We present new HST F275W , F475W , and F814W imaging of the region of the Coma cluster around D100 , a spiral galaxy with a remarkably long and narrow ( 60 \times 1.5 kpc ) ram pressure stripped gas tail .
We find blue sources coincident with the H \alpha tail , which we identify as young stars formed in the tail .
We also determine they are likely to be unbound stellar complexes with sizes of \sim 50 - 100 pc , likely to disperse as they age .
From a comparison of the colors and magnitudes of the young stellar complexes with simple stellar population models , we find ages ranging from \sim 1 - 50 Myr , and masses ranging from 10 ^ { 3 } to \sim 10 ^ { 5 } M _ { \odot } .
We find the overall rate and efficiency of star formation are low , \sim 6.0 \times 10 ^ { -3 } M _ { \odot } yr ^ { -1 } and \sim 6 \times 10 ^ { -12 } yr ^ { -1 } respectively .
The total H \alpha flux of the tail would correspond to a SFR 7 times higher , indicating some other mechanism for H \alpha excitation is dominant .
From analysis of colors , we track the progression of outside-in star formation quenching in the main body of D100 , as well as its apparent companion the S0 D99 .
Finally , we observe the dust extinction in the base of the tail has an outer envelope with remarkably smooth and straight edges , and linear filamentary substructure strongly suggestive of magnetic fields .
These features and the small amount of tail broadening strongly suggest gas cooling restricting broadening , and the influence of magnetic fields inhibiting turbulence .