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Space & Astronomy

Older galaxies had a lot less dark matter

By T.K. Randall
March 18, 2017 · Comment icon 10 comments

Why did early galaxies have less dark matter ? Image Credit: NASA/CXC/M. Weiss
Scientists have discovered that dark matter played a much smaller role in galaxies in the early universe.
The study, which was led by astrophysicist Reinhard Genzel from the Max Planck Institute for Extraterrestrial Physics, saw a team of astronomers using the European Southern Observatory's Very Large Telescope in Chile to observe six large star-forming galaxies from the early universe.

Their findings suggested that dark matter was a lot less prevalent in the past than it is today.
Typical galaxies formed during the current era of the universe (such as the Milky Way) have an effective radius (the bright region from which half a galaxy's light is emitted) made up of 50-80% dark matter, whereas the older galaxies appeared to be comprised of as little as 10%.

Exactly why this should be the case remains unclear, however the scientists have suggested that one reason may be due to the fact that these earlier galaxies were subjected to more continuous inflows of normal matter than later galaxies, thus resulting in a lower proportion of dark matter.

These earlier galaxies were also thought to be lot more turbulent than their recent counterparts.

Source: Scientific American | Comments (10)

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Recent comments on this story
Comment icon #1 Posted by Claire. 7 years ago
Comment icon #2 Posted by fred_mc 7 years ago
Interesting. I guess that Erik Verlinde's theory on emergent gravity, which I have found interesting, is wrong then because there would be no reason for dark matter to increase with time with that theory as far as I understand. Dark matter is one of the most fascinating things I know of since it is so ghostlike, invisible and doesn't interact with ordinary matter.
Comment icon #3 Posted by kartikg 7 years ago
can it be that dark matter came from a  different big bang? 
Comment icon #4 Posted by fred_mc 7 years ago
Interesting idea. I think if the extra gravitation we attribute to dark matter would be coming from a parallel universe (perhaps from real matter in a parallel universe), the big bang for that parallel universe would be a separate big bang. I've seen in science documentaries that gravitons can according to string theory possibly pass through the membranes between parallel universes. However, when I google, I can see that scientists have already thought about the idea that the extra gravitation could come from a parallel universe rather than from dark matter in our universe, and discarded that... [More]
Comment icon #5 Posted by kartikg 7 years ago
I am not aware of the gravitational effects diet to parallel universes, my thinking was like big bang within our own universe spewing out dark matter
Comment icon #6 Posted by fred_mc 7 years ago
Hmmm, I don't think it works like that. Big bang gave rise to space-time, which has been expanding since then. I don't think there can be another big bang inside of our universe since space-time is already here, another big bang would in that case give rise to another space-time, which would be another universe, I think. I think you're thinking about an explosion inside of our space-time/universe giving rise to dark matter but big bang is not an explosion inside of space-time but something giving rise to space-time itself, and its expansion.
Comment icon #7 Posted by kartikg 7 years ago
Yes I was thinking just like that explosion within an explosion. 
Comment icon #8 Posted by aquatus1 7 years ago
Is dark matter even a thing?  I was under the impression it was more or less a placeholder for a force we couldn't figure out.
Comment icon #9 Posted by Calibeliever 7 years ago
Or, was it just as prevalent but not as condensed around galaxies yet?
Comment icon #10 Posted by Calibeliever 7 years ago
It has always felt a bit like Newton's Aether to me. 

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