where a main sequence star is located on the h-r diagram depends only on its mass.
where a main sequence star is located on the h-r diagram depends only on its?
mass
stellar evolutionary tracks can be plotted on an h–r diagram. for a particular mass, these trace the position of a star throughout its life, and show a track from the initial main sequence position, along the subgiant branch, to the giant branch. when an h–r diagram is plotted for a group of stars which all have the same age, such as a cluster, the subgiant branch may be visible as a band of stars between the main sequence turnoff point and the red giant branch. the subgiant branch is only visible if the cluster is sufficiently old that stars have evolved away from the main sequence, which requires several billion years. globular clusters such as ω centauri and old open clusters such as m67 are sufficiently old that they show a pronounced subgiant branch in their color–magnitude diagrams. ω centauri actually shows several separate subgiant branches for reasons that are still not fully understood, but appear to represent stellar populations of different ages within the cluster.
subgiant
bullet::::- θ muscae is a naked-eye wolf-rayet star, but the majority of the visible light is produced by an o-class main sequence companion and an ob supergiant





























bullet::::- 9 sagittarii is a spectroscopic binary containing o3.5 and o5-5.5 main sequence stars, making for the brightest star visible within the lagoon nebula





























bullet::::- μ columbae is a naked-eye o9.5 main sequence star





























bullet::::- θ orionis c is the brightest star in the trapezium cluster in the orion nebula, an o6 main sequence star with a fainter spectroscopic companion
o-type main-sequence star