by Ann » Tue Jan 25, 2011 3:42 am
Chris Schur, thank you very much for your fascinating image and your detailed description of M33!
As a former Color Commentator and very much still a color freak, I must, however, comment on what you said here:
Its fairly neutral in color overall, with a B-V index of .55, which makes it somewhat "tawny".
The integrated color of a galaxy is never saturated one way or another. Classic "red" galaxies typically have a color index around +1.0, similar to K0 star Pollux in color, which is not very red at all. It is admittedly redder in color than the Sun.
The three brightly colored "stars" in a row are, from left to right, Mars, Pollux and Castor. The overall color balance is too blue, but the picture makes it obvious, nevertheless, that Pollux is not a brightly red star.
As for "blue" galaxies, their integrated color is never bluer than that of an F star. The bluest spiral galaxy I can think of off hand is NGC 3310, whose color index is +0.33. That makes the galaxy bluer than bright "Winter Triangle star" Procyon, but redder than the second brightest star in the sky, Canopus. And yet, NGC 3310 is one of the bluest galaxies known.
My point is that galaxies are all fairly "neutral" in color. However, as galaxies go, M33 definitely falls into the "blue" category!
Ann
Chris Schur, thank you very much for your fascinating image and your detailed description of M33! :D :D :D
As a former Color Commentator and very much still a color freak, I must, however, comment on what you said here:
[quote]Its fairly neutral in color overall, with a B-V index of .55, which makes it somewhat "tawny". [/quote]
The integrated color of a galaxy is never saturated one way or another. Classic "red" galaxies typically have a color index around +1.0, similar to K0 star Pollux in color, which is not very red at all. It is admittedly redder in color than the Sun.
[img2]http://images.astronet.ru/pubd/2008/05/12/0001227734/Triplets_zubenel_c800.jpg[/img2]
The three brightly colored "stars" in a row are, from left to right, Mars, Pollux and Castor. The overall color balance is too blue, but the picture makes it obvious, nevertheless, that Pollux is not a brightly red star.
As for "blue" galaxies, their integrated color is never bluer than that of an F star. The bluest spiral galaxy I can think of off hand is NGC 3310, whose color index is +0.33. That makes the galaxy bluer than bright "Winter Triangle star" Procyon, but redder than the second brightest star in the sky, Canopus. And yet, NGC 3310 is one of the bluest galaxies known.
My point is that galaxies are all fairly "neutral" in color. However, as galaxies go, M33 definitely falls into the "blue" category!
Ann