  This paper reports the first full-Sun vacuum ultraviolet (VUV) emission line
profile originating from the transition region from the chromosphere to the
corona. It is based on a raster scan of the whole solar disk using SUMER/SOHO.
The full-Sun spectrum has a spectral resolution which allows an investigation
of details in the line profile as well as a thorough comparison to stellar
spectra as obtained, e.g. with FUSE or STIS/HST. The full-Sun spectrum shows
enhanced emission in the wings, and is well described by a double Gaussian fit
with a narrow and a broad component. It is shown that the broad component is
due to structures on the solar surface, especially those related to the
magnetic chromospheric network. Thus it is proposed that the broad components
of other solar-like stars are also a consequence of the mixture of surface
structures, and not necessarily a signature of small-scale heating processes
like explosive events, as it is commonly argued. A comparison to spectra of
luminous cool stars shows that the line asymmetries of these stars might also
be a surface structure effect and not or only partly due to opacity effects in
their cool dense winds. These comparisons show the potential of high quality
full-Sun VUV spectra and their value for the study of solar-stellar
connections. As an example, this study proposes that alpha Cen A has a
considerably higher amount of magnetic flux concentrated in the chromospheric
magnetic network than the Sun.
