Phosphorus is the Morning Star, the planet Venus in its morning appearance.

Phaosphoros and Phaesphoros are forms of the same name in some Greek dialects. This celestial object was named when stars and planets were not always distinguished with modern precision.

Another Greek name for the Morning Star is Heosphoros, meaning “Dawn-Bringer“. The form Eosphorus is sometimes met in English, as if from Ēōsphoros, which is not actually found in Greek literature but would be the form that Heosphoros would have in some dialects.

As an adjective, the Greek word Phosphorus is applied in the sense of “light-bringing” to, for instance, the dawn, the god Dionysos, pine torches, the day; and in the sense of “torch-bearing” as an epithet of several god and goddesses, especially Hecate but also of Artemis/Diana and Hephaestus.

The Latin word Lucifer, corresponding to Greek Phosphorus, was used as a name for the morning star and thus appeared in the Vulgate translation of the Hebrew word helel, meaning Venus as the brilliant, bright or shining one, in Isaiah 14, where the Septuagint Greek version uses, not Phosphorus, but Heosphoros.

As a translation of the same Hebrew word the King James Version gave “Lucifer“, a name often misunderstood as a reference to Satan. Modern translations of the same passage render the Hebrew word instead of as “morning star“, “daystar“, “shining one” or “shining star“.

In Revelation 22 (Revelation 22:16), Jesus is referred to as the morning star, but not as lucifer in Latin, nor as Phosphorus in the original Greek text, which instead has o astēr o lampros o prōinos, literally: the star, the shining one, the dawn.

In the Vulgate Latin text of 2, Peter 1 ( 2 Peter 1:19) the word “Lucifer” is used of the morning star in the phrase “until the day dawns and the morning star rises in your hearts“, the corresponding Greek word being Phosphorus.


The morning star is an appearance of the planet Venus, an inferior planet, meaning that its orbit lies between that of the Earth and the Sun.

Depending on the orbital locations of both Venus and Earth, it can be seen in the eastern morning sky for an hour or so before the Sun rises and dims it, or (as the evening star) in the western evening sky for an hour or so after the Sun sets, when Venus itself then sets.

Venus is the brightest object in the sky after the Sun and the Moon, outshining the planets Jupiter and Saturn but, while these rise high in the sky, Venus never does.

This may lie behind myths about deities associated with the morning star proudly striving for the highest place among the gods and being cast down.


In Greek mythology, Hesiod calls Phosphorus a son of Astraeus and Eos, but other say of Cephalus and Eos, or of Atlas.

The Latin poet Ovid, speaking of Phosphorus and Hesperus (the Evening Star, the evening appearance of the planet Venus) as identical, makes him the father of Daedalion.

Ovid also makes him the father of Ceyx, while the Latin grammarian Servius makes him the father of the Hesperides or of Hesperis.

While at an early stage the Morning Star (called Phosphorus and other names) and the Evening Star (referred to by names such as Hesperus) were thought of as two celestial objects, the Greeks accepted that the two were the same, but they seem to have continued to treat the two mythological entities as distinct.

Halbertal and Margalit interpret this as indicating that they did not identify the star with the god or gods of mythology “embodied” in the star.

Hesperus is Phosphorus

In the philosophy of language, “Hesperus is Phosphorus” is a famous sentence in relation to the semantics of proper names.

Gottlob Frege used the terms “the evening star” (Der Abendstern) and “the morning star” (der Morgenstern) to illustrate his distinction between sense and reference, and subsequent philosophers changed the example to “Hesperus is Phosphorus” so that it utilized proper names.

Saul Kripke used the sentence to posit that the knowledge of something necessary — in this case the identity of Hesperus and Phosphorus — could be discoverable rather than known a priori.


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