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Why do spiral galaxies appear blue

by khristine


Why do spiral galaxies appear blue

Astronomy defines a galaxy as any huge gathering of stars, gas and dusts, dark matter”, nebulae, and other known astronomical entities that exists in the universe. As numerous as the stars in the sky, there are also billions of galaxies that are present up in that one big universe, some are small containing only million of stars while others can be as big as billions of stars combined.

There are three different types of galaxies at hand, and they are often distinguished by its shape that is either elliptical, spiral, or irregular in formations. As a general rule, the shape of the galaxy is also defined by its color wherein elliptical galaxies appear to be red while spiral galaxies appear to be blue.

The difference in color between galaxies is primarily due to the kinds of stars that constitutes it. Galaxies that are mostly composed of older stars and has less energy appear to be red in color. Galaxies that are composed of mostly younger stars, overflowing with energy and are hotter too, are blue in color.

Other factors that are viewed to affect the color of galaxies are due to the presence of dusts and metallic elements in it. It has been known that different dust particles tend to block the blue light which emanates from the stars thus impressing a darker red color than its original shade.

Also, the presence of metallic elements” (elements that is neither made up of helium metals or hydrogen) can create a reddish hue, thus stars that have low presence of metals may appear to be bluer in the sky.

Another fascinating color effect may depend on the movement of galaxies. Galaxies that is moving away from the Earth looks redder, known as the red shift” effect.  Conversely, galaxies that are closer or moving nearer appear to be bluer.

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