  Transition disks are considered sites of ongoing planet formation, and their
dust and gas distributions could be signposts of embedded planets. The
transition disk around the T Tauri star RY Lup has an inner dust cavity and
displays a strong silicate emission feature. Using high-resolution imaging we
study the disk geometry, including non-axisymmetric features, and its surface
dust grain, to gain a better understanding of the disk evolutionary process.
Moreover, we search for companion candidates, possibly connected to the disk.
We obtained high-contrast and high angular resolution data in the near-infrared
with the VLT/SPHERE extreme adaptive optics instrument whose goal is to study
the planet formation by detecting and characterizing these planets and their
formation environments through direct imaging. We performed polarimetric
imaging of the RY~Lup disk with IRDIS (at 1.6 microns), and obtained intensity
images with the IRDIS dual-band imaging camera simultaneously with the IFS
spectro-imager (0.9-1.3 microns). We resolved for the first time the scattered
light from the nearly edge-on circumstellar disk around RY~Lup, at projected
separations in the 100 \,au range. The shape of the disk and its sharp features
are clearly detectable at wavelengths ranging from 0.9 to 1.6 microns. We show
that the observed morphology can be interpreted as spiral arms in the disk.
This interpretation is supported by in-depth numerical simulations. We also
demonstrate that these features can be produced by one planet interacting with
the disk. We also detect several point sources which are classified as probable
background objects.
