The sheet
The thing at the centre of this is not a legend. It is an object, roughly 26 by 38 centimetres, printed in Nuremberg in 1561: a woodcut with a block of text beneath it, produced by a printer named Hans Glaser and sold in the streets. A hand-coloured copy survives in the prints and drawings collection of the Zentralbibliothek Zürich, and it has been digitised, so the primary document can be looked at directly rather than described.
That is unusual. A great deal of what circulates as historical evidence for visitors before the twentieth century is a paraphrase of a paraphrase. This is a dated artefact from the year of the event, and what it actually says is more interesting than the use it gets put to.
What it describes
Glaser's text reports that at dawn on 14 April 1561, between four and five in the morning, many men and women of Nuremberg saw a great number of shapes in the sky.
They came out of the sun. There were rods or beams, some of them red, some blue-black; there were spheres, described as blood-coloured, in groups of three and four; there were crosses. The shapes moved against one another for something over an hour — the account reads as a battle, with objects driving at each other and circling back. Then they appeared to fall to the earth as if burning, with a great smoke, and afterwards a long black spear-like shape was seen.
The sheet does not present this as a curiosity. It presents it as a warning from God, and closes by calling on those who read it to repent, mend their lives and pray for mercy so that the wrath it announces might be turned aside. That was the genre. Broadsheets of this kind were the period's news medium, and a celestial portent was one of the reliable things to print.
A comparable sheet records black spheres over Basel five years later, on 7 August 1566. The two are usually cited together, and they belong to the same tradition of printed prodigies.
That tradition matters for reading either of them. The single-sheet broadside was the cheap news of the sixteenth century: printed on one side, sold for small money, illustrated with a woodcut so that it worked for buyers who could not read the text beneath. Its subjects were the things that sold — comets, monstrous births, floods, plagues, armies in the sky — and its purpose was very often homiletic. A prodigy was not reported because it was curious. It was reported because it meant something, and the text existed to say what. Sheets of exactly this kind were collected in quantity by the Zurich pastor Johann Jakob Wick, whose compilation is why a good deal of this material survives at all.
So the genre rewarded the spectacular and supplied the interpretation in advance. None of that makes an account false. It does mean the document is not a neutral report of a morning, and was never trying to be.
The two readings
From the middle of the twentieth century the Nuremberg sheet was taken up in UFO literature as a record of craft: spheres and cylinders and discs manoeuvring, described by people with no vocabulary for machines, which is why they reached for crosses and rods and spears.
The competing reading is atmospheric. Ice crystals in high cloud produce sun dogs, parhelia, halos, sun pillars and the intersecting arcs that make a cross of light around the sun — an unusually complete display can put multiple bright discs and crossing beams in the sky at once, close to dawn, which is when this was reported. Colour and apparent motion follow from the sun's movement and from changes in the cloud. Those who take this view point out that the display forms around the sun, and Glaser's text says the shapes came out of the sun.
The halo family is worth setting out, because "sun dog" undersells what a full display can put in the sky. Plate-shaped ice crystals drifting horizontally in cirrus produce bright spots either side of the sun at twenty-two degrees, often coloured, and a rich display can add the 22-degree halo itself, a white parhelic circle running right around the sky at the sun's height, an upper tangent arc, a sun pillar rising vertically, and the crossing of pillar and parhelic circle — a cross of light centred on the sun. Several bright discs, rods and a cross, all at once, low in a cold April dawn, is a specific and well-attested thing for the sky to do.
Two details are usually offered against the atmospheric reading. The account describes shapes moving against one another for over an hour rather than hanging in fixed positions, and it ends with objects falling to earth and producing smoke, which halos do not do. Against that: an hour is about right for a display to evolve and decay as the cloud shifts and the sun climbs, the apparent motion of brightenings within a changing display can read as manoeuvre, and the fall and the smoke arrive at the point in the text where the report turns into its moral.
Neither reading can call on anything beyond the sheet itself. There is no second independent account of that morning in Nuremberg, no instrument record, and no material residue, despite the text describing objects burning as they came down.
What the document can and cannot settle
What the broadsheet establishes is that in April 1561 a number of people in Nuremberg believed they had seen something extraordinary in the sky, and that a printer thought it worth setting in type within weeks. That is a real historical fact about a real morning, and it is not in dispute.
What it cannot establish is what was overhead. The sheet is a single source, written to a religious purpose, in a genre that rewarded the spectacular, by a man who was not himself a claimed witness. Its illustration is a woodcut made to sell a story, not a drawing made at the scene.
The habit of reproducing the image with a modern caption asserting an aerial battle between craft removes the one thing that makes it worth having: it was printed as a portent, and the text says so in its own words. Read as what it is — a piece of sixteenth-century religious news — it remains the best-preserved early record anyone citing historical sightings can point to, which is a smaller claim than the one usually made for it and a considerably more durable one.