that the star is on the asymptotic giant branch and is generating energy through the nuclear fusion of hydrogen and helium along concentric shells surrounding an inert core of carbon and oxygen. The companion, Sigma Librae B, is of the 16th magnitude and over an arc minute away. References External links Libra (constellation) Librae, Sigma M-type giants Brachium Librae, 20 Semiregular variable stars 073714 133216 5603 Durchmusterung objects