Comets


‘From the beginning of the world, those stars called comets have been held to be the greatest of all wonders seen in the heavens. All philosophers of every age have been much concerned to know the origin, nature, and attributes of such stars, since they are not always visible in the heavens, but only at certain times, and thereafter expend themselves. Various opinions have been expressed by ancient and modern philosophers concerning comets and their origin, the first of which was held by Pythagoras and his followers, Democritus and Anaxagoras, that comets are born in the heavens and are special stars which arise at times and then come so near the earth that they can be seen by us men, and then are charmed away from us again into the heights, and have their being and place in the heavens. But Aristotle, who came after them, has refuted and defeated their arguments, for he was of the opinion that no alteration nor any change occurred in the heavens, and also that nothing new could be born there...’

Tycho Brahe’s German Treatise on the Comet of 1577.*


The comet of 1577, with the nova in Cassiopeia of 1572, are often cited as the two deathblows to the aristotelian cosmos, already under attack since Copernicus’s publication of his De revolutionibus in 1543. Certainly Tycho Brahe, in both his German treatise written for King Frederic II of Denmark, and his subsequent major publication on the comet of 1577, De Mundi Aetherei Recentioribus Phaenomenis (Uraniborg, 1588), was adamant that Aristotle had been disproved. His observations of the comet’s parallax as being smaller than the parallax of the moon clearly demonstrated that the comet lay beyond the moon, in the place where Aristotle had stipulated that ‘nothing new could be born there’. But just because Brahe had proved that Aristotle was wrong did not mean that the rest of Europe followed suit. As Hellman argues (1963), Brahe's work on comets was only one of a number of authors writing on comets and not all agreed with his anti-aristotelian conclusions. As Lattis (1994) relates, the Jesuit astronomer Christoph Clavius did not even mention it in any of his editions of his renowned commentary on Sacrobosco. The appearance of the 1577 comet was indeed seminal for early modern astronomy but to conclude that it automatically brought about the collapse of the aristotelian order would be to ignore the longevity of aristotelianism in its many forms. As Ariew (1992) reminds, aristotelian notions about comets were alive and well as late as the early eighteenth century as the work of Du Hamel testifies.

Edward Worth collected seminal works on astronomy by all of these authors but without doubt the pride of place in his collection on comets was Johannes Hevelius’s Cometographia, which Van Nouhuys (1998) rightly states was ‘the first systematic step in the historiography of comets’.

 

 
Johannes Hevelius, Cometographia (Danzig, 1668), title page.

 


It is not hard to see why Worth purchased the Cometographia: Hevelius depicted every aspect of comets he possibly could – in many cases making the engravings himself. Brahe had been anxious to chart the path of the 1577 comet for Frederic II of Denmark in words but Hevelius provides wonderful illustrations to show exactly where a comet is at any one time. Here we see his illustration of the path of the comet of 1652 through the various constellations:

 

 
Johannes Hevelius, Cometographia (Danzig, 1668), Fig. A.

 


Again, in Figure LL we see a charting of the 1661 comet using the same method:

 

 
Johannes Hevelius, Cometographia (Danzig, 1668), Fig. LL.

 


This anthropomorphic approach was matched by far more technically acute diagrams: here we see Hevelius’s depiction of the comets observed by Johannes Kepler and Christen Sørenson Longomontanus in 1607 and by Johann Baptist Cysatus in 1618.

 

 
Johannes Hevelius, Cometographia (Danzig, 1668), Fig. AA.



The technical excellence of Hevelius’s treatment is all the more intriguing when we compare his illustrations with those of the Theatrum cometicum published in the same year at Amsterdam by Stanisław Lubieniecki, 1623-1675, another Polish commentator on comets whose work was likewise collected by Worth.

 

 
Stanisław Lubieniecki, Theatrum cometicum (Amsterdam, 1668), frontispiece portrait.

 


As this portrait of the author makes plain, Lubieniecki was a clergyman and, unlike Hevelius, not primarily an astronomer. Rather he came to comets through his interest in church history. In effect his Theatrum cometicum was an investigation of comets from the Flood up to his own time. This mixture of astronomy and biblical chronology finds echoes elsewhere in Worth’s collection: Arthur Bedford’s This scripture chronology demonstrated by astronomical calculations and also by the year of jubilee and the jewish sabbat (London, 1730). Indeed, the interaction of astronomy and religion also runs through the work of Newton’s successor as Lucasian lecturer, William Whiston’s Astronomical principles of religion, natural and reveal’s (London, 1717).

Lubieniecki’s illustrations are lively but essentially crude depictions when compared with those of Hevelius. In the following illustration we see Lubieniecki’s attempt to show the development of a comet, seen at Cologne on the 13 December 1665:

 

 
Stanisław Lubieniecki, Theatrum cometicum (Amsterdam, 1668), plate no. 1.

 


But to discount Lubieniecki completely on the technical expertise of his illustrations would not be totally fair. Sometimes he produces useful little touches to his rather chaotic pictures. An example of this may be seen in his fourth plate where he includes a table of the magnitude of stars to the left of the constellation Orion:

 

 
Stanisław Lubieniecki, Theatrum cometicum (Amsterdam, 1668), plate no. 4.

 

We see him using a similar device in his 31st plate:

Stanisław Lubieniecki, Theatrum cometicum (Amsterdam, 1668), plate no. 31.

 

Comet tails

Lubieniecki concentrated in his many illustrations on tracking the path of a comet through the constellations and paid relatively little attention to that subject which fascinated other writers on comets: comet tails. Indeed, he only includes illustrations of them in his first plate of the 1665 comet sighting at Cologne. Hevelius, on the other hand, provides us with an earlier attempt to distinguish between comet tails:

 

 
Johannes Hevelius, Cometographia (Danzig, 1668), Fig. K.



He also attempts to show tails in chronological order, starting with Brahe’s 1577 comet at the top of the page:

 

 
Johannes Hevelius, Cometographia (Danzig, 1668), Fig. L.



Brahe characteristically drew attention to the fact that the tail of the 1577 comet disproved Aristotelian notions:

‘... at all times this comet had its tail turned directly away from the sun, as all other comets, those observed many years ago by Regiomontanus, Apian, Gemma Frisius, and Fracastoro, have also done: all have turned their tails away from the sun. From this, it appears that the tail of a comet is nothing but the rays of the sun which have passed through the body of the comet... Therefore, Aristotle and all those who follow him cannot maintain their opinion, namely that the tail of a comet is a flame of the rare fattiness which is burning above the air, for if that were true, these flames would not have a relationship to the sun, and always turn themselves away from it...’*


Brahe may have failed to take into account the effect of the solar orbit on comets but, as Thoren relates (1990), he was slowly working his way towards an understanding of the 1577 comet which would disprove the aristotelian cosmos in a more fundamental way: when Brahe initially sighted it in the second week of November 1577, he noticed that it was moving very quickly in front of the sun but that in the following weeks its speed appeared to fall off as it moved further away. His conclusion: the comet was, in fact, orbiting the Sun. The 1577 comet, just as the 1572 nova, has become synonymous with the name of Tycho Brahe but, as Van Nouhuys (1998) suggests, instead of the 1577 comet making Brahe famous, we should perhaps think of it the other way around: Brahe made the 1577 comet unique. There had been sightings of earlier comets which had suggested that they began life in the supra-lunary realm but it was only with Brahe’s accurate measurements of parallax that the matter could finally be decided.

 

 
Stanisław Lubieniecki, Theatrum cometicum (Amsterdam, 1668), plate no. 32.

 

Selected Reading:

*All excerpts from Brahe’s treatise on the 1577 are taken from this source: Christianson, J. R. (1979). ‘Tycho Brahe’s German Treatise on the Comet of 1577: A Study in Science and Politics’, Isis 70, no. 1, 110-140.

Ariew, R. (1992). ‘Theory of Comets at Paris during the Seventeenth Century’, Journal ofthe History of Ideas, 53, no. 3, 355-372.
Hellman, C. D. (1963). ‘Was Tycho Brahe as influential as he thought?’, The British Journal for the History of Science, 1 no. 4, 295-324.
Lattis, J. M. (1994) Between Copernicus and Galileo. Christoph Clavius and the Collapse of Ptolemaic Cosmology. Chicago: University of Chicago Press.
Thoren, V. E. (1990). The Lord of Uraniborg. A biography of Tycho Brahe. Cambridge: Cambridge University Press.
Van Nouhuys, Tabitta (1998). The Age of the Two-Faced Janus. The Comets of 1577 and 1618 and the Decline of the Aristotelian World View in the Netherlands. Leiden: Brill.