NGC 1554

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NGC 1554, Struve's Lost Nebula, is a list entry in the New General Catalogue of Nebulae compiled by John L. E. Dreyer. The nebula was discovered by the German-Russian astronomer Otto Wilhelm von Struve and confirmed by Heinrich Louis d'Arrest. [1]

Dreyer describes it as

!!! var, S, R, Nn = *13

which in NGC's encoding is expanded to

a magnificent or otherwise interesting object, variable, small, round, nucleus north of a star of the 13th magnitude
Reported Location of NGC 1554 by Otto Wilhelm von Struve relative to NGC 1555

The identification is uncertain; many sources think it is related to NGC 1555, Hind's Variable Nebula, but at NGC 1554's coordinates, (epoch J2000) 04h 22m 00.0s +19° 36′ 00″ there is no nebula. However, there is a 14th magnitude star, 4' west-southwest of T Tauri. [1] So there's a possibility that the nebula Struve discovered was surrounding a variable star and it only flares up every now and then (perhaps even on a centuries long cycle).