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Stars

Wolf-Rayet Stars

There are stars with very peculiar broad, intense emission lines that cannot be fit readily into the H-R diagram. They were first studied in the 1870's by the French astronomers Wolf and Rayet, hence the name. These stars are blue and very hot (more luminous than the O stars) but with tenuous atmospheric envelopes (similar to the M giants). The modern view traces the
Wolf-Rayet Star Eta Carinae development from the massive blue supergiant star, which is on the verge of blowing apart by the enormous radiation pressure. It occupies a region in the H-R diagram, where the surface temperature is 30,000oK and the luminosity is 106 times that for the Sun. It throws off so much material that the inside of the star generated by nuclear fusion such as helium, carbon, nitrogen and oxygen, become visible. It is designated as WN, WC, or WO stars depending on whether it is enriched in nitrogen, carbon or oxygen (Figure 08-12b). Eventually, the successive nuclear fusions turn the core into iron. Then it will go supernova and collapse to either a neutron star or black hole

Figure 08-12b Wolf-Rayet Star [view large image]

Figure 08-12c Eta Carinae [view large image]

 in a period as short as a week. Eta Carinae is an example of such star on the way to its final destruction (Figure 08-12c).

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