Chapter 28: Comets and shooting stars

On comets, shooting stars, and similar phenomena.⁸³⁹

1a ⟨Aëtius⟩: Periodic stars and reflection

Some Pythagoreans say that a comet is a star belonging to those which are not always visible but rise periodically at a definite interval. Others held that it is a reflection of our sight toward the sun, resembling appearances in mirrors.⁸⁴⁰

1a ⟨Aëtius⟩: Anaxagoras and Democritus

Anaxagoras and Democritus held that it is a conjunction of two or more stars whose radiance combines.

1a ⟨Aëtius⟩: Aristotle

Aristotle held that it is an incandescent formation of the dry exhalation from the earth.⁸⁴¹

1a Comets and bearded stars

[Gap in the text.] They are comets when the material is kindled more extensively and lasts for a longer time, with the star appearing below and the hair shining above; they are bearded stars when, conversely, the star is seen above and the hair below, its shape giving the appearance of a beard.⁸⁴²

1a ⟨Aëtius⟩: Strato

Strato held that it is the light of a star enclosed in a dense cloud, as happens with lamps.

1a ⟨Aëtius⟩: Heraclides of Pontus

Heraclides of Pontus held that it is a cloud aloft, illuminated by light aloft. He gives a similar explanation of a bearded star, beams, a pillar, and related phenomena: as indeed do all the Peripatetics, he holds that these arise from the shapes assumed by the cloud.⁸⁴³

1a ⟨Aëtius⟩: Three further accounts

Epigenes held that it is an upward rush of wind mixed with earth and set on fire.

Boethus held that it is an appearance of ignited air.

Diogenes held that comets are stars.⁸⁴⁴

1a ⟨Aëtius⟩: Shooting stars and sparks

Anaxagoras held that the so-called shooting stars fall from the aether like sparks, and for this reason are extinguished at once.

Metrodorus held that the sun’s violent impact upon the clouds often produces sparks.⁸⁴⁵

1a ⟨Aëtius⟩: Xenophanes

Xenophanes held that all such phenomena are formations or movements of clouds set on fire.⁸⁴⁶

1b The Chaldean account

The Chaldeans are said to understand comets in this way: there are other stars besides the visible planets. For a time they are invisible because they travel somewhere very far above us; but they have also been seen after descending, as though strangers had been brought into the universe. Those who do not know that these too belong to the multitude of stars like to call them comets. They seem to disappear when they are carried back up to their own region, sinking into the depths of the aether as fish sink into the depths of the sea.⁸⁴⁷

1b Earthy material carried aloft

Others supposed that certain earthy materials are carried by winds or a tempest into the upper air. Set on fire and caught in the whirl of the aether, they revolve with the universe for a time; then, consumed by the fire, they become invisible. These are the stars called comets.⁸⁴⁸

1b The account attributed to Democritus

The account attributed to Democritus is that comets seem to form through the mutual reflection of the wandering stars with one another and with the fixed stars, just as star-like images have sometimes been seen when several mirrors reflect into one another.⁸⁴⁹

2 Arrian: Persistent appearances

Arrian says: “Those which remain for a time, some carried along in a fashion with the heavens, others wandering on a course of their own, are comets, torches, bearded stars, jars, and beams, each receiving its name from a resemblance in shape.”⁸⁵⁰

2 Arrian: Duration and destruction

[Gap in the text.] “Evidence is the fact that they do not perish at once: if they formed in the air, they would be quickly extinguished in its cold. That they are temporary is shown by their destruction.⁸⁵¹

2 Arrian: A damaged argument about the north

And the fact that they form more toward the north than in another region of the heavens also bears upon this: there the air is thicker and formation is not easy; to be carried toward the ... [text corrupt].⁸⁵²

2 Arrian: Movement and nourishment

Most comets move irregularly, feeding, as it seems to me, on the nourishment carried upward and following its course.⁸⁵³

2 Arrian: The head and its hair

Their head is star-like, since everything of a fiery nature tends to gather into a sphere. Their hair is like a ray of light: in some it spreads loosely, as though unbound; in others it runs straight and stretches somewhat upward from the star.⁸⁵⁴

2 Arrian: Jars and fringed fixed stars

Jars have appeared only rarely, since they require a greater gathering of fire. Some of the fixed stars too have appeared with hair, when ⟨the⟩ rising air around them, becoming dense, produces an image of hair attached to them, just as halos appear attached to the stars themselves.⁸⁵⁵

2 Arrian: Visibility near the sun

Some comets formed near the sun have disappeared before their coming into being became visible. Others have come into view during an eclipse of the sun, and others while setting after it, having previously, as one would expect, been overwhelmed by its rays, so that they were not visible.⁸⁵⁶

2 Arrian: The proposed physical explanation

Thus the account ⟨which⟩ declares the following would prevail: compacted masses of air are squeezed out and fall into the lower parts of the aether adjoining the air; once kindled, they persist and revolve with the aether for as long as nourishment remains around them.”⁸⁵⁷

2 Names derived from shapes

Each of these receives its name from whatever shape it happens to have: comets, when a radiance of fire shines out all around like hair; bearded stars, when the radiance hangs to one side in the shape of a beard; jars, when the appearances are large and circular and display some depth within themselves; and beams and torches, from their resemblance in form to the things ⟨after which⟩ they are named.⁸⁵⁸

2 Arrian: Evening and morning appearances

“Each of these appears both in the evening and in the morning; some also appear at both times. They call those visible at both times which, after appearing toward the west at the beginning of the night, have risen again during that same night, before daylight arrives.”⁸⁵⁹