Quote:In some galaxies star forming regions appear blue. In others they appear red. Why is this? I thought star forming regions should all have the same characteristics of glowing hydrogen gas - red./Ira
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Quote:Hi Ira,I think this is why:The clouds are dark while protostars contract within them and glow in the infrared. Maybe some nearby stars excite the cloud enough for some hydrogen glow. Color of cloud is red or dark or perhaps some reflection from nearby stars.The new stars ionize the cloud and make it glow red.The new stars disperse the cloud and the regions change from red to blue in color. The sequence above is perhaps illustrated by M8, M42, Rosette, to M45...
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Quote:The brightest stars in such regions are hot, young O- and B-types, hence the blue color. Emission nebulae--commonly associated with star forming regions--often feature strong peaks in Nitrogen II and Hydrogen-alpha emissions, hence their red appearance in digital images.Bill in Flag
Quote:What had me confused is that the galaxies in these photos were either totally red or totally blue. Since star formation regions even in star burst galaxies must be rich in hydrogen gas which would glow red, how can there be star burst galaxies that are just blue?/ira
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