Ann wrote:I have actually retired from commenting on pictures in the Recent Submissions threads, but I can't resist a particular picture here. Before I comment on that one, however, let me thank everyone else for their splendid contributions here! It's such a joy to look at your great photos! (Rothko, you were on line when I started to write this... what splendid sunsets (sunrises?) you have photographed!)
But I really want to talk about Stephane Zoll's picture of Outters4, a newly discovered faint OIII-emitting nebula inside relatively bright Ha-emitting nebula Sharpless 129. What a fascinating nebula! Is it a planetary nebula? It looks rather like it, but if so, where is the central star? The nebula is centered on a bright blue star, which is, however, not the kind of star you find inside planetary nebulae. The star, HD 202214, is classified alternatively as B0V, B0IV, B0II and O9. My software suggests a V light luminosity of about 8,000 times that of the Sun. The spectral class and V light luminosity makes HD 202214 too cool and bright to be the central star of a planetary nebula. On the other hand, HD 202214 is clearly a remarkable star in itself. Its temperature and V luminosity appears to be comparable to that of great star Alnitak in Orion's Belt, but since Alnitak appears to be farther along in its evolution than HD 202214, the latter star might become a brighter blue star than Alnitak.
My point is that a hot massive star like HD 202214 might possibly have some sort of outburst or its own, just because it is so massive. Particularly if it is at the end of its main sequence lifetime, which seems likely. But HD 202214 also has a companion. My software seems to contradict itself as to how bright the companion is compared with HD 202214 itself. But if the companion is faint, isn't it possible that the companion is in fact a small hot star which has produced a planetary nebula?
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