Image credit: Sloan Digital Sky Survey / William Keel, of Arp 198.

Amazing view of galaxies that look like they’re colliding, but aren’t

These cosmic optical illusions are more common than you think.


“I know there is strength in the differences between us. I know there is comfort where we overlap.” -Ani DiFranco

If the Universe were truly infinite, you could look forever in any given direction and eventually run into stars or galaxies.

Image credit: Sloan Digital Sky Survey / William Keel, of NGC 3861.

At 46.1 billion light years in any given direction, with hundreds of billions of galaxies inside, most regions of the sky don’t just have one galaxy, but many.

Image credit: NASA, of galaxies NGC 4567 and NGC 4568.

Sometimes, these galaxies are close together in physical proximity, leading to gravitational interactions, disruptions, and eventually mergers. But sometimes, it’s just a coincidence.

Image credit: Sloan Digital Sky Survey / William Keel, of galaxy SDSS 0910.

When you look out at the sky, what you see as a two-dimensional region is actually a three-dimensional cone.

Image credit: Sloan Digital Sky Survey / William Keel, of galaxy SDSS 0914 and its “companions”.

Sometimes, multiple galaxies at different distances appear to be right atop one another, even overlapping.

Image credit: Sloan Digital Sky Survey / William Keel, of galaxy SDSS 1012.

While interacting galaxies — ones in the same physical location — show increased rates of star formation, these “coincidence” galaxies are all quiet.

Image credit: Sloan Digital Sky Survey / William Keel, of galaxy SDSS 1103.

Researcher William Keel has been involved in identifying and cataloguing these galaxies for a long time, having identified 88 himself.

Image credit: SDSS / Galaxy Zoo / William Keel, from https://www.dropbox.com/s/3kmunbofj0jsp1x/starsmog54.pdf?dl=0.

The Sloan Digital Sky Survey and the citizen science project Galaxy Zoo have teamed up to push the number known past 1,000.

Image credit: SDSS / Galaxy Zoo / William Keel, from https://www.dropbox.com/s/3kmunbofj0jsp1x/starsmog54.pdf?dl=0.

With no disruption, gas stripping, weird shapes or intense starbursts, these galaxies are spectacular for our eyes alone, nothing more.

Image credit: Sloan Digital Sky Survey / William Keel, of galaxies UGC 5769 and UGC 5770.

Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images, video and no more than 200 words.

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