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Colliding Galaxies NGC 4038 and NGC 4039 | by Carl Kwadrat
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Colliding Galaxies NGC 4038 and NGC 4039

This is an image of two colliding galaxies: NGC 4038 and NGC 4039. They are located about 45 million light-years from the Earth. The red areas are emission nebulae that contain hydrogen gas and dust. These are sites of star formation in both galaxies. Stellar formation is accelerated in the region where the two galaxies are penetrating each other. Dark interstellar dust lanes and blue-white stellar giants form most of the rest of the galactic images.


The production of this image was the result of a basic experiment to use only two professionally produced black and white science images of the galaxies to form my version of a full color image. The science images are part of the Hubble Legacy Archive (HLA) and are available to the public to produce their own Hubble-based artistic color astrophotos. About a million Hubble Space Telescope (HST) science images, mostly black and white, are available in the HLA for personal use. On their own, the black and white HST science images usually have little aesthetic qualities since they are taken for scientific study and not to produce artistic images. The production of aesthetic full color images is a secondary usage of the HST data that anyone with the patience, digital image processing skills, and knowledge of HLA data mining can undertake.


The image above was formed from two separate black and white science images extracted from the HLA. One black and white image was taken with a blue filter in front of an HST camera sensor and the other was taken with a red filter in front of the sensor. To get the missing black and white pseudo-green filtered image, I averaged the two extracted black and white HLA images using Photoshop (PS) CS5 since green lies between red and blue in the light spectrum. Many entries in the HLA do not contain a set of three black and white images filtered in red, green, and blue and other means must be used to create or supply the missing filtered images in order to build a full color composite image.


Red, green, and blue monochrome images can be blended together in PS to produce a single full color RGB computer screen rendition of the original object that was photographed in black and white by the HST. Variations in the blending process produces subjective artistic differences in the final composite full color image which can provide various aesthetically pleasing representations of the astronomical object.


The three black and white images were colorized into separate red, green, and blue monochrome images in PS. They were used as three separate PS adjustment layers. The three images were manipulated separately using the curves, levels, brightness, contrast, hue, and saturation controls of PS until the desired composite full color appearance was achieved. The blended result of this separate tricolor image manipulation is the single full color composite image shown above in my rendition of NGC 4038 and NGC 4039 using HST data.


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Taken on October 27, 2013