Sky & sea · the planets

Planets and their names

“Planet” is Greek for wanderer: five bright points that move against the fixed stars. The Romans gave them the names of their gods, and those names, with the old symbols, came down through astronomy and alchemy to us. Two more planets, found by telescope, were named to fit the pattern.

Orrery

Date

true distances

Each dashed line runs from the Earth to a planet: the direction you would look. Press Play to watch a few years go by.

Planet	Angle from the Sun	Where to look	In front of	From Earth

Seen from above the north pole of the ecliptic; the arrow marks the direction of the March equinox. Distances are drawn on a square-root scale unless you tick true distances. Positions: Approximate Positions of the Planets: Keplerian elements and rates, Table 1 (1800–2050), good to about an arcminute between 1800 and 2050. The build checks this code against a published worked example for Venus (1992 December 20) and against an independent formula for the Sun.

Names, gods and symbols

	Name	Roman figure	Why the name	IAU abbr.	Moons
☉︎	Sun U+2609	Sol Greek: Helios	A circle with a dot at its centre. Astronomers still use it in M☉, the mass of the Sun, as a unit.	—	—
☾︎	Moon U+263E	Luna Greek: Selene	A crescent. Our moon has no other English name; the moons of other planets have their own names.	—	—
☿︎	Mercury U+263F	Mercury, messenger of the gods Greek: Hermes	The fastest planet, round the Sun in 88 days, so it bears the messenger’s name; the symbol is his staff.	Me	0
♀︎	Venus U+2640	Venus, goddess of love and beauty Greek: Aphrodite	The brightest planet. Its symbol, often read as a hand mirror, became the biologists’ sign for female.	V	0
♁︎	Earth U+2641	Terra (Tellus) Greek: Gaia	The only planet whose English name comes from neither myth: Old English eorþe, “ground”. In formulas the circled cross ⊕ is used, as in M⊕.	E	1
♂︎	Mars U+2642	Mars, god of war Greek: Ares	Its blood-red colour suited the god of war. Its symbol, a shield and spear, became the sign for male.	Ma	2
♃︎	Jupiter U+2643	Jupiter, king of the gods Greek: Zeus	The largest planet takes the name of the chief god.	J	95
♄︎	Saturn U+2644	Saturn, god of sowing, father of Jupiter Greek: Kronos	The slowest planet known in antiquity, about 29½ years round the Sun; the symbol is his sickle.	S	274
♅︎	Uranus U+2645	none: the name is Greek Greek: Ouranos, the sky, father of Kronos	Found by William Herschel in 1781, who called it Georgium Sidus after King George III. Johann Bode proposed Uranus, completing the line sky → Saturn → Jupiter. It is the only planet named after a Greek god.	U	28
♆︎	Neptune U+2646	Neptune, god of the sea Greek: Poseidon	Found by Johann Galle in Berlin on 23 September 1846, close to the position Urbain Le Verrier had calculated from the pull it exerted on Uranus. The symbol is the sea god’s trident.	N	16
♇︎	Pluto U+2647	Pluto, god of the underworld Greek: Hades	Found by Clyde Tombaugh in 1930; the name was suggested by Venetia Burney, aged 11. The IAU made it a dwarf planet in 2006.	P	—

Moon counts: Planetary Fact Sheet, metric (updated 18 March 2025) (March 2025); they grow as new small moons are confirmed. Abbreviations: IAU Style Manual 1989, 5.25. Symbols: Unicode.

Configurations

Old almanacs printed these as symbols beside the planets. The table above the orrery says which one each planet is in today.

☌	Conjunction	Two bodies at the same ecliptic longitude as seen from Earth. A planet in conjunction with the Sun is lost in its glare.
☍	Opposition	An outer planet opposite the Sun in the sky: closest to Earth, brightest, and up all night.
□	Quadrature	An outer planet 90° from the Sun, due south at sunrise or sunset.
	Greatest elongation	An inner planet (Mercury or Venus) at its greatest angle from the Sun: about 18–28° for Mercury, 45–47° for Venus.

Then and now

The IAU’s style manual (1989) says the special symbols for planets and for phenomena such as conjunctions “should not be used” in astronomical writing: write the word, and in table headings use letters such as Ma for Mars. Only ☉ and ⊕ survive, in M☉ and M⊕. Pluto was counted as the ninth planet from 1930 until 2006, when the IAU defined a planet as a body that has cleared its orbit and made Pluto a dwarf planet (IAU 2006, Res. B5/B6).