In a recently published letter to Nature, we report the discovery of the most X-ray luminous galaxy cluster in the known Universe, within which the intracluster medium is cooling at an unprecedented rate. In the core of this cluster, the brightest cluster galaxy is forming stars at an unmatched rate of 740 Msun/yr, which is highly unusual for this class of galaxy which are typically referred to as "red and dead". We suspect that the extreme cooling and star formation rates are intimately linked: the cooling intracluster gas is most likely providing fuel for the starburst. We request 2 orbits of near-UV and optical broadband WFC3-UVIS imaging in order to morphologically classify this starburst as a result of i) cooling, infalling gas (filamentary UV emission); ii) a recent merger (tidal tails with both UV and optical emission); or iii) a starburst- or AGN-driven wind (wide opening angle). These data will also allow us to determine the stellar populations of both the starburst and the underlying, older stellar populations, and will provide a much sharper view of the central AGN, allowing us to more carefully extract the contribution to the extended UV emission from young stars. Our early results have already received substantial attention from the international press, and we expect that a dramatically improved picture of the heart of this cluster would stir up as much, if not more, interest from the public. Straightforward broad-band imaging in 2x near-UV filters (F225W, F336W) and 3x optical filters (F475W, F625W, F814W). We use a 2-pt dither pattern, since our exposures are <1000s and we are concerned with maximizing S/N. Since our target is relatively small, we opt to use a single quadrant (80"x80") in order to reduce read-out time. UNRESOLVED STELLAR POPULATIONS AND GALAXY STRUCTURE 0 false 0.0 0.0 false false false false SUPPORTED GALAXY COOLING FLOW ELLIPTICAL EMISSION LINE NEBULA SEYFERT STARBURST J2000 WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F775W WFC3/UVIS Imaging No No F814W POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 1 false The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13102 :visit-id "01" :proposal-version -1 :trans-version "20120802" :date "17-Aug-2012 14:58:57.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 281552 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13102 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13102 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2997 :al-overhead-at-end 165 :internal-dur-at-end 344 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3333 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 13102 :visit-id "02" :proposal-version -1 :trans-version "20120802" :date "17-Aug-2012 14:58:59.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 422320 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 13102 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 13102 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 3000 :al-overhead-at-end 165 :internal-dur-at-end 498 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3333 :pcs-gap 0 ) false 1 0