Main sequence
![A Hertzsprung–Russell diagram plots the actual brightness (or absolute magnitude) of a star against its color index (represented as B−V). The main sequence is visible as a prominent diagonal band that runs from the upper left to the lower right. This plot shows 22,000 stars from the Hipparcos Catalogue together with 1,000 low-luminosity stars (red and white dwarfs) from the Gliese Catalogue of Nearby Stars.](/Images/godic/202501/12/HRDiagram2212.png")
![](/Images/godic/202501/12/HR-diag-no-text-2.svg2212.png")
![This graph shows the logarithm of the relative energy output (ε) for the proton-proton (PP), CNO and triple-α fusion processes at different temperatures. The dashed line shows the combined energy generation of the PP and CNO processes within a star. At the Sun's core temperature, the PP process is more efficient.](/Images/godic/202501/12/Nuclear_energy_generation.svg2212.png")
![This diagram shows a cross-section of a Sun-like star, showing the internal structure.](/Images/godic/202501/12/Solar_internal_structure.svg2212.png")
In astronomy, the main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell. Stars on this band are known as main-sequence stars or "dwarf" stars.