Abstract: A large fraction of spiral galaxies show filamentary or diffuse star formation well beyond their optical disks, in regions where the disk surface density lies below the threshold for star formation. Cold gas accretion onto the outer disks is thought to drive this star formation. The nature of star formation in such adverse environments where the dark matter halo dominates the mass content, is not well understood. In this talk I will first present some preliminary UV observations of extended disk star formation done with the Ultraviolet Imaging Telescope (UVIT) in two galaxies. Using observations and modelling of another galaxy NGC4701, I discuss how the disk dark matter also plays a role in supporting the extended disk star formation in galaxies. We also briefly describe how this phenomenon can be used to trace dark matter in our low redshift Universe.