Sun's Radius

Nominal solar radius

In 2015, the International Astronomical Union passed Resolution B3, which defined a set of nominal conversion constants for stellar and planetary astronomy. Resolution B3 defined the nominal solar radius (symbol ${\displaystyle R_{\odot }^{N}}$) to be equal to exactly695700 km. The nominal value, which is the rounded value, within the 140 km uncertainty band given by Haberreiter, Schmutz & Kosovichev (2008), was adopted to help astronomers avoid confusion when quoting stellar radii in units of the Sun's radius, even when future observations will likely refine the Sun's actual photospheric radius (which is currently only known to about an accuracy of ±100–200 km).