Through the articles he dedicated to the works of Amédée Guillemin, Émile Zola cuts a figure as a witness favourable to the diffusion of astronomical culture as practiced by Camille Flammarion in the second half of the 19th century. The intellectual conquest of the heavens even acquires a strategic role in the Zolian discourse of the everlasting quest for truth in art. Nonetheless, beyond its explicit manifestations, the confrontation of the characters from the Rougon-Macquart with the star-specked infinity suggest a different relationship of the writer to the heavens, the latter becoming a source of anxiety, of loss of mastery for man confronted with the meaninglessness of the immensity of brute space. Thus the astronomical motif, with the gap its presents between a discourse favourable to it and its treatment within the space of the novel, is one of the cracks through which the crisis of the Zolian doxa of the conquest of reality through literature shows itself.