VLTI observations of the radii of four small stars

The radii and masses of the four very-low-mass stars now observed with the VLTI, GJ 205, GJ 887, GJ 191 (also known as "Kapteyn''s star") and Proxima Centauri (red filled circles; with error bars). For comparison, planet Jupiter's mass and radius are also plotted (blue triangle). The two curves represent theoretical models for stars of two different ages (400 million years - red dashed curve; 5 billion years - black fully drawn curve; models by Gilles Charier and collaborators at the Ecole Normale Supérieur de Lyon, France). As can be seen, theory and observations fit very well.