Betelgeuse is ~47 milliarcseconds in diameter, making it one of the largest stars (in angular diameter terms) observable from Earth. It was first resolved using the Michelson Stellar Interferometer (which had a diameter of 20 meters) in the 1880s.

I don't know the observational wavelength for the images in the article (VLT-SPHERE has filters that go from ~1-2 microns), but if the image were in H-band (1.6 micron wavelength) the resolution of the 8.2 meter telescope is ~49 milliarcsecond, putting this image just at the formal resolution limit. Still, quite impressive stuff.