▲ Parent and child galaxies entangled by mutual gravity. The spiral galaxy on the left is NGC 5194 (M51a), and the irregular galaxy on the right is NGC 5195 (M51b). / Photo = The Deep Sky Collective – Carl Björk ext. An amazing image of the spiral galaxy Messier 51 (M51), which has never been seen before, was completed through the collaboration of several astrophotographers and was released on August 12 in ‘Astronomical Picture of the Day’ (APOD) operated by the US National Aeronautics and Space Administration (NASA).
A representative colliding galaxy, M51, often referred to as the father-and-son galaxy because it resembles a father and son holding hands, is entry 51 in Charles Messier’s famous catalogue. Seen nearly face-on, the massive galaxy with its swirling spiral structure is also cataloged as NGC 5194 (M51a). Spiral arms and dust lanes sweep in front of companion galaxy NGC 5195 (M51b) (right).
About 31 million light-years distant toward the constellation of the Dog (Canis Hunt), M51 appears faint and blurry in direct telescope viewing. But this strikingly deep image shows in striking clarity the vivid colors of the two galaxies and the extensive tidal disruption created by their mutual gravitational pull.
The final galactic portrait of M51 is a composite of exposures over 10 days (255 hours) by several astrophotographers. The image includes 118 hours of narrowband (narrow wavelengths tailored to purpose and use, unlike the celestial body’s natural electromagnetic waves) data showing the huge cloud of red ionized hydrogen gas found in the M51 system.
Lee Kwang-sik, science columnist joand999@naver.com
