Capella Which Actually Consists of Two Stars

Like our sun, Capella is a yellow or golden star. It is the brightest yellow star visible in our sky, much bigger and brighter than our sun in absolute terms, but much farther away, about 42 light-years in contrast to the sun’s 8 light-minutes. Capella actually consists of two stars. Capella A and Capella B, as they’re called, are similar to each other, both roughly 10 times the sun’s diameter. They emit about 80 and 50 times more overall light than the sun, respectively. Another component to this system, a binary of small red stars, orbits about a light-year away. Capella A and B are both yellow giant stars at the end of their normal lifetimes. Each being more than two and a half times more massive than the sun, the two components of Capella likely are also younger. This is because more massive stars have higher internal pressures, which causes them to burn their nuclear fuel faster and to have shorter lifespans. The stars of Capella are in a transitional period from the smaller, hotter stars they once were, to the cooler and larger red giants they must ultimately become in their final phase. However, for now, their surface temperatures are similar to that of the sun, and so they share its spectral type of G. The two stars we see as Capella mark the 6th brightest star in our sky. Astronomers measure the combined magnitude of this system as 0.08.