If there ever was a “phantom of the opera” it was the painter Edgar Degas. The Palais Garnier was his haunt, his “own room” (as he called it), a hothouse in which various species of desire—ambitions poetic and prosaic, artistic and erotic—were forever captured by his eye and hand. “Degas at the Opéra” is the first exhibition to examine his intense relationship with the world of tutus and tails. —L.J.