Weirdly Shaped Galaxies Are More Common Than We Thought

Thursday, 01 February 2018 - 6:43PM
Thursday, 01 February 2018 - 6:43PM
Weirdly Shaped Galaxies Are More Common Than We Thought
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New research on the shape and behavior of large galaxies has been published which may upend everything we think we know about the structure of galaxies.

For years, scientists have been perplexed by the shape of our home galaxy, the Milky Way. We live in a large, sprawling galaxy which, according to all conventional wisdom, should be a mess of chaotic celestial debris, with tiny bubbles of outlying dwarf galaxies swirling around at random on the furthest fringe space beyond our main bulk of stars.

Instead, the Milky Way is surprisingly organized, with all of these tiny satellite galaxies falling uniformly into place in a way that defies our understanding of the gravitational pull of dark matter. We'd long since assumed that our galaxy was a rare exception to the standard rule, and that across all of the universe we were one of only a few such weirdly neat and tidy galaxies.

As it turns out, this phenomenon isn't as uncommon as we thought. Not only is our nearest neighbor, the Andromeda galaxy, also a bit of a neat freak, but scientists have also spotted another distant galaxy, Centaurus A, which is similarly organized like clockwork.

According to Federico Lelli, one of the authors of the new study:

Opening quote
"We do not know how these satellite planes form but we do know that they should be rare in the standard cosmological model based on dark matter. However, the three best studied galaxies in the universe-Milky Way, Andromeda and Centaurus A-all show co-rotating planes of satellites."
Closing quote

So apparently, what we once thought was an unusual system of uniformly spaced swirling dwarf galaxies is found on the edges of all three of the galaxies that we've studied the closest. It's looking more like this is the standard shape of a galaxy, rather than the exception to the rule.

This proves a problem for astrophysics as we know it. Our previous assumptions about the chaotic outer layer of most galaxies came from our current understanding of dark matter. Essentially, it's looking an awful lot like we're missing something big about the universe works.

recent computer simulation of the entire universe has proven useful in making some predictions about how stars form, but now, it looks like our existing models have a big hole in their logic. As we used simulations in order to come up with the chaotic dwarf galaxy view of the universe, there's no telling what other elements of our simulations might not actually match up with reality.

The good news is that where there is confusion or where theories are proven wrong, there is an opportunity to learn new stuff. We're going to need to figure out exactly why galaxies don't appear to be behaving the way that we expect them to, and that will mean some fun blue-skies thinking as we attempt to piece together the logic of the universe based on new information that contradicts everything we thought we knew.

Learning all the secrets of the laws of physics is a slow and complicated process, so while we don't get it right every time, it's not really a big deal.

Besides, dreaming up new ideas bit by bit as we figure things out is the most fun part of space exploration.
Science News