  IC 3418 is a dwarf irregular galaxy falling into the Virgo cluster, and a 17
kpc long trail is seen behind the galaxy, which is considered to have formed
due to ram pressure stripping. The trail contains compact knots and diffuse
blobs of ultraviolet and blue optical emission and, thus, it is a clear site of
recent star formation but in an unusual environment, surrounded by a million
degree intra-cluster medium. We report on our optical spectroscopy of a compact
source in the trail, SDSS J122952.66+112227.8, and show that the optical
spectrum is dominated by emission from a massive blue supergiant star. If
confirmed, our report would mark the farthest star with spectroscopic
observation. We interpret that a massive O-type star formed in situ in the
trail has evolved recently out of the main sequence into this blue supergiant
phase, and now lacks any detectable spectral sign of its associated HII region.
We argue that turbulence within the ram pressure striped gaseous trail may play
a dominant role for the star formation within such trails.
