2D view of the second hydrostatic core at 312 years after its formation as a result of the collapse of a 1 M_⊙ cloud core with an initial temperature of 10 K. The four panels show the (a) Mach number, (b) density, (c) temperature, and (d) entropy within the inner 0.5 au of the 3000 au collapsing cloud core. The velocity streamlines in black indicate the material falling on to the second core and the mixing inside the convective second core. The white contour in panel a showing Mach = 1.0 separates the sub- and supersonic regions. The different contour lines in panel b mark the increase in density towards the centre. When displayed in Adobe Acrobat, it is possible to switch to view the properties of the first core at the snapshot of the onset of the second core formation. A movie of the entire collapse is available online at https://keeper.mpdl.mpg.de/f/f04abdeabdf3472fb56d/.