  The launch of JWST has ushered in a new era of high precision infrared
astronomy, allowing us to probe nearby white dwarfs for cold dust, exoplanets,
and tidally heated exomoons. While previous searches for these exoplanets have
successfully ruled out companions as small as 7-10 Jupiter masses, no
instrument prior to JWST has been sensitive to the likely more common
sub-Jovian mass planets around white dwarfs. In this paper, we present the
first multi-band photometry (F560W, F770W, F1500W, F2100W) taken of WD 2149+021
with the Mid-Infrared Instrument (MIRI) on JWST. After a careful search for
both resolved and unresolved planets, we do not identify any compelling
candidates around WD 2149+021. Our analysis indicates that we are sensitive to
companions as small as ~0.34 MJup outwards of 1."263 (28.3 au) and ~0.64 MJup
at the innermost working angle (0."654, 14.7 au) with 5 sigma confidence,
placing significant constraints on any undetected companions around this white
dwarf. The results of these observations emphasize the exciting future of
sub-Jovian planet detection limits by JWST, which can begin to constrain how
often these planets survive their host stars evolution.
