Deutsches Elektronen-Synchrotron (DESY) | 2019 Apr 15
New technique doubles resolution of angular size measurements
Using the unique capabilities of telescopes specialised on cosmic gamma rays, scientists have measured the smallest apparent size of a star on the night sky to date. The measurements with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) reveal the diameters of a giant star 2674 light-years away and of a sun-like star at a distance of 700 light-years. The study establishes a new method for astronomers to determine the size of stars ...
Almost any star in the sky is too far away to be resolved by even the best optical telescopes. To overcome this limitation, the scientists used an optical phenomenon called diffraction to measure the star’s diameter. This effect illustrates the wave nature of light, and occurs when an object, such as an asteroid from our own solar system, passes in front of a star. ... This is a general optical phenomenon called a diffraction pattern and can be reproduced in any school lab with a laser hitting a sharp edge.
The researchers used the fact that the shape of the pattern can reveal the angular size of the light source. However, different from the school lab, the diffraction pattern of a star occulted by an asteroid is very hard to measure. ... Astronomers have measured the angular size of stars this way that were occulted by the moon. This method works right down to angular diameters of about one milliarcsecond, which is about the apparent size of a two-cent coin atop the Eiffel Tower in Paris as seen from New York. ...
Scientists Use Asteroid to Measure Smallest Star Size to Date
Harvard Smithsonian Center for Astrophysics | 2019 Apr 16
Direct Measurement of Stellar Angular Diameters by the VERITAS Cherenkov Telescopes ~ W. Benbow et al