Hertzsprung–Russell diagrams thumb|upright=1.4|alt=A scattering of dots on a black background, most yellow and aligned in a roughly vertical band down the center, with some white dots extending in two arms to the left and a few red dots scattered on the right of the image|H–R diagram for the globular cluster M3. There is a characteristic "knee" in the curve at magnitude 19 where stars begin entering the giant stage of their evolutionary path, the main-sequence turnoff.
Hertzsprung–Russell diagrams thumb|upright=1.4|alt=A scattering of dots on a black background most yellow and aligned in a roughly vertical band down the center, with some white dots extending in two arms to the left and a few red dots scattered on the right of the image|H–R diagram for the globular cluster M3. There is a characteristic "knee" in the curve at magnitude 19 where stars begin entering the giant ,stage of their evolutionary path, the main-sequence turnoff.