In 274 CE, after his campaign against Palmyra, the emperor Aurelian dedicated a temple to Sol at Rome, endowed it richly, created a college of priests of senatorial rank, the pontifices Solis, and instituted games held every fourth year. The measure is well attested and its date is not in dispute. What it meant is.
One long-standing reading, associated above all with Gaston Halsberghe, treats the cult as an import: a Syrian solar god, taken from Emesa or from the eastern campaign, installed at Rome as a new imperial deity with an eastern character. That reading fits the timing and the plunder, and it made Sol Invictus a foreign novelty of the late empire.
A revision led by Steven Hijmans argues the opposite from the material evidence. Sol was worshipped at Rome continuously from the republic onward, holds a place in the earliest calendars, had a temple by the Circus Maximus, and appears steadily on coins and reliefs across the imperial period. On that account Aurelian elevated and reorganised an old Roman cult rather than importing a new one, and the title invictus, already used of Mithras, of Hercules and of Jupiter, is an epithet rather than a signature of origin.
The atlas records both readings and settles neither. The evidence each side leans on is largely different evidence, literary and later for the first, numismatic and archaeological for the second, which is a large part of why the disagreement has proved so durable.