  We report on analysis using the James Webb Space Telescope (JWST) to identify
a candidate progenitor star of the Type II-plateau supernova SN 2022acko in the
nearby, barred spiral galaxy NGC 1300. To our knowledge, our discovery
represents the first time JWST has been used to localize a progenitor system in
pre-explosion archival Hubble Space Telescope (HST) images. We astrometrically
registered a JWST NIRCam image from 2023 January, in which the SN was
serendipitously captured, to pre-SN HST F160W and F814W images from 2017 and
2004, respectively. An object corresponding precisely to the SN position has
been isolated with reasonable confidence. That object has a spectral energy
distribution (SED) and overall luminosity consistent with a single-star model
having an initial mass possibly somewhat less than the canonical 8 Msun
theoretical threshold for core collapse (although masses as high as 9 Msun for
the star are also possible); however, the star's SED and luminosity are
inconsistent with that of a super-asymptotic giant branch star which might be a
forerunner of an electron-capture SN. The properties of the progenitor alone
imply that SN 2022acko is a relatively normal SN II-P, albeit most likely a
low-luminosity one. The progenitor candidate should be confirmed with follow-up
HST imaging at late times, when the SN has sufficiently faded. This potential
use of JWST opens a new era of identifying SN progenitor candidates at high
spatial resolution.
