Back in 2020, when I wrote a piece about ancient Greek colour terms, two comments raised an interesting side-question: what colour was the star Sirius in antiquity?
|Did Sirius look red to ancient astronomers? First, be warned that the colours above aren’t real. Colours in space photos are always heavily enhanced — or, as in this picture, totally fake.|
Sirius is the brightest star in our night sky. In antiquity it was also known as the Dog star; it still is today. It looks white. Or maybe blue-white: its spectrum has its peak at blue frequencies, and photographs tend to create blue halos. But really Sirius floods the entire range of visible light.
Over the last 250 years a question has been simmering, because — supposedly — some ancient writers describe it as ‘red’. Astronomers want to know: is it even possible that Sirius changed colour between the 100s and the 1700s CE?
The modern debate
But, to this rule there seems to be one exception, and that in a remarkable star: for old authors mention the Dog star, which is now white, and not at all inclined to redness, as being then very much so; as in the following places: ...
Barker 1759: 499
The colour change theory was first proposed in 1759 by Thomas Barker, an English country squire, meteorologist, and astronomer. He cited several pieces of ancient testimony, looking directly at the Greek and Latin terminology in each case:
- Aratos, Phainomena 326–328 (3rd cent. BCE): the Dog star is ποικίλος (poikílos).
- Cicero, Aratea fr. 34.107–108 ed. Pellacani (1st cent. BCE): the Dog star ‘shines with rutilus light’ (rutilo cum lumine claret).
- Horace, Satires 2.5.39-40 (1st cent. BCE): refers to rubra Canicula.
- Seneca, Quaestiones naturales 1.1.7 (1st cent. CE): refers to the rubor of Canicula.
- Ptolemy, Almagest 7.5, 142 ed. Heiberg (2nd cent. CE): ‘the star in the mouth [of the Dog constellation, i.e. Canis Major] is the brightest, called the Dog; it is ὑπόκιρρος (hypókirrhos)’.
- Hyginus, Astronomica 2.35 (1st cent. BCE/CE): refers to the ‘brightness’ or ‘whiteness of its flame’ (flammae candorem); Barker thinks (1) candor means strictly ‘whiteness’; so (2) this reference ‘expressly contradicts’ the others; so (3) Hyginus should be disregarded.
You’ll notice I’m leaving some Greek and Latin terms untranslated. That’s because their meaning is precisely what we’ll explore below.
I won’t cover the full history of the debate, which was argued by astronomers such as Jérôme de Lalande, Theodor von Schubert, and John Herschel. For the full story, see Ceragioli (1995).
One key development was in 1850, when Alexander von Humboldt published volume 3 of his book series Kosmos. Humboldt delved into the philology of the terms used by the ancient writers, with special attention to Ptolemy’s colour term, hypókirrhos.
The expression ὑπόκιῤῥος, which Ptolemy employs indiscriminately to designate the six stars named in his catalogue [i.e. the six stars named as hypókirrhos], implies a slightly marked transition from fiery-yellow [feuergelb] to fiery-red [feuerroth]; it therefore refers, strictly speaking, to a fiery-reddish colour. ... Κιῤῥός is, according to Galen, (Meth. med. 12,) a pale fiery-red inclining to yellow. ... Sirius is said by Seneca (Nat. Quæst., i. 1) to be redder than Mars ...
This report of the terminology is still widely treated as authoritative, because astronomers don’t typically learn Latin and ancient Greek these days. But as we’ll see, Humboldt is entirely wrong.
Roger C. Ceragioli, who trained as a classicist, wrote a 1995 article covering the modern debate and exposing the deluge of misinformation. Ceragioli handily disposes of most of the supposed evidence for ‘red Sirius’, but he thinks Barker’s references to Ptolemy, Horace, and Seneca stand up.
There is no doubt about what Ptolemy means. He bluntly says ‘reddish’ and other ancient sources corroborate him ...
Ceragioli 1995: 187
As a result, they still need explanation: either it’s because Sirius scintillates in various colour-flashes when close to the horizon (Ceragioli 1995), or because hypókirrhos in Ptolemy is an interpolation (Ceragioli 1996).
|Note. The only other substantive discussion of the matter by a modern classicist that I’ve found is by Pellacani (2015: 156–157), who is much more willing to indulge the ‘red Sirius’ theory, is unaware of Ceragioli’s articles, and is selective in his reading of another key source, Avienius. We’ll return to Avienius below.|
In fact none of the supposed evidence for ‘red’ Sirius stands up to scrutiny:
- Hypókirrhos doesn’t mean ‘fiery red’ or ‘reddish’: it means ‘pale yellow’.
- Horace’s and Seneca’s rubor primarily denotes ‘heat’. Its meaning as a colour term, ‘red’, is uncommon.
- Cicero’s word rutilus primarily means ‘bright, shiny’, especially when used of celestial bodies. And anyway, when he uses the word he’s not talking about Sirius.
|In fiction, Sirius is usually shown as noticeably blue to the naked eye. (Elite Dangerous, 2014)|
For modern advocates of ‘red Sirius’, Ptolemy’s testimony carries the most weight.
ὁ ἐν τῷ στόματι λαμπρότατος καλούμενος Κύων καὶ ὑπόκιρρος ...
Constellation of Canis (Major).
The (star) in the mouth (of the Great Dog); the brightest; called the Dog; and hypókirrhos...
Hypókirrhos is ‘somewhat kirrhós’. But neither hypókirrhos nor kirrhós means ‘red’. A more correct translation is ‘cream, light yellow’.
Hypókirrhos and kirrhós are very rare words in most contexts. In extant classical-era texts (5th–4th century BCE) they appear only twice, both in the Hippokratic corpus. The etymology is unknown. Even at the best of times, interpreting Greek colour terms is tricky: here, extreme caution is needed.
The argument for interpreting hypókirrhos as ‘reddish’ rests entirely on these two points:
- Ptolemy describes six stars as hypókirrhos: Arcturus, Aldebaran, Pollux, Antares, Betelgeuse, and Sirius (Almagest 7.5: pages 50, 88, 92, 110, 132, and 142 ed. Heiberg). Of these, Aldebaran, Pollux, Antares, and Betelgeuse are noticeably golden or orange-ish to the naked eye.
- According to Humboldt, a passage in Galen defines kirrhós as ‘a pale fiery-red inclining to yellow’ (ein blasses Feuerroth, das in Gelb spielt; Galen, De methodo medendi book 12, x.832 ed. Kühn).
Humboldt cherry-picks his Galen, and even the passage he cites has problems. Galen’s exact words are
εἰ δ' ἄλλως ἐθέλεις ὀνομάζειν τὸ κιρρὸν χρῶμα, δύναιο ἂν λέγειν πυρρὸν ἢ ὠχρόν.
If you want to refer to the colour kirrhós differently you could say pyrrhós or ochrós (‘pale’).
In the 19th century, dictionaries treated pyrrhós as referring straightforwardly to pŷr ‘fire’. Humboldt seems to have in mind Pape’s definition (1st edition 1842):
feuerfarben, feuerroth, röthlich, in verschiedenen Abstufungen der Farben, bis zum Blonden hin ...
fire-coloured, fiery red, reddish, in various colour grades ranging to blonde ...
(Cf. Passow: ‘feuerfarb, feuergelb, feuerroth, goldgelb, überh. röthlich’.) In fact the exact linguistic relationship between pyrrhós and pŷr is unclear (Beekes 2010: 1264). Even to the extent that they’re connected, fire ... um, isn’t red.
Evidence from ancient usage of pyrrhós is a mixed bag. A pseudo-Aristotelian work implies a link to the colour of foxes; one late lexicographical source treats pyrrhós as a synonym for erythrós. Then again, another late lexicographical source defines erythrós as mélas, and pyrrhós as xanthós, keeping them as two separate colour categories. And Plato says pyrrhós is what you get if you mix xanthós (‘golden’) and phaiós (‘grey’) pigments.
The point is, there’s nothing simple about this.
|Note. Ps-Aristotle, Physiognomonica 812a (xanthós-haired people have a bold spirit like lions, pyrrhós -haired people are villainous like foxes); Hesychios 6084, ii.201 Latte (ἐρυθραίνετο· ἐρυθρά ἐγένετο, πυρρά); Souda ε.3101 (ἐρυθρόν· τὸ μέλαν; similarly ε.3092), π.3235 (πυρρός· ὁ ξανθός); Plato, Timaios 68c. I am grateful to @SartrixMartiana and @oliveratlantis for pointing out the ps-Aristotle, Hesychios, and Souda examples to me. The new Cambridge Greek lexicon (2021) avoids ‘red’ in its definition of pyrrhós, except — paradoxically — when used of gold. The same lexicon omits kirrhós altogether.|
Back to kirrhós. Setting aside Humboldt’s Galen passage, other contexts don’t support ‘red’. The most common use of kirrhós, in fact, is for a colour of wine — and it is not red wine.
Kirrhós wine is a white wine with relatively heavy colour: think chardonnay rather than pinot gris. It is invariably opposed to red wine, which is called mélas (‘dark red, deep brown, black’; mélas is also regularly used of blood).
Bear in mind that wine wasn’t backlit in antiquity. Ancient wine-drinkers saw their wine in the bottom of a ceramic kylix, not through the side of a transparent glass. This may help explain why they called ‘red’ wine mélas. A wine would have to be very pale to look erythrós (‘red’) in a kylix — more like a rosé.
Instead of kirrhós wines, use red ones [mélasin] ...
ps-Hippokrates, De mulierum affectibus 115
Wines are white [leukós], kirrhós, or red [mélas]. ... And Mnesitheos of Athens says: ‘Red wine is very good for growth. White wine is a very good diuretic, and is the thinnest. Kirrhós wine promotes dryness, and is good for digesting food.’
(= Mnesitheos fr. 46 ed. Bertier)
... keep watch on the testing of the wines, and always choose the one lightest in substance — the colour that Hippokrates usually calls kirrhós. You could also call it golden [xanthós]. Pale [ochrós] is also good, in between golden and white. In fact if you want to mix golden wine with white, you will produce a combination of both that is pale ...
Galen, De sanitate tuenda vi.335
|Note. In Mnesitheos/Athenaios, ‘dryness’ (ξηρός) has nothing to do with the modern sense of a low-sugar wine: the word for that is αὐστηρός. See Boulay 2015: 277–279 on the vocabulary for the tastes of wine. ‘Dry’ here means foods that supposedly reduce phlegm, in the ancient medical theory of the four humours.|
Here Galen sorts ‘white’ wines by the intensity of their colours, ranging from leukós, to ochrós, to kirrhós or xanthós. That is, he groups kirrhós firmly among white wines. He expands the range to red wines elsewhere:
You won’t find any wine that is thick and sweet that isn’t red [mélas]. ... There is no sweet wine that is white [leukós], but some are dry [austerós] and thick, some watery and light. Golden [xanthós] and kirrhós wines are moderately sweet, like Hippodamanteian wine, and the Faustian Falernian. Some are not sweet at all. Light red [erythrós] wines are thicker than these, just as others are (thicker) than them, as they approach the reds [mélas] in colour.
Galen, De bonis malisque sucis
We can’t review kirrhós exhaustively. Galen uses the word over 100 times, far more than any non-medical writer. Almost every time it refers to wine. Let’s just highlight a few more sources that use kirrhós for things other than wine.
- A Hippokratic text (5th cent. BCE) describes the symptoms of a sick woman, and says her faeces were hypókirrhos.
- A fragment of Aristotle (4th cent. BCE) describes a fish as kirrhós, and the fragment is repeated elsewhere. But unhelpfully, the fish is of unknown species. (Liddell & Scott suggest it is a Labrus or wrasse, without basis.)
- An excerpt of a lost work by Aristophanes of Byzantion (3rd cent. BCE) states that the best milk is the thickest and ‘most kirrhós’; white [leukós] milk isn’t as nourishing.
- Dioskourides (1st cent. CE) says the best beeswax is hypókirrhos. Elsewhere he refers to three varieties of frankincense, one white [leukós], one hypókirros, and one ‘more kirrhós’; Frankincense is typically pale yellow.
- Galen (2nd cent. CE) refers to bitter vetch, acacia, and mastic as kirrhós. Acacia is yellow; mastic is pale yellow. Bitter vetch flowers are lilac, but since he’s talking about consuming it roasted, he must be talking about the seeds, which are yellow. (Another less helpful passage says that kirrhós is synonymous with two dialectal words ... both of unknown meaning.)
- Aetios (6th cent. CE) uses kirrhós as a synonym for hypóxanthos, ‘somewhat golden’, and assigns various foods to that colour including wheat and chickpeas — that is, light yellow.
|Sources. ps-Hippokrates, Epidemics 7.11; Aristotle fr. 307 Rose = Athenaios 7.281f; Aristophanes, Historia animalium epitome 1.94; Dioskourides 2.83 (beeswax), 1.68 (frankincense); Galen, De remediis parabilibus xiv.366 Kühn (bitter vetch), xiv.533 (mastic, acacia), Glossary xix.129 (‘Zenodotos ... says the people of Sikyon refer to kirrhón as péllon’); Aetius i:proem = viii.1:29,18–21 ed. Oliveri.|
In short, Ptolemy does not call Sirius ‘red’. A safer translation would be ‘cream-coloured, pale yellow’. There may still be a question of why he calls it that when it’s clearly white, but at least ‘red’ is off the table. One of Ceragioli’s explanations may still be needed for the ‘pale yellow’.
|Photos reportedly taken in 2018 by Amanda Cross, an English amateur astronomer, using an out-of-focus camera to illustrate how a star’s colour varies when close to the horizon. Sirius is white when higher in the sky; the exceptional range of its colours close to the horizon lends support to Ceragioli’s argument. Source: EarthSky, March 2018.|
One final point I’d better address is another place where Ptolemy uses hypókirrhos, in the astrological Tetrabiblos. There he claims that solar eclipses effectively put a colour filter over the world; and he links each ‘filter’ to one of the five planets. Hypókirrhos is the colour he associates with Mars (Tetrabiblos 2.90).
But once again, this doesn’t imply ‘red’. If you look at the whole list, it’s obvious he isn’t describing the colours of the planets themselves:
||Associated colour in eclipses
||(1) μέλας (mélas) or (2) ὑπόχλωρος (hypóchloros)
||(1) black/dark red; (2) somewhat chartreuse
Jupiter looks white to the naked eye, so that works. But Venus only starts to look a bit yellowish if you have a really good telescope. And it’s hard to see Saturn as ‘black’ or chartreuse, or Mercury as ‘dappled’. The Tetrabiblos passage adds no new information.
|The sequel to The hundred and one dalmatians: Sirius, the Dog Star, addresses the dogs of the world from the top of Nelson’s Column and invites them all to come and live in space. Hey, man, it was the 60s. (Dodie Smith, The starlight barking , ch. 10)|
Roman sources: rubor and rutilus
With Roman writers, we don’t need to mess about with wine colours. As we saw earlier, Cicero says the Dog star ‘shines with rutilus light’; Horace refers to rubra Canicula ‘the red Dog star’; and Seneca refers to the rubor of Canicula. (Cicero, Aratea fr. 34.107–108 ed. Pellacani; Horace, Satires 2.5.39-40; Seneca, Quaestiones naturales 1.1.7.)
And rutilus, ruber, rubor certainly mean ‘red’ — in terms of their etymology, anyway. They’re cognate with Greek erythrós ‘red’, Sanskrit rudhirá- ‘red, bloody’, and Germanic rot, rood, red. Rubor regularly refers to blushing and inflammations. So at first sight, it does look like there’s a legitimate case for ‘red Sirius’ here.
First we’d better set aside one doubt about the Horace and Seneca: Canicula ‘small dog’ can also refer to Procyon, the most prominent star in Canis Minor, the ‘little dog’. Prokýon is in fact Greek for ‘dog in front’. And a recent scholarly commentary specifically identifies Horace’s Canicula as Procyon, not Sirius (Freudenburg 2021: 210). But I’m going to say that we’d better not assume that’s right. First, Procyon also looks white. Second, Sirius was proverbial in antiquity for scorching heat, rising as it does in the ‘dog days’ of summer, so Procyon should never be the default interpretation. For now at least, let’s assume there is a real question over Sirius.
The more substantive problem is that, though the words are etymologically linked to ‘red’, and though these words can sometimes mean ‘red’, they hardly ever actually refer to a literal hue. To illustrate, here’s the earliest attested appearance of rubor in Latin:
frigit saetas rubore ex oculis fulgens flammeo.
His hair roasts, he shines a flaming rubor from his eyes.
Accius, Meleager fr. 4
The metaphorical meaning ‘heat’ is much more salient here than a literal red hue.
And this isn’t a one-off. I’ve checked all appearances of rubor before the 1st century CE, and a few references in the 1st century, and only once does rubor refer to a literal hue. Its primary meaning is ‘shame, modesty’. Additional senses include ‘fiery heat’ (Accius, above); in the medical writer Celsus, it can mean either ‘blush’ or ‘inflammation’; once Cicero uses it for a blush cosmetic, evoking ‘shame’ still more metaphorically. And once, and once only, Vergil uses it to refer to a literal colour: the rubor of Tyrian dye.
|Note. rubor = ‘shame, modesty’: Plautus, Captivi 962; Publilius Syrus R 8 (= 576 ed. Woelfflin); Catullus 42.16, 65.24; Cicero, De oratore 2.242, Topica 52, De re publica 4.6 fr. 1, Tusculae disputationes 4.(8).19, De natura deorum 1.(27).75, fr. 15.2; ps.-Cicero, Ad Herennium 4.(10).14; Tibullus 2.1.30; Vergil, Aeneid 12.66. rubor = cosmetic, standing for shame: Cicero, Orator (23).79 (‘let all cosmetics of candor and rubor be abolished (from oratory)’). rubor = ‘blush, inflammation’: Celsus, frequently. rubor = red dye: Vergil, Georgics 3.307.|
Some of these things are (or can be) literally red, but the real theme connecting the primary meanings — ‘shame, blush, inflammation’ — is heat. Fire, an embarrassed blush, and an inflammation are each hot; Vergil makes it even clearer, with a rubor running through someone’s ‘heated face’ (rubor et calefacta per ora cucurrit).
In short, the most common meaning of rubor is actually ‘heat’. And for Sirius that makes perfect sense. Remember, Sirius was and still is proverbial for the scorching heat (or ‘dog days’) of midsummer.
In Seneca, the context is that he’s paraphrasing a discussion by Aristotle of atmospheric phenomena, explaining that ‘fires’ in the sky, such as comets, are caused by ‘evaporations’ from the earth, and these evaporations manifest as different phenomena depending on their heat. Seneca then gives Sirius, Mars, and Jupiter as celestial parallels to the terrestrial phenomenon. And he straight-up tells us that while Jupiter converts its brightness into ‘pure light’ without heat, in Sirius’ case it becomes rubor.
As for Horace, unfortunately, we have no context. His reference to rubra Canicula is a quotation from another poet, Furius Bibaculus, whose works have been lost.
|Note. Seneca’s discussion is paraphrased from Aristotle, Meteorologica 341b; the reference to Sirius is Seneca’s own insertion. On Horace’s quotation of Furius, see Freudenburg 2021: 210–211.|
We have one last ‘red Sirius’ passage to deal with. It’s in the fragments of Cicero’s Aratea, a Latin translation of Aratos’ Greek poem the Phainomena. Aratos’ Phainomena is a poem about astronomy, dating to the 3rd century BCE, which spends some time describing the major constellations.
Aratos himself doesn’t call Sirius ‘red’: he refers to the constellation as a whole as poikílos, ‘variegated’, in reference to the uneven brightness of its stars.
And behind [Orion’s] towering back, what a guardian
appears! A Dog walking on both his hind legs,
variegated [poikílos], however, not shining all over ...
... The tip of its
fierce chin is marked with a star which scorches [seiriáei]
more keenly than any other, and people call it
The ‘scorching’ is another reference to the midsummer heat associated with Sirius. Cicero turns this passage into:
For beneath [Orion’s] feet there shines with rutilus light
the fiery Dog, shining and reflecting the light of the stars. ...
But not from all its body does it breathe flame
and make summer fires burst out with its strong breath:
all the blazing shines from its mouth and is cast upon mortals.
Cicero, Aratea fr. 34.107–112 ed. Pellacani
Two points to observe here:
- Just like Aratos’ poikílos, Cicero’s ‘rutilus light’ refers to the constellation as a whole. Sirius itself is the star at the Dog’s mouth, the totus ... micans ... ardor in line 112.
- While rutilus is linguistically linked to ruber ‘red’, it is routinely used to describe stars. And when describing stars, it doesn’t mean ‘red’: it means ‘bright, shining’.
It’s instructive to compare what Avienius does with the same passage, in another translation of Aratos dating to the 4th century:
[The Dog] burns, studded with rutilantes stars,
but its intensity isn’t the same all over ...
... The heavy blazing flows from its chin,
and burns the aether under a terrible title: Sirius.
When the sun turns its rutilos poles that way,
what suffering threatens people’s bodies, threatens the fields!
Avienius makes it clearer that rutilans doesn’t refer to Sirius, but to ... well, every other star in the constellation. And in line 734, it’s the sun itself that has a rutilus axis, not Sirius.
Can we hammer the point home even harder? Oh, you betcha. Avienius mentions Sirius again later on:
Meton set the very start of the year at the season
when Phoebus’ rutilus star scorches Cancer,
when the sea carries away Orion’s belt,
when Sirius burns with its blue [caeruleo] star.
Here again it’s the sun that’s rutilus, ‘the star of Phoebus’. And Sirius is — well, what do you know. He calls it blue. How about that.
And that isn’t a one-off either. Another astronomical poem by Manilius (1st century CE) refers to it as ‘blue’.
A great assurance of [the Dog’s] power are its colour, and the twinkling
of fire in its mouth — hardly less than the sun, except that it’s fastened
far off. Cold are the beams it brandishes in its blue [caeruleo] face.
The paradox here isn’t that Manilius calls it blue, it’s that he calls Canis Major cold. For every other ancient author, Sirius is the symbol par excellence of midsummer sweltering.
To sustain ‘red Sirius’ on Greco-Roman evidence, you’d have to ignore all the metaphorical flavour of rubor, which was really its primary meaning; you’d have to throw away every reference to kirrhós wine, milk, beeswax, chickpeas, acacia, and so on. And you’d have to ignore the fact that when Avienius uses the word rutilus, he doesn’t use it to refer to Sirius, he uses it to contrast with Sirius.
As well as that, you’d have to imagine that Sirius was red when Horace and Seneca were active, in the 1st centuries BCE and CE, but it turned blue by the time Manilius was active, also in the 1st century CE. Then it turned red again for Ptolemy in the 2nd century, then blue again when Avienius came along in the 4th century.
Stuff and nonsense. No, Virginia, ancient Greco-Roman astronomers did not describe Sirius as red.
Pale yellow, maybe. And if you really want to push it, maybe you can make that a problem. But given that that’s based entirely on a single throwaway line in Ptolemy ... I don’t fancy your chances.
- Barker, T. 1759. ‘Remarks on the mutations of the stars.’ Philosophical transactions 51: 498–504. [JSTOR | Internet Archive]
- Beekes, R. 2010. Etymological dictionary of Greek. Leiden/Boston.
- Boulay, T. 2015. ‘Wine appreciation in ancient Greece.’ In: Wilkins, J.; Nadeau, R. (eds.) A companion to food in the ancient world. Oxford. 273–282.
- Ceragioli, R. C. 1995. ‘The debate concerning “red” Sirius.’ Journal for the history of astronomy 26: 187–226. [Sci-Hub]
- —— 1996. ‘Solving the puzzle of “red” Sirius.’ Journal for the history of astronomy 27: 93–128. [Sci-Hub]
- Freudenburg, K. 2021. Horace. Satires book II. Cambridge.
- Holberg, J. B. 2007. Sirius. Brightest diamond in the night sky. Chichester.
- Von Humboldt, A. 1850. Kosmos. Entwurf einer physischen Weltbeschreibung, vol. 3. Stuttgart. [Internet Archive]
- —— 1851. Cosmos. A sketch of a physical description of the universe (trans. E. C. Otté; English translation of the above). [Internet Archive]
- Jouanna, J. 2012 . ‘Wine and medicine in ancient Greece.’ In: Greek medicine from Hippocrates to Galen. Selected papers. Tr. N. Allies. Leiden. 173–193. Orig. publ. as ‘Le vin et la médicine dans la Grèce antique.’ Revue des études grecques 109.2: 410–434. [JSTOR]
- Pellacani, D. 2015. Cicerone. Aratea. Parte I: Proemio e catalogo delle costellazioni. Bologna.