Celeris, the brother of Pegasus that never existed
If you read about constellations, you may come across the name "Celeris" for Equuleus, the Little Horse next to the stars of Pegasus. You might even hear that Celeris is the brother of Pegasus in mythology, gifted to Castor by the god Mercury... But here's the twist : it's all a Victorian invention. One that has been repeated so often that most people take it as fact without challenging it. So, what do the ancient sources actually say ? I've gathered all the original texts, even the more obscure ones. Join me on a deep dive no one has really taken before and discover the truth behind this mythical horse !
Celeris or Cyllarus ?
The name Celeris, often linked today with the constellation Equuleus, does not come from any ancient Greek or Roman myth. In fact, it appears to be a mistake from 19th century English writers. Everything we hear about the supposed horse Celeris can be traced back to Victorian-era writers who repeated each other's mistakes, never being challenged or corrected.
The first mention of Celeris in this context is from 1824 :
"This constellation represents, according to the Poets, the horse named Celeris, given by Mercury to Castor, who was celebrated for his skill in the management of this noble animal" — Jacob Green, Astronomical Recreations (1824)
This is actually a misspelling of the name "Cyllarus". Earlier sources about Equuleus being a horse given to Castor by Mercury use the correct name :
"CHEVAL (Astron.) equuleus, equus minor, etc. Constellation qu'on appelle communément petit cheval ; pour la distinguer de Pégase qui est le grand cheval ; on n'en voit sur les cartes que la moitié, comme si le reste du corps étoit caché par les nuages. Suivant la mythologie, ce cheval est celui que Mercure avoit donné à Castor, & qui se nommoit Cyllarus, (Virg. Georg. III)"
(Constellation commonly called the little horse ; to distinguish it from Pegasus which is the big horse ; only half of it is shown on maps, as if the rest of the body were hidden by the clouds. According to mythology, this horse is the one Mercury gave to Castor, and which was named Cyllarus, (Virg. Georg. III)) — Diderot, Encyclopédie (1776)
This quote vastly predates the earliest mention of "Celeris", and appears in other late 18th century French texts. Some sources even go further and specify :
"CYLLARUS, fils de Podarga, beau cheval donné par Mercure à Castor et à Pollux ; selon d'autres, Neptune le donna à Junon et celle-ci aux Dioscures"
(Cyllarus, son of Podarge, beautiful horse given by Mercury to Castor and Pollux ; according to others, Neptune gave him to Juno and she, to the Dioscuri) — Pierre Chompre, Dictionnaire portatif de la Fable (1801)
Similarly, the names "Kyllaros" and "Cyllarus", not Celeris, are mentioned in older books in other languages, like the star atlases of the Austrian monk Corbinianus Thomas (Manuductio ad Astronomiam (1730) and Mercurii Philosophici Firmamentum Firmianum (1730)), or Christian Gottlieb Semler's Astrognosia Nova (1742).
Cyllarus is an attested character, a horse of the Dioscuri (i.e., the twins Castor and Pollux). Meanwhile, the name Celeris appears to be a 19th century mix-up : the word celeris is a real Latin word meaning "swift", which, admittedly, would be fitting for a horse name (except it would be spelled "Celer"). Interestingly, we also find some 19th century English texts mentioning a horse of the emperor Lucius Verus named Celer... Which is another misunderstanding, as that horse was actually named Volucer ("Flying", alluding to the horse's swiftness). Volucer was the emperor's favorite racehorse from the Greens, the chariot team he was a sports fan of.
So, "Celeris" isn't a genuine thing... But this is barely scratching the surface. There's a whole rabbit hole of mistakes and misconceptions about that horse, spanning centuries.
Horse of the Dioscuri, horse of Mercury ?
The versions that use "Cyllarus" make sense, since traditionally, the horses of the Dioscuri are called Xanthus (Ξανθος, Xanthos) and Cyllarus (Κύλλαρος, Kyllaros). These names appear in both ancient Greek and Roman texts. Depending on the version, Cyllarus can be the horse of Castor, of Pollux, or even be a horse that the brothers share alternately.
There's a small problem, though... The previous sources I quoted that mentioned Cyllarus as a gift from Mercury cannot be considered reliable. They contain another mix-up : Cyllarus was neither given by Mercury (Hermes) nor born from the Harpy Podarge in the original texts. That spot belongs to the horses Harpagus (Ἁρπαγος, Harpagos) and Phlogeus (Φλογευς, Phlogeus), both of whom were gifted by Hermes to the twins. This confusion stems from a misreading of a fragment from Stesichorus :
"Ἑρμείας μὲν ἔδωκεν Φλόγεόν τε καὶ Ἄρπαγον , ὠκέα τέκνα Ποδάργας , ̔́Ἥρα δὲ Ξάνθον καὶ Κύλλαρον"
(Hermes gave Phlogeus and Harpagus, swift children of Podarge, and Hera gave Xanthus and Cyllarus.) — Stesichorus, Fragment 178 (7th-6th century BC)
So, Celeris from Mercury ? Not a thing. Cyllarus from Juno ? Real horse from mythology.
The "Brother of Pegasus"
Now let's tackle the most ludicrous claim... The idea that Celeris was Pegasus' brother. The first known mention of this appears in an English book from 1828 :
"EQUULEUS (the LITTLE HORSE,) a constellation of the northern hemisphere, called also EQUI SECTIO, from its representation as a horse's head ; is is between Delphinus and Pegasus, whose brother he was.
Pennisque fugacem Pegason et fratrem matris de sanguinem naso — OVID." — Robert Goodacre, A Glossary: or, Explanation of the principal terms used in the sciences of astronomy and geography (1828)
The Latin verse from Ovid which Goodacre quotes (apparently assuming it to be about a second horse) is actually about the giant Chrysaor, who, like Pegasus, famously sprang from Medusa's dead body. Chrysaor and Pegasus are the only offspring of Medusa in classical mythology, and Chrysaor is the only other creature born that way : the verse could not refer to any other being. Furthermore, Chrysaor is usually depicted as humanoid, there is no tradition where he is a second horse.
(The birth of Chrysaor and Pegasus, springing from Medusa's neck.)
Alas, this mistake spread quickly. Just a few years later, the American astronomer Elijah Hinsdale Burritt combined it with the story of "Celeris" (which clearly came from Green's book, as the wording is almost identical) :
"This constellation is supposed to be the brother of Pegasus, named Celeris, given by Mercury to Castor, who was so celebrated for his skill in his management of horses" — Elijah Hinsdale Burritt, The Geography of the Heavens (1833)
This doubly erroneous version continued to circulate, being included in books such as Richard Hinckley Allen's Star Names :
"Some mythologists have said that the constellation represented Celeris, the brother of Pegasus, given by Mercury to Castor ; or Cyllarus, given to Pollux by Juno" — Richard Hinckley Allen, Star Names (1899)
The two horses described are actually redundant doublets of the same figure, the one and only Cyllarus, sometimes said to be gifted to Pollux, sometimes to Castor, depending on the version of the story. By this point, it was too late. From then on the fiction of "Celeris" was copied in dozens of books about astronomy, with seemingly no one bothering to check the sources for two centuries.
Yet another mix-up : the coal-black Cyllarus
(Amphora from Exekias, showing the Dioscuri with their parents.)
On this amphora (which is pretty famous by the way... Well, the other side is, at least), Pollux is playing with his dog, while Castor is holding his horse, whose name is clearly specified : it's Kyllaros. Here's, he's shown as black... But that's because this is black-figure pottery and everyone is depicted this way.
Still, the idea that Cyllarus was a black horse remains a misconception that refuses to die to this day... Again, traced back to 19th century English and American publications (note the misspellings of the name Cyllarus) :
"Gilaros — According to Virgil, (Georg. III, 90,) this was the celebrated horse of Pollux, but Seneca, Claudian, and Ovid, (Metam. XII 408,) give it to Castor. It was named for Cylla, in Troas, and was of a coal-black color with the exception of the legs and tail which were white. The two brother mounted it alternately on the return from the infernal region." — Historic Magazine and Notes and Queries (1882)
(And the mention of Volucer, with the wrong name of "Celer" :)
"Cykaros, their other horse, was coal-black, with white mane and tail ; [...] Celer, the horse of the emperor Vereus, meant, of course, swift" — Wallace's Monthly, volume 19 (1893)
The 19th century misinterpretation of Ovid strikes again ! Cyllarus was not a black horse with a white mane and tail. This comes from a verse in the Metamorphoses, which is actually describing a centaur named Cyllarus. The centaur is the one with a coal-black equine body, not the divine horse. (The horse was also not named after the centaur, in fact, it's probably the other way around.)
As a matter of fact, the Dioscuri notoriously ride white horses... One of their Greek epithets is even Leukopōloi (Λευκόπωλοι, "with white horses"). This is what Pindar calls them, "λευκοπώλων Τυνδαριδᾶν", Tyndarides with white horses. And he's far from the only author to do so :
"...duos in candidis equis Castorem atque Pollucem nemo dubitarit."
(...two, mounted on white horses, whom none doubted but they were Castor and Pollux.) — Florus, The Roman History (2nd century AD)
Ovid himself describes the brothers' horses as white in the Metamorphoses :
"At gemini, nondum caelestia sidera, fratres, Ambo conspicui nive candidoribus ambo Vectambur equis"
(But now the Twin brothers, not yet set in the starry heavens, Came riding up, both conspicuous against the rest, Both on horses whiter than snow) — Ovid, Metamorphoses, book VIII.372 (1st century AD)
We have not only textual, but visual proof of this, as ancient artwork of the Dioscuri in color clearly does not show black horses :
(Left : One of the Dioscuri with his horse, Roman fresco from Pompeii, House of the Dioscuri (1st century AD).
Right : Castor and his horse, detail from the mosaic of the Triumph of Bacchus in the Museum of Écija (2nd century AD).)
And even Cyllarus' sons are described as white ! In the Thebaid, Statius writes that Cyllarus had foals with Spartan mares while his master, unaware, left him home to sail with the Argonauts. According to him, the descendants of Cyllarus are the racehorses of Amphiaraeus. Here's how his horse team and chariot racing outfit are described :
"Ipse habitu niveus, nivei dant colla jugales, Concolor est albis et cassis et infula cristis" (He himself wears snow white, snowy are the coursers that give their necks to the yoke, His helm and fillet match his white plume) — Statius, Thebaid (1st century AD)
These horses are called Caerus (the name of the personnification of Opportunity in mythology), Aschetus (a name derived from the Greek ἄσχετος (aschetos, "ungovernable"), likely referencing the horse's unruly temper), and Cycnus, "swan", whose name alludes to his color : "Increpitans Caerumque levem Cygnumque nivalem" ("calling aloud on nimble Caerus and snow-white Cygnus"). Which is, again, white.
Cyllarus... the Crab ?
Let's also quickly address another inaccuracy from a previous quote, the idea that the name Cyllarus allegedly derives from "Cylla in Troas". First, the city is spelled Cilla (Κίλλα, Killa), and this etymology is speculative at best. There's no serious source to back it up.
So, what does "Cyllarus" mean, then ? Well... To be fair, the exact details are a bit unclear. While one popular claim, often repeated over the centuries, derives it from κέλλειν (kellein, to drive ashore), and extrapolates from it a meaning of "the swift" (which ironically circles back to the word celeris in a roundabout way), ancient Greek dictionaries don't really support that idea, and instead have other leads.
In ancient Greek, κύλλαρος (kyllaros, also written as σκύλλαρος, skyllaros) was the name of a type of crab or hermit crab. In fact, some crustaceans are still named after the word : the Scyllaridae, or slipper lobsters (among which one genus is called Scyllarus). So, in a literal sense, Cyllarus is named... Hermit Crab.
(A slipper lobster.)
That word may originate, or be otherwise related, to κυλλός (kyllos, "crooked, twisted"). The god Hephaestus is sometimes described as κυλλοποδίων (kyllopodion, "with crooked feet"). This makes a lot of sense for a hermit crab, given the spiral shape of their adbomen. But for a horse...?
Who knows, maybe "Hermit Crab" was considered a fine horse name back then...? Or maybe the idea of a "curved" horse could refer to a horse curving its neck, like what Xenophon called, in his treaty On Horsemanship, κῡφαγωγός (kyphagōgos, from κῡφός (kyphos), "bent, curved, hunchbacked") ? Interestingly, in Phaedra, Cyllarus is mentioned alongside the word flectere, "to bend" :
"Si dorso libeat cornipedis vehi, Frenis Castorea mobilior manu Spartanum poteris flectere Cyllaron." ("Shouldst thou be pleased to ride a horn-footed horse, With hand more agile on the rein than Castor’s Thou couldst guide the Spartan Cyllarus.") — Seneca, Phaedra, 810 (1st century AD)
Of course, this quote doesn't automatically mean that there's an intentional hidden double meaning in it regarding the etymology of Cyllarus, but it's still interesting to note.
Regardless, in a way, even if the name only meant "crab" and nothing more, the marine theme wouldn't be too out of place either, as the idea of Neptune giving the horses to Juno (who then gifted them to the twins) is actually backed by an ancient quote, according to a Virgilian scholiast :
"Equos autem a Neptuno Iunoni datos Alcman lyricus dicit Cyllarum et Xanthum"
(However, the lyric poet Alcman calls the horses given by Neptune to Juno, Cyllarus and Xanthus) — Scholia Bernensia (Georgica, III.89.)
But another noteworthy potential etymology, suggested by the LGPN-Ling, also deserves a mention : "Kyllaros" as a variation of Killaros (Κίλλαρος), and related to κιλλός (killos, "grey, donkey-colored").
Now, we've just established that that Cyllarus was a white horse, so wouldn't this be contradictory ? Well, not necessarily, no, since the majority of the "white" horses people know, including the famous ones from history or myth, would actually be grey horses that turned white over time, not true white horses. So, technically, it could still track...!
But anyway... Now that we've clarified everything about Cyllarus' name, his origins, even his color... One final question remains.
Is Cyllarus in the constellation Equuleus ?
(The constellation Equuleus.)
There doesn't seem to be any text from ancient Greece or Rome saying "the horse Cyllarus became the constellation next to Pegasus".
However, there is precedent in Roman literature for Cyllarus being placed among the stars. Martial writes :
"Quem pius astrifero Cyllarus ore bibit"
(Whereof trusty Cyllarus, now amid the stars, once drank) — Martial, Epigrams, book VIII.28 (1st century AD)
Here, the word astrifer (star-bearing) is used. One could be tempted to interpret it literally, with Cyllarus simply being a "star-bearer" as he's ridden by the Dioscuri. However, this very example is directly quoted in the definition of the word astrifer in Egidio Forcellini's Latin dictionary, for the second meaning of the word ("being put in the stars"). An idea which seems to be supported in another epigram, where Martial alludes to Cyllarus being in the constellation of his owners, the Ledean Twins (i.e. Gemini) :
"Ledeao poteras abducere Cyllaron astro : Ipse suo cedet nunc tibi Castor equo."
(Thou mightest have withdrawn Cyllarus from Leda's constellation ; Freely will Castor now yield his steed to thee) — Martial, Epigrams, book VIII.21 (1st century AD)
So, picturing Cyllarus in a constellation isn't necessarily ahistorical...!
When did they start to be associated with each other ?
The earliest common denominator between the constellation Equuleus and Cyllarus appears to be Philipp von Zesen's Coelum Astronomico-Poeticum. This work became the source of the 18th century texts about the constellation, including the erroneous detail of Cyllarus being a gift from Mercury.
(Philipp von Zesen.)
Zesen directly mentions "Cyllarus" among the names for Equuleus. He adds :
"Videtur autem esse Cyllarus, hoc est, equus ille, quem Mercurius Castori dederat dono : cujus mentionem ingerit Virgilius Georgic. l. 3 :
Talis Amyclei domitus Pollucis habenis Cyllarus, & cuorum Graji meminere Poëtae
Atque ad hanc opinionem inducor, quod videam equum stellatum olim Romae in aede Castoris dedicatum fuisse ; ut ad Signum Geminorum diximus."
(It seems, however, to be Cyllarus, that is, the horse which Mercury had given to Castor as a gift ; which Virgil mentions in the Georgics, Book 3 :
"Such was Cyllarus, tamed by the reins of Amyclean Pollux, and those whose fame Greek poets recount"
And I am led to this opinion, inasmuch as I see that the starry horse was once dedicated in Rome at the Temple of Castor ; as we have said regarding the sign of Gemini.) — Philipp von Zesen, Coelum Astronomico-Poeticum (1662)
Indeed, in the Gemini section of the book, Zesen had previously referenced it, writing : "Et in Romae in Aede Castoris ad Forum dicatus erat equus stellatus" ("And in Rome in the Temple of Castor at the Forum, a starry horse was dedicated"). We can, in turn, trace this phrasing back to Matthäus Rader's commentary on Martial, published in 1602.
Like we established earlier, Martial writes about Cyllarus being in the stars, which is probably what Rader is referencing when he describes him as a "starry" horse. There are no Roman sources mentioning anything about a starry Cyllarus being in the Temple of Castor (the closest to that is the fact that there used to be a stone, said to bear the hoofprint of the horse of Castor, near the lake Regillus, and venerated as such).
We can however still deduce that Cyllarus was represented, in some way or another, at the Temple of Castor, as Statius directly pictures him and says his name when he mentions the temple (while discussing the imposing equestrian statue of Domitian, erected not far from there) :
"...et pavet aspiciens Ledaeus ab aede propinqua Cyllarus."
(...and Leda's Cyllarus trembles as he looks from his neighboring shrine.) — Statius, Silvae (1st century AD)
But that's all there is on the topic, there's no direct connection linking a specific representation of Cyllarus in that temple to the stars.
Other candidates for the constellation
While Cyllarus is Zesen's first mythological pick for Equuleus, further down, he lists various horses from mythology whom he feels could also fill that role.
First, seemingly humorously, the horse from a legend about the emperor Trajan (in which Trajan's son rides a horse recklessly, killing a the son of a woman, who then demands justice to Trajan, and receives from the emperor his own son, the culprit, to adopt and replace the one she lost, alongside rich presents). Zesen explains this choice by saying that Equuleus looks like it's hiding behind clouds, as if guilty of a crime.
He then nominates two potential candidates from mythology :
The horse Saturn turned into to hide his affair with Phylira from his wife (which Zesen justifies by pointing out that the constellation Cygnus is about a similar story).
A horse placed in the stars by Neptune, maybe even the first horse, born when the god struck the ground during the contest for the patronage of Athens. He calls this horse "Scyphius".
We do find the name Σκύφιος (Skyphios) in Greek in some scholia (the Scholia to Lycophron 766 and the Scholia to Pindar, Pythian IV.246), albeit with a slightly different origin : the god Poseidon falling asleep on a rock and orgasming in his sleep, fertilizing it and creating Skyphios, the horse born from a rock.
(Ancient coin from Orthe in Thessaly, showing a horse emerging from a rock on which an olive tree grows.)
Zesen also praisingly mentions Bucephalus, the warhorse of Alexander the Great, then notes that if one were to make an interpretation of the constellation based on the Scripture, it would be the horse on which Haman placed Mordecai in the Book of Esther.
Later texts sometimes mention Bucephalus in their sections about Equuleus as a result.
In conclusion
Zesen's work profoundly influenced the perception of Cyllarus as Equuleus : the 1659 edition of Aegidius Strauch's Astrognosia doesn't mention anything about Equuleus apart from its name and its stars, with a laconic "Eum a Pegaso habere nomen, palam est" ("it is well known that it takes its name from Pegasus")... However, the 1668 edition is expanded and updated to quote Zesen's Coelum Astronomico-Poeticum, now mentioning Cyllarus, Bucephalus and the Biblical horse instead.
Thich is proof of the direct influence of the Coelum on later works, as star atlases start to mention Cyllarus and these mythical mythical horses after that point. Therefore, we can reasonably consider the origin of Equuleus as the horse Cyllarus/"Celeris" to be from there.
The writings of Zesen, a Baroque poet, about Cyllarus, even inspired other Baroque writers, such as Emanuele Tesauro, who wrote poems about the constellations. To conclude this very long post, here's, as parting words (and with a tentative translation), the poem he wrote for Equuleus, which he titled "Equus Minor, sive Cyllarus. / A Polluce insessus." ("The Lesser Horse, or Cyllarus / Ridden by Pollux.") :
Fraterno ut junxit Pollucem Jupiter Astro; Te Quoque Sidereis, Cyllare, junxit Equis. Atque ibi, tot sessum stadiis, bellique cruentum Pulvere, cum Domino te quoque nectar alit. Turpe est emeriti Senium non pascere Servi : Non eget hoc Dominus, ast eget hic Domino.
(As Jupiter joined Pollux to his brotherly star, So he joined you too, Cyllarus, to the starry steeds. And there, having been ridden through so many racecourses, and in the bloody dust of war, Nectar nourishes you too alongside your master. It is shameful not to feed the old retired servant : The master needs it not, but the latter needs the master.) — Emanuele Tesauro, Il cannochiale aristotelico (1663)
In summary (TL;DR)
There's no ancient Greek or Roman myth about a horse named Celeris. This was a 19th century misunderstanding, misspelling the name Cyllarus (and likely mixing it up with the Latin word celeris).
That horse was not given to the Dioscuri by the god Mercury (Hermes). It was also not the son of the Harpy Podarge. This is a confusion with other horses of the Dioscuri, Harpagus and Phlogeus. The horses Cyllarus and Xanthus were given by Juno (Hera). She herself is sometimes said to have received the horses from Neptune (Poseidon).
That horse was not the brother of Pegasus. This comes from a 19th century misinterpretation of a verse from Ovid about Chrysaor.
The horse Cyllarus is not black. This comes from a 19th century misinterpretation of a verse from Ovid about the centaur named Cyllarus. The horses of the Dioscuri are consistently represented as white.
"Cyllarus" does not mean "swift" or "from the city of Cilla". The name κύλλαρος (also written σκύλλαρος), meant a type of crab, hermit crab. It could also possibly be a name linked to κιλλός (grey, donkey-colored).
While there is some evidence in Roman literature of the horse Cyllarus being among the stars, none mention him being in Equuleus. There's no ancient myth explicitly associated with this constellation.
However, we can see interpretations of Equuleus as a representation of Cyllarus in 17th and 18th century texts, a Baroque creative trend likely started by Philipp von Zesen mid-17th century.
