  We present RadioAstron space-based very long baseline interferometry (VLBI)
observations of the nearby radio galaxy 3C84 (NGC1275) at the centre of the
Perseus cluster. The observations were carried out on September 21-22, 2013 and
involved a global array of 24 ground radio telescopes observing at 5 GHz and 22
GHz, together with the Space Radio Telescope (SRT). Furthermore, the Very Long
Baseline Array (VLBA) and the phased Very Large Array (VLA) observed the source
quasi-simultaneously at 15 GHz and 43 GHz. Fringes between the ground array and
the SRT were detected on baseline lengths up to 8.1 times the Earth's diameter,
providing unprecedented resolution for 3C 84 at these wavelengths. We note that
the corresponding fringe spacing is 125 microarcsec at 5 GHz and 27 microarcsec
at 22 GHz. Our space-VLBI images reveal a previously unseen sub-structure
inside the compact 1 pc long jet that was ejected about ten years earlier. In
the 5 GHz image, we detected, for the first time, low-intensity emission from a
cocoon-like structure around the restarted jet. Our results suggest that the
increased power of the young jet is inflating a bubble of hot plasma as it
carves its way through the ambient medium of the central region of the galaxy.
Here, we estimate the minimum energy stored in the mini-cocoon, along with its
pressure, volume, expansion speed, and the ratio of heavy particles to
relativistic electrons, as well as the density of the ambient medium. About
half of the energy delivered by the jet is dumped into the mini-cocoon and the
quasi-spherical shape of the bubble suggests that this energy may be
transferred to a significantly larger volume of the interstellar medium than
what would be accomplished by the well-collimated jet on its own. The pressure
of the hot mini-cocoon also provides a natural explanation for the almost
cylindrical jet profile seen in the 22 GHz RadioAstron image.
