by Ann » Mon Jan 23, 2023 6:43 am
Let's look at what processing does to an astronomical image, by comparing Mehmet Hakan Özsaraç's version of Arp 274 with the original NASA image!
As you can see, Mehmet Hakan Özsaraç has "shed more light" on the galaxies of Arp 274 than the original NASA image. The galaxies look brighter in Özsaraç's image, and we see more of the faint old population in each galaxy, as well as more details in the centers of the two larger galaxies. So in short, we get a more generous slice of galactic helping, with more cream and perhaps a cherry on top!
But as a Color Commentator, I'm somewhat critical of the pink color of the center of the large spiral in Özsaraç's image. In RGB+Hα pictures of galaxies, like today's APOD, the pink color signals high levels of hydrogen alpha and high levels of star formation. All the little pink dots that follow the spiral arms of the two spirals of Arp 274 are indeed bright pink nebulas whose color is due to hot young stars whose ultraviolet light ionizes the birth clouds of these stars and makes clouds glow pink.
But we don't normally see galaxies with bright pink centers. It happens, of course, like in NGC 4194. But almost all reasonably large and well-behaved spiral galaxies have yellow centers.
So I have some issues with the pink color of the center of the largest galaxy of Arp 274, which suggests the presence of an explosive starforming event that isn't there.
Then again, the galaxies of Arp 274 will merge in the future. So if the center of the largest spiral of Arp 274 looks like the center of NGC 1512 today (or, in the words of
Tom Lehrer, and with a nod to DL MARTIN, as far as the news has come to Harvard), in the future the center of the merger product of these three galaxies may well look like NGC 4194.
Ann
Let's look at what processing does to an astronomical image, by comparing Mehmet Hakan Özsaraç's version of Arp 274 with the original NASA image!
[float=right][img3="The original image by NASA. Credit: NASA, ESA, M. Livio and the Hubble Heritage Team"]https://stsci-opo.org/STScI-01EVVNY32998T28FVHRDTD01SD.jpg[/img3][/float][img3="The Colliding Spiral Galaxies of Arp 274.
Image Credit: NASA, ESA, Hubble; Processing & Copyright: Mehmet Hakan Özsaraç"]https://apod.nasa.gov/apod/image/2301/Arp274_HubbleOzsarac_1080.jpg[/img3]
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As you can see, Mehmet Hakan Özsaraç has "shed more light" on the galaxies of Arp 274 than the original NASA image. The galaxies look brighter in Özsaraç's image, and we see more of the faint old population in each galaxy, as well as more details in the centers of the two larger galaxies. So in short, we get a more generous slice of galactic helping, with more cream and perhaps a cherry on top! 🍰 :D
But as a Color Commentator, I'm somewhat critical of the pink color of the center of the large spiral in Özsaraç's image. In RGB+Hα pictures of galaxies, like today's APOD, the pink color signals high levels of hydrogen alpha and high levels of star formation. All the little pink dots that follow the spiral arms of the two spirals of Arp 274 are indeed bright pink nebulas whose color is due to hot young stars whose ultraviolet light ionizes the birth clouds of these stars and makes clouds glow pink.
But we don't normally see galaxies with bright pink centers. It happens, of course, like in NGC 4194. But almost all reasonably large and well-behaved spiral galaxies have yellow centers.
[float=right][img3="The center of barred spiral galaxy NGC 1512. There is a ring of pink nebulas and blue star clusters surrounding the galactic center. Inside the ring, the stars are old and yellow. A thin dust lane threads its way towards the galactic core. Credit: D. Maoz (Tel-Aviv University/Columbia University), A. J. Barth (Harvard CfA), L. C. Ho (Carnegie Obs.), A. Sternberg (Tel-Aviv University and A. V. Filippenko (UC Berkeley)"]https://upload.wikimedia.org/wikipedia/commons/1/1c/NGC_1512.jpg[/img3][/float][img3="NGC 4194, the Medusa merger. The merger of two galaxies has sent huge amount of gas into the center of merger product, setting off a huge starburst there that explosively throws tendrils of pink-glowing gas out of the center. Credit: ESA/Hubble."]https://upload.wikimedia.org/wikipedia/commons/thumb/d/db/Snakes_and_Stones_NGC_4194.jpg/1024px-Snakes_and_Stones_NGC_4194.jpg[/img3]
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So I have some issues with the pink color of the center of the largest galaxy of Arp 274, which suggests the presence of an explosive starforming event that isn't there.
Then again, the galaxies of Arp 274 will merge in the future. So if the center of the largest spiral of Arp 274 looks like the center of NGC 1512 today (or, in the words of [url=https://www.youtube.com/watch?v=AcS3NOQnsQM]Tom Lehrer[/url], and with a nod to DL MARTIN, as far as the news has come to Harvard), in the future the center of the merger product of these three galaxies may well look like NGC 4194.
Ann