a pre-heliocentric symbol for the four corners of the world.
  
  When further planets were discovered orbiting the Sun, symbols were invented for them. The most common astronomical symbol for Uranus, ⛢, was invented by Johann Gottfried Köhler, and was intended to represent the newly discovered metal platinum. An alternative symbol, ♅, was invented by Jérôme Lalande, and represents a globe with a H on top, for Uranus's discoverer Herschel. Today, ⛢ is mostly used by astronomers and ♅ by astrologers, though it is possible to find each symbol in the other context. The first few asteroids were considered to be planets when they were discovered, and were likewise given abstract symbols, e.g. Ceres' sickle (⚳), Pallas' spear (⚴), Juno's sceptre (⚵), and Vesta's hearth (⚶). However, as their number rose further and further, this practice stopped in favour of numbering them instead. (Massalia, the first asteroid not named from mythology, is also the first asteroid that was not assigned a symbol by its discoverer.) The symbols for the first four asteroids, Ceres through Vesta, remained in use for longer than the others, and even in the modern day NASA has used the Ceres symbol—Ceres being the only asteroid that is also a dwarf planet. Neptune's symbol (♆) represents the god's trident. The astronomical symbol for Pluto is a P-L monogram (♇), though it has become less common since the IAU definition reclassified Pluto. Since Pluto's reclassification, NASA has used the traditional astrological symbol of Pluto (⯓), a planetary orb over Pluto's bident.
  
  The IAU discourages the use of planetary symbols in modern journal articles in favour of one-letter or (to disambiguate Mercury and Mars) two-letter abbreviations for the major planets. The symbols for the Sun and Earth are nonetheless common, as solar mass, Earth mass, and similar units are common in astronomy. Other planetary symbols today are mostly encountered in astrology. Astrologers have resurrected the old astronomical symbols for the first few asteroids and continue to invent symbols for other objects. This includes relatively standard astrological symbols for the dwarf planets discovered in the 21st century, which were not given symbols by astronomers because planetary symbols had mostly fallen out of use in astronomy by the time they were discovered. Many astrological symbols are included in Unicode, and a few of these new inventions (the symbols of Haumea, Makemake, and Eris) have since been used by NASA in astronomy. The Eris symbol is a traditional one from Discordianism, a religion worshipping the goddess Eris. The other dwarf-planet symbols are mostly initialisms (except Haumea) in the native scripts of the cultures they come from; they also represent something associated with the corresponding deity or culture, e.g. Makemake's face or Gonggong's snake-tail.