Definitions for "Horizontal branch"
A sequence of stars in the H-R diagram of a globular cluster, extending horizontally across the diagram to the left from the red-giant region. These are probably stars undergoing helium burning in their cores, by the triple-alpha reaction.
band of stars running horizontally at M ~ 0.6 in the HR diagrams of old, low-heavy-element stellar clusters: these are low mass stars burning helium in their cores.
In the H-R diagram of a globular cluster, the sequence of stars extending from the red giants toward the blue side of the diagram; includes RR Lyrae stars.
Keywords:  plumbing, stack, drain, fixtures, pipes
Lateral drain pipes that run from plumbing fixtures to the waste stack in a building or in the soil.
Lateral drain pipes which run from the plumbing fixtures to the waste stack in a building or into the soil.