Neptune

Planet Neptune

Neptune is the eighth known planet from the Sun. It carries the Roman name of Poseidon, the Greek god of the sea. Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Its blue colour is largely the result of absorption of red light by methane in the atmosphere.

The Planet

Neptune was found in 1846. The astronomers Urbain Le Verrier in France and John Couch Adams in England each calculated from irregularities in the orbit of Uranus where an unseen planet must lie, and Johann Galle in Berlin found it close to the place Le Verrier had predicted. Neptune has sixteen known moons. The largest, Triton, orbits in the direction opposite to the planet’s own rotation. The planet and its moon were named after the sea god and his son.

Poseidon, the God Behind the Name

The Greeks called the sea god Poseidon; Neptune is his Roman name, and Virgil uses it for the god in the Aeneid. According to Hesiod, Poseidon was one of the children of Cronus and Rhea (Theogony 453–458). In Homer, Poseidon himself says that he and his brothers Zeus and Hades divided the world between them by lot: he received the grey sea to live in, Hades the misty darkness below and Zeus the broad sky, while earth and Olympus remained common to all (Iliad 15.187–193). Apollodorus gives the same division and says that the Cyclopes gave Poseidon his trident (Apollodorus, Library 1.2.1).

Poseidon’s wife was Amphitrite, and Hesiod names their son as Triton, a great god who lives with his parents in a golden house in the depths of the sea (Hesiod, Theogony 930–933). The moon Triton is named for him.

Myths of Poseidon

Poseidon is the main divine enemy of Odysseus in the Odyssey. He is angry because Odysseus blinded the Cyclops Polyphemus, whose mother, the nymph Thoosa, daughter of Phorcys, had lain with Poseidon in a hollow cave (Homer, Odyssey 1.68–75).

In the Iliad, Poseidon tells Apollo how the two of them served King Laomedon of Troy for a year for wages, and how he built the wall around the city while Apollo herded the king’s cattle (Iliad 21.441–457). Apollodorus gives a related story, in which Poseidon sent a sea monster against Troy after Laomedon had wronged the gods (Apollodorus, Library 2.5.9).

In Virgil’s Aeneid, Neptune notices that a storm sent by Juno has stirred up the sea, rises from the waves, rebukes the winds and calms the water, and the Trojans reach the coast of Libya (Aeneid 1.124–158).