This is Stephan’s Quintet, a group of five galaxies. It was discovered in 1877 by French astronomer Édouard Stephan. Now a grouping of five galaxies in the sky is obviously pretty cool, but it’s cooler than that. Four of the five galaxies, the ones with the yellowish tint, are not just visually grouped together, they are actually grouped together. These four galaxies are the first compact galaxy group discovered, and they are the most studied compact galaxy group.
This is of course what Stephan’s Quintet looked like 300 odd million years ago. The Earth was a different place then, but it would still have been strangely familiar if one was magically transferred there. The land was covered with trees and vegetation. Lots of ferns and seeding plants, but no grass or flowers. Bugs, insects even. Small lizard-like things, and lots of amphibians. I suppose I should say it would look familiar at a distance, up close the bugs and plants and lizard-like things would be odd. The only thing really familiar looking would be the ferns. And the sharks. Sharks have been with us a long time, when nature hits on a good idea, she sticks with it.
However, I digress. So what is meant by a compact galaxy group, and what is its significance? This is a group of galaxies that is so gravitationally bound with each other that they are basically in the process of combining. These galaxies have had a number of close encounters and partial collisions already. It may not look like much in the picture, but the various loops and swirls of stars resulting from these collisions give astronomers great insight into the structure of galaxies. And what science doesn’t know about the structure of galaxies dwarfs what they do know, so research will continue.
As for unscientific observations, imagine what the night sky must look like from a planet in the midst of these collisions. It would be like the Milky Way on steroids, there would be planets where the night sky was nothing but huge galaxies from horizon to horizon. It would be spectacular, and make our starry skies look drab in comparison. And especially considering some of these stars (and attendant planets) will have been flung into intergalactic space as a result of these collisions. People don’t realize that our view of the heavens is terribly obscured by dust seeing as we are deep inside a galaxy. On the other hand, intelligent species on such planets would eventually be dismayed when they realized that travel to other star systems was going to be next to impossible. They would have a great view, but very likely be isolated forever.
Humans at least have a shot at exploring nearby star systems. And that’s a topic for an upcoming post.
(The above image being a NASA image is being used legally. NASA does not endorse Doug’s Darkworld, and my use of their image in no way is meant to suggest that. Credit and copyright: Hubble Legacy Archive, ESA, NASA; Processing: Al Kelly I don’t think I need to explain why I chose an image of Stephan’s Quintet to illustrate a post about … Stephan’s Quintet. Oh, and even in dense clusters, stars are still very very far apart, so these galactic collisions will involve the actual collisions of very few stars.)