  In recent astronomical observations, an almost dark galaxy, designated as
Nube, has unveiled an intriguing anomaly in its stellar distribution.
Specifically, Nube exhibits an exceptionally low central brightness, with the
2D half-light radius of its stars far exceeding the typical values found in
dwarf galaxies, and even surpassing those observed in ultra-diffuse galaxies
(UDGs). This phenomenon is difficult to explain within the framework of cold
dark matter (CDM). Meanwhile, due to its ultralight particle mass, fuzzy dark
matter (FDM) exhibits a de Broglie wavelength on the order of kiloparsecs under
the typical velocities of galaxies. The interference between different modes of
the FDM wave gives rise to fluctuations in the gravitational field, which can
lead to the dynamical heating of stars within galaxies, resulting in an
expansion of their spatial distribution. In this paper, we aim to interpret the
anomalous stellar distribution observed in Nube as a consequence of the
dynamical heating effect induced by FDM. Our findings suggest that a FDM
particle mass around $1-2\times 10^{-23}$ eV can effectively account for this
anomaly. And we propose that the FDM dynamical heating effect provides a new
insight into understanding the formation of field UDGs.
