Star formation occurs in molecular gas .
In previous studies , the structure of the molecular gas has been studied in terms of molecular clouds , but has been overlooked beyond the cloud scale .
We present an observational study of the molecular gas at 49.5 ^ { \circ } < l < 52.5 ^ { \circ } and -5.0 { km s ^ { -1 } } < v _ { lsr } < 17.4 { km s ^ { -1 } } .
The molecular gas is found in the form of a huge ( \gtrsim 500 pc ) filamentary gas wisp .
This has a large physical extent and a velocity dispersion of \sim 5 km s ^ { -1 } .
The eastern part of the filamentary gas wisp is located \sim 130 pc above the Galactic disk ( which corresponds to 1.5–4 e-folding scale-heights ) , and the total mass of the gas wisp is \gtrsim 1 \times 10 ^ { 5 } M _ { \odot } .
It is composed of two molecular clouds and an expanding bubble .
The velocity structure of the gas wisp can be explained as a smooth quiescent component disturbed by the expansion of a bubble .
That the length of the gas wisp exceeds by much the thickness of the molecular disk of the Milky Way is consistent with the cloud-formation scenario in which the gas is cold prior to the formation of molecular clouds .
Star formation in the filamentary gas wisp occurs at the edge of a bubble ( G52L nebula ) , which is consistent with some models of triggered star formation .