This image from the NASA/ESA Hubble Space Telescope shows a spiral galaxy known as NGC 7331. First observed by prolific galaxy hunter William Herschel in 1784, NGC 7331 is located about 45 million light years away, in the constellation of Pegasus (The Winged Horse). . In front of us partially edge-on, the galaxy shows its beautiful arms that rotate like a whirlpool around its bright central region.
Astronomers took this image using Hubble's Wide Field Camera 3 (WFC3), while observing an extraordinary star explosion (a supernova) that can still be seen faintly as a small red dot near the galaxy's central yellow core. Called SN2014C, it rapidly evolved from a supernova containing very little hydrogen to one rich in hydrogen, in just one year. This rarely observed metamorphosis was luminous at high energies and provides a unique glimpse into the final phases of massive, little-known stars.
NGC 7331 is similar in size, shape and mass to the Milky Way. It also has a comparable star formation rate, hosts a similar number of stars, has a central supermassive black hole and comparable spiral arms. The main difference between our galaxies is that NGC 7331 is a barless spiral galaxy: it lacks a “bar” of stars, gas and dust passing through its core, as we see in the Milky Way. Its central bulge also displays a peculiar and unusual rotation pattern, spinning in the opposite direction to the galactic disk itself.
By studying similar galaxies, we hold a scientific mirror up to our own, allowing us to better understand our galactic environment, which we cannot always observe, and galactic behavior and evolution as a whole.
Image credit: ESA/Hubble and NASA/D. Milisavljevic (Purdue University)
Explanation from: https://www.spacetelescope.org/images/potw1805a/
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