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Context. Small-scale bright features in the photosphere of the Sun, such asfaculae or G-band bright points, appear in connection with small-scale magneticflux concentrations.  Aims. Here we report on a new class of photospheric bright points that arefree of magnetic fields. So far, these are visible in numerical simulationsonly. We explore conditions required for their observational detection.  Methods. Numerical radiation (magneto-)hydrodynamic simulations of thenear-surface layers of the Sun were carried out. The magnetic field-freesimulations show tiny bright points, reminiscent of magnetic bright points,only smaller. A simple toy model for these non-magnetic bright points (nMBPs)was established that serves as a base for the development of an algorithm fortheir automatic detection. Basic physical properties of 357 detected nMBPs wereextracted and statistically evaluated. We produced synthetic intensity mapsthat mimic observations with various solar telescopes to obtain hints on theirdetectability.  Results. The nMBPs of the simulations show a mean bolometric intensitycontrast with respect to their intergranular surroundings of approximately 20%,a size of 60-80 km, and the isosurface of optical depth unity is at theirlocation depressed by 80-100 km. They are caused by swirling downdrafts thatprovide, by means of the centripetal force, the necessary pressure gradient forthe formation of a funnel of reduced mass density that reaches from thesubsurface layers into the photosphere. Similar, frequently occurring funnelsthat do not reach into the photosphere, do not produce bright points.  Conclusions. Non-magnetic bright points are the observable manifestation ofvertically extending vortices (vortex tubes) in the photosphere. The resolvingpower of 4-m-class telescopes, such as the DKIST, is needed for an unambiguousdetection of them.

Non-magnetic photospheric bright points in 3D simulations of the solar atmosphere