Deliberate exaggeration, which no one takes literally, to emphasize a feeling or a situation.
In Dom Casmurro
An anonymous man or woman who passes on the street corner is enough to make us put Sirius inside Mars
Putting "Sirius inside Mars" is an astronomical exaggeration, impossible to take literally, that measures the size of the havoc a mere passerby can cause in a jealous man.
Chapters CI to CXII: The Marriage, the Sea, and the Son, the narrator