Astronomical symbols are abstract pictorial symbols used to represent astronomical objects, theoretical constructs and observational events in European astronomy. The earliest forms of these symbols appear in Greek papyrus texts of late antiquity. The Byzantine codices in which many Greek papyrus texts were preserved continued and extended the inventory of astronomical symbols. New symbols have been invented to represent many planets and minor planets discovered in the 18th to the 21st centuries.
These symbols were once commonly used by professional astronomers, amateur astronomers, alchemists, and astrologers. While they are still commonly used in almanacs and astrological publications, their occurrence in published research and texts on astronomy is relatively infrequent, with some exceptions such as the Sun and Earth symbols appearing in astronomical constants, and certain zodiacal signs used to represent the solstices and equinoxes.
Unicode has encoded many of these symbols, mainly in the Miscellaneous Symbols, Miscellaneous Symbols and Arrows, Miscellaneous Symbols and Pictographs, Alchemical Symbols, and Miscellaneous Symbols Supplement blocks.
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Sun and Moon The use of astronomical symbols for the Sun and Moon dates to antiquity. The forms of the symbols that appear in the original papyrus texts of Greek horoscopes are a circle with one ray () for the Sun and a crescent for the Moon. The modern Sun symbol, a circle with a dot (☉), first appeared in Europe in the Renaissance.
In modern academic writing, the Sun symbol is used for astronomical constants relating to the Sun. Teff☉ represents the solar effective temperature, and the luminosity, mass, and radius of stars are often represented using the corresponding solar constants (, , and , respectively) as units of measurement.
+ Sun Referent Symbol Unicodecode point Browserdisplay Represents Sun U+2609 Standard astronomical symbol U+1F71A the Sun with one ray U+1F31E the face of the Sun or "Sun in splendor"
+ Moon and lunar phasesThe American Practical Navigator, chapter 13, 'Navigational Astronomy' Referent Symbol Unicodecode point Browsertext displayText display is forced by appending U+FE0E to the character. Emojis are forced by appending U+FE0F. RepresentsMoon U+263D an increscent (waxing) moon(as viewed from the northern hemisphere) U+263E a decrescent (waning) moon(as viewed from the northern hemisphere) new moon U+1F311 fully dark U+1F31A waxing crescent U+1F312 encrescent moon (northern hemisphere) first-quarter (waxing) moon U+1F313 one week into the month, half the visible face illuminated Jim Maynard, Celestial Calendars or U+1F31B waxing gibbous U+1F314 (northern hemisphere) full moon U+1F315 fully illuminated U+1F31D waning gibbous U+1F316 (northern hemisphere)last-quarter (waning) moon U+1F317 final week of the month, the other half of the visible face illuminated or U+1F31C waning crescent U+1F318 decrescent moon (northern hemisphere)
Planets
Symbols for the classical planets appear in many medieval Byzantine codices in which many ancient horoscopes were preserved. The written symbols for Mercury, Venus, Jupiter, and Saturn 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 A.S.D. 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, 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.
A diagram in Byzantine astronomer Johannes Kamateros's 12th century Compendium of Astrology shows the Sun represented by the circle with a ray, Jupiter by the letter Zeta (the initial of Zeus, Jupiter's counterpart in Greek mythology), Mars by a shield crossed by a spear, and the remaining classical planets by symbols resembling the modern ones, without the cross-mark at the bottom of the modern versions of the symbols for Mercury and Venus. These cross-marks first appear 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."
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 the planetary elements iron, ♂, and gold, ☉. Another symbol, , was suggested by Joseph Jérôme Lefrançois de Lalande in 1784. In a letter to William 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"). Today, Köhler's symbol is more common among astronomers, and Lalande's among astrologers, although it is not uncommon to see each symbol in the other context.
Several symbols were proposed for Neptune to accompany the suggested names for the planet. Claiming the right to name his discovery, Urbain Le Verrier originally proposed the name Neptune and the symbol of a trident, while falsely stating that this had been officially approved by the French Bureau des Longitudes. In October, he sought to name the planet Leverrier, after himself, and he had loyal support in this from the observatory director, François Arago, who in turn proposed a new symbol for the planet (). However, this suggestion met with stiff resistance outside France. French almanacs quickly reintroduced the name Herschel for Uranus, after that planet's discoverer Sir William Herschel, and Leverrier for the new planet. Professor James Pillans of the University of Edinburgh defended the name Janus for the new planet, and proposed a key for its symbol. Meanwhile, German-Russian astronomer Friedrich Georg Wilhelm von Struve presented the name Neptune on December 29, 1846, to the Saint Petersburg Academy of Sciences. In August 1847, the Bureau des Longitudes announced its decision to follow prevailing astronomical practice and adopt the choice of Neptune, with Arago refraining from participating in this decision.
The International Astronomical Union discourages the use of these symbols in journal articles, though they do occur.E.g. p. 10, fig. 3 in Chen & Kipping (2017) Probabilistic Forecasting of the Masses and Radii of Other Worlds , The Astrophysical Journal, 834: 1. In certain cases where planetary symbols might be used, such as in the headings of tables, the IAU Style Manual permits certain one- and (to disambiguate Mercury and Mars) two-letter abbreviations for the names of the planets.
{| class="wikitable skin-invert-image" style="text-align: center;" |+ Planets |- ! scope="col" | Planet !! scope="col" | IAUabbreviation !! scope="col" | Symbol !! scope="col" | Unicodecode point !! scope="col" | Browserdisplay !! scope="col" | Represents |- | scope="row" | Mercury | H, Me | align=center | | U+263F | | style="text-align: left;" | Mercury's caduceus, with a cross |- | scope="row" | Venus | V | align=center | | U+2640 | | style="text-align: left;" | Perhaps Venus's necklace or a (copper) hand mirror, with a cross |- | scope="row" rowspan="2" | Earth | rowspan="2" | E | align=center | | U+1F728 | | style="text-align: left;" | the four quadrants of the world, divided by the four rivers descending from EdenUnicode characters with a similar shape: :U+2295 ⊕ CIRCLED PLUS; :U+2A01 ⨁ N-ARY CIRCLED PLUS OPERATOR; U+1F310 🌐︎ GLOBE WITH MERIDIANS |- | align=center | | U+2641 | | style="text-align: left;" | a globus cruciger |- | scope="row" | Mars | M, Ma | align=center | | U+2642 | | style="text-align: left;" | Mars's shield and spear |- | scope="row" | Jupiter | J | align=center | | U+2643 | | style="text-align: left;" | the letter Zeta with an abbreviation stroke (for Zeus, the Greek equivalent to the Roman god Jupiter) |- | scope="row" | Saturn | S | align=center | | U+2644 | | style="text-align: left;" | the letters kappa-rho with an abbreviation stroke (for Kronos, the Greek equivalent to the Roman god Saturn), with a cross |- | scope="row" rowspan=2| Uranus |rowspan=2| U |align=center| | U+26E2 | | style="text-align: left;" | symbol of the recently described element platinum, which was invented to provide a symbol for Uranus |- | align=center | | U+2645 | | style="text-align: left;" | a globe surmounted by the letter H (for Herschel, who discovered Uranus)(more common in older or British literature) |- | scope="row" rowspan=2|Neptune | rowspan=2|N | align=center | | U+2646 | | style="text-align: left;" | Neptune's trident |- | align=center | | U+2BC9 | | style="text-align: left;" | a globe surmounted by the letters "L" and "V", (for Le Verrier, who discovered Neptune)(more common in older, especially French, literature)
Asteroids
Following the discovery of Ceres in 1801 by the astronomer and Catholic priest Giuseppe Piazzi, a group of astronomers ratified the name, which Piazzi had proposed. At that time, the sickle was chosen as a symbol of the planet.
The symbol for 2 Pallas, the spear of Pallas Athena, was invented by Baron Franz Xaver von Zach, who organized a group of twenty-four astronomers to search for a planet between the orbits of Mars and Jupiter. The symbol was introduced by von Zach in 1802. In a letter to von Zach, discoverer Heinrich Wilhelm Matthäus Olbers (who had discovered and named Pallas) expressed his approval of the proposed symbol, but wished that the handle of the sickle of Ceres had been adorned with a pommel instead of a crossbar, to better differentiate it from the sign of Venus.
German astronomer Karl Ludwig Harding created the symbol for 3 Juno. Harding, who discovered this asteroid in 1804, proposed the name Juno and the use of a scepter topped with a star as its astronomical symbol.
The symbol for 4 Vesta was invented by German mathematician Carl Friedrich Gauss. Olbers, having previously discovered and named 2 Pallas, gave Gauss the honor of naming his newest discovery. Gauss decided to name the new asteroid for the goddess Vesta, and also designed the symbol (): the altar of the goddess, with the sacred fire burning on it. Other contemporaneous writers use a more elaborate symbol () instead.
Karl Ludwig Hencke, a German amateur astronomer, discovered the next two asteroids, 5 Astraea (in 1845) and 6 Hebe (in 1847). Hencke requested that the symbol for 5 Astraea be an upside-down anchor; however, a weighing scale was sometimes used instead. Gauss named 6 Hebe at Hencke's request, and chose a wineglass as the symbol.
As more new asteroids were discovered, astronomers continued to assign symbols to them. Thus, 7 Iris (discovered 1847) had for its symbol a rainbow with a star; 8 Flora (discovered 1847), a flower; 9 Metis (discovered 1848), an eye with a star; 10 Hygiea (discovered 1849), an upright snake with a star on its head; 11 Parthenope (discovered 1850), a standing fish with a star; 12 Victoria (discovered 1850), a star topped with a branch of laurel; 13 Egeria (discovered 1850), a buckler; 14 Irene (discovered 1851), a dove carrying an olive branch with a star on its head; 15 Eunomia (discovered 1851), a heart topped with a star; 16 Psyche (discovered 1852), a butterfly wing with a star; 17 Thetis (discovered 1852), a dolphin with a star; 18 Melpomene (discovered 1852), a dagger over a star; and 19 Fortuna (discovered 1852), a star over Fortuna's wheel.