by Ann » Thu Sep 10, 2015 2:12 pm
You are both absolutely right, Nitpicker and Joe Stieber. That is indeed Gamma Musca. And I agree with Joe, there are no seventh-magnitude stars flanking it.
Centaurus and Crux.
Credit: Akira Fuji/ David Malin images
Gamma Musca is a member (and a bit of an outlier) of the Sco-Cen association, the nearest loose scattering of massive blue stars. The distance to Gamma is 325 light-years, almost exactly the same as the distance to one of the grandest members of the Lower Sco-Cen association,
Acrux, the Alpha star of the southern Cross. Fascinatingly though, while the Sco-Cen association is widespread and rich - it clutters up Centaurus and Lupus with blue brilliance and really makes its presence known in Scorpius and Crux - I can only think of a single O-type star (O9.5V) that is a member of that association, and that is the fainter component of binary star
Sigma Scorpii. It seems probable that the Sco-Cen association only ever produced one O-type star that put its B-type brethren far behind it, and that is Antares. Antares is now a red supergiant, of course!
Interestingly, the Orion association seems less rich than Sco-Cen, but its brightest and most massive members outshine and outweigh the brightest and most massive ones in Sco-Cen. But perhaps Orion is every bit as rich in massive blue stars as Sco-Cen, but its members seem far less spread out in the sky, because they are farther away.
Ann
You are both absolutely right, Nitpicker and Joe Stieber. That is indeed Gamma Musca. And I agree with Joe, there are no seventh-magnitude stars flanking it.
[float=left][img2]http://www.mso.anu.edu.au/~murphysj/img/press_scocen.jpg[/img2][c][size=85]Centaurus and Crux.
Credit: Akira Fuji/ David Malin images[/size][/c][/float]Gamma Musca is a member (and a bit of an outlier) of the Sco-Cen association, the nearest loose scattering of massive blue stars. The distance to Gamma is 325 light-years, almost exactly the same as the distance to one of the grandest members of the Lower Sco-Cen association, [url=https://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Acrux_kstars.png/250px-Acrux_kstars.png]Acrux[/url], the Alpha star of the southern Cross. Fascinatingly though, while the Sco-Cen association is widespread and rich - it clutters up Centaurus and Lupus with blue brilliance and really makes its presence known in Scorpius and Crux - I can only think of a single O-type star (O9.5V) that is a member of that association, and that is the fainter component of binary star [url=https://upload.wikimedia.org/wikipedia/it/thumb/e/e3/Sh2-9.jpg/270px-Sh2-9.jpg]Sigma Scorpii[/url]. It seems probable that the Sco-Cen association only ever produced one O-type star that put its B-type brethren far behind it, and that is Antares. Antares is now a red supergiant, of course!
Interestingly, the Orion association seems less rich than Sco-Cen, but its brightest and most massive members outshine and outweigh the brightest and most massive ones in Sco-Cen. But perhaps Orion is every bit as rich in massive blue stars as Sco-Cen, but its members seem far less spread out in the sky, because they are farther away.
Ann