What does this number measure?
A red supergiant heavily obscured by its circumstellar envelope. The disc shown represents its diameter, twice the adopted radius of 1350 nominal solar radii (1 nominal solar radius = 695 700 km). The value is a dated estimate, not an established size record. This reference uses a uniform angular diameter of 7.8 mas and the distance of 1 610 pc reported in 2012. This apparent diameter may combine the photosphere and the envelope: it is not a clearly resolved photospheric measurement. Published radius estimates differ substantially.
Compare the stated dimensions
The comparison uses the number in each fact sheet: altitude, height, diameter, length or distance, depending on the reference. Two values in metres do not necessarily describe the same property.
Source and limitations
Reference obtained using a uniform angular diameter of 7.8 mas and the distance of 1 610 pc reported in 2012. This apparent diameter may combine the photosphere and envelope: it is not a clear-cut photospheric measurement. Published radius estimates differ widely.
NML Cygni: artistic illustration of a stellar photosphere. A shared generic pattern for comparing diameters; neither a photograph nor a reconstruction of this star. The value and its uncertainties are given in the object information.