Astrophysics (index)

Horizontal Branch

(a second "giant" stage in the evolution of some main sequence stars)

The Horizontal Branch (HB) is a grouping of stars on the H-R Diagram (HRD) that form a horizontal line on the diagram, leading away from the Red Giant branch. These are stars in the range of .5 to 2.3 solar masses, that have just ceased being Red Giants and begin Helium (He) fusion (Triple Alpha Process) in the core and Hydrogen (H) fusion in a shell around it. Their being of similar height in the diagram is because their Luminosity (L) is similar despite differences in color, which reflects Temperature.

(star type)

Referenced by:
Asymptotic Giant Branch (AGB)