Real astronomy and history of the stars, with sources. Star stories from named traditions. Star symbolism · symbolic, not predictive.

Star symbolism · Symbolic interpretation

What are fixed stars in astrology?

In astrology the fixed stars are the stars proper, as opposed to the planets, which wander. Ptolemy gave them a chapter in the second century; here is what he wrote, and why the stars were never quite fixed.

Fixed and wandering

Planets were the ‘wandering stars’; everything else was fixed.

The word planet comes from the Greek for “wandering stars” (opens in a new tab): the planets were named for their motion against the stars that seemed to stay put. Those were the fixed stars, and astrology kept the name.

Medieval cosmology placed them all on one sphere: the Met describes al-Sufi's book on the 48 constellations of the fixed stars (opens in a new tab), which were thought to occupy the eighth of nine spheres around the Earth.

Sources for this section Online Etymology Dictionary, planet (opens in a new tab); The Metropolitan Museum of Art, Kitab suwar al-kawakib al-thabita (Book of the Images of the Fixed Stars) of al-Sufi (13.160.10) (opens in a new tab)

Ptolemy's chapter

Ptolemy described each group of stars by comparing it to one or two planets.

In the Tetrabiblos, book I, chapter 9, “Of the Power of the Fixed Stars” (opens in a new tab), Ptolemy works through the stars group by group, zodiac first, then north and south of it, and gives each a nature by comparing it with the planets. His translator, F. E. Robbins, identifies the stars where the text names them only by place.

The table below reports his assignments (opens in a new tab) for stars and groups that have guides on this site. It paraphrases one ancient author; it is not current practice everywhere, not a measurement, and not a key to anyone's character.

Ptolemy, Tetrabiblos I.9 (tr. Robbins): what he compared each star or group with
Star or groupPtolemy's comparisonNote
The Pleiades, in TaurusThe Moon and JupiterAn open cluster; Ptolemy treats it as part of the bull.
The Torch, among the HyadesMarsRobbins's note identifies the Torch as Aldebaran, “bright and somewhat reddish”.
Regulus, the lion's heartMars and Jupiter—
Spica, in VirgoVenus and, less, MarsRobbins notes Spica marked the ear of wheat in the maiden's hand.
Antares, in the scorpionMars and, in some degree, Jupiter“Tawny and rather bright.”
Arcturus, in BoötesJupiter and Mars“The bright, tawny star.”
The stars of LyraVenus and Mercury—
The stars of CygnusVenus and MercuryPtolemy: “and likewise those in Cygnus”.
Orion's shouldersMars and MercuryOrion's other bright stars: Jupiter and Saturn.
The bright stars of Ursa MajorMarsThose of Ursa Minor: Saturn and, less, Venus.
Sirius, the bright star in the Dog's mouthJupiter and, less, Mars—
The bright stars of AurigaMars and MercuryCapella is Auriga's brightest.

Sources for this section Ptolemy, Tetrabiblos I.9, Of the Power of the Fixed Stars, tr. F. E. Robbins (Loeb, 1940), LacusCurtius (opens in a new tab)

When the old figures do not match today's

Ptolemy's groups follow the Greek figures, which do not always fit the IAU's modern boundaries.

Some of Ptolemy's groups have no modern equivalent. He describes the stars in the Claws of the Scorpion (opens in a new tab), which the Romans had already made into Libra (opens in a new tab), and he treats the Pleiades as part of the bull rather than as a separate object.

The IAU's constellations (opens in a new tab) are areas with boundaries drawn in 1928, not figures, so a star Ptolemy placed in one figure can fall in a different modern constellation. The Southern Cross is the clearest case: it has no entry of its own in his chapter at all.

Sources for this section Ptolemy, Tetrabiblos I.9, Of the Power of the Fixed Stars, tr. F. E. Robbins (Loeb, 1940), LacusCurtius (opens in a new tab); Ian Ridpath, Star Tales: Libra (opens in a new tab); International Astronomical Union, The Constellations (opens in a new tab)

The fixed stars move

Stars drift on their own, and the zodiac slides against them: a fixed-star table needs a date.

The stars move through space. By this site's calculation from the Bright Star Catalogue, Arcturus has moved about 1.2 degrees since Ptolemy wrote, and Alpha Centauri more still; ESA explains (opens in a new tab) why nearby stars drift fastest.

And Earth's axis wobbles, a cycle of about 25,771 years (opens in a new tab), which slides every star's position in the tropical zodiac forward by about a degree every 72 years: by that arithmetic, some 26 degrees since the second century.

Sources for this section ESA, How does Gaia study the Milky Way? (opens in a new tab); NASA Science, Milankovitch (Orbital) Cycles and Their Role in Earth's Climate (2020) (opens in a new tab)

Reflect

A Cool Star Facts reflection prompt

  1. Pick a bright star you can actually find: Sirius, Vega, Antares.
  2. Look at it for a minute. Write down what you would compare it to, a colour, a sound, a person, and why.
  3. Then read what Ptolemy compared it to. Did you notice the same things he did, or different ones?

This prompt is this site's own. It is an exercise in looking, not a technique, and it predicts nothing.

Sources

Practitioner sources tell you what those practitioners say. They are not evidence that the stars do it.

Stars in astrology & myth →

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