  We present an extensive set of photometric and spectroscopic data for SN
2009jf, a nearby Type Ib supernova, spanning from ~20 days before B-band
maximum to one year after maximum. We show that SN 2009jf is a slow evolving
and energetic stripped-envelope SN and is likely from a massive progenitor
(25-30 solar masses). The large progenitor's mass allows us to explain the
complete hydrogen plus helium stripping without invoking the presence of a
binary companion. The supernova occurred close to a young cluster, in a crowded
environment with ongoing star-formation. The specroscopic similarity with the
He-poor Type Ic SN 2007gr suggests a common progenitor for some supernovae Ib
and Ic. The nebular spectra of SN 2009jf are consistent with an asymmetric
explosion, with an off-center dense core. We also find evidence that He-rich Ib
supernovae have a rise time longer than other stripped-envelope supernovae,
however confirmation of this result and further observations are needed.
