Helium star

Helium star ( eng. Helium star ) is a star of spectral class O or B (blue), which has extremely strong helium lines and weaker than usual hydrogen lines, indicating a strong stellar wind and mass loss from the outer shell. Extreme helium stars have a lack of hydrogen in the spectrum. ^[1] Real helium stars lie near the helium main sequence , similar to the main sequence formed by hydrogen stars. ^[2]

Earlier, a star of spectral class B was called a helium star, but now this name does not apply.

Also a helium star was called a hypothetical star, which can be formed by the merger of two helium white dwarfs with a total mass of at least 0.5 times the mass of the Sun, followed by helium burning; The lifetime of such stars is several hundred million years. In this case, the merging components must be on the same evolutionary stage.

The ability of helium stars to turn into stars of another type has been observed for many years. In 2014, a new V445 Kormi helium exploded along with the subsequent SN2012Z explosion, which led to an exchange of mass between the components. In this case, a helium star was formed, possibly later transformed into a red giant after the loss of the hydrogen envelope. ^[3]