The Whirlpool Galaxy, also known as M51, is a magnificent face-on spiral galaxy. It is interacting with a smaller companion, NGC 5195, a dwarf galaxy connected to its larger neighbor by a tidal bridge of dust. The bridge is visible in the image silhouetted against the central region of the smaller galaxy.
The pair forms one of the prettiest objects in the sky. Its intricate structure, dynamic interaction with a companion galaxy, and rich detail make it one of my favorites and you may have noticed that I use it as the avatar image at the top of each page of this blog.
Whirlpool Galaxy (M51) (88 min total exposure Aug 23 and 25, 2024)
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The location in the sky of the Whirlpool and its companion is close to the star at the end of the handle of the Big Dipper. Recent estimates of distance to the pair place them between 23 and 31 million light years from the earth.
Thw smaller companion galaxy, NGC 5195, is being pulled in by the gravitational force of the Whirlpool Galaxy, and the two galaxies are engaged in a cosmic dance that has been ongoing for hundreds of millions of years. This interaction has likely enhanced the spiral structure of M51, making its arms more pronounced and leading to bursts of star formation as the gravitational forces trigger the collapse of gas clouds. The tidal forces exerted by the two galaxies on each other are thought to play a significant role in shaping their structures, and by studying this interaction, scientists can gain insights into similar processes that occur in other galaxies.
Observations using the Hubble Space Telescope have actually suggested that NGC 5195 is passing behind the Whirlpool. Notice that the end of the black dust tendril does seem to be in front of the smaller galaxy.
M51 is also home to a supermassive black hole at its center, like most large galaxies. This black hole influences the motion of stars and gas in the galaxy’s core, and its presence is a key factor in understanding the dynamics of the Whirlpool Galaxy.
I shared an earlier picture of the Whirlpool Galaxy that I took over four years ago. You can click here to revisit that post.