Dark matter may not be completely dark at all

Dark matter may not be completely dark at all
Galaxy cluster Abell 3827 (Image: ESO)
Galaxy cluster Abell 3827 (Image: ESO)
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Galaxy cluster Abell 3827 (Image: ESO)
Galaxy cluster Abell 3827 (Image: ESO)
The European Southern Observatory's Very Large Telescope (Image: ESO)
The European Southern Observatory's Very Large Telescope (Image: ESO)

New studies by astronomers are slowly throwing some light on dark matter, the invisible and mysterious stuff that scientists believe makes up much of the universe. For the first time, astronomers believe they've observed the interactions of dark matter via a factor other than the force of gravity.

Dark matter's gravitational interactions with the parts of the universe that we can actually see are the only reason that we know it exists at all. Weirdly, it has seemed until now that dark matter has no other known interactions with anything in the universe, including itself. A recent study seemed to back up the notion that bits of dark matter appear to just drift through space, and not even interact with each other.

However, new observations of the simultaneous collision of four galaxies in the galaxy cluster Abell 3827 – using the European Southern Observatory's Very Large Telescope (VLT) in Chile and a technique called "gravitational lensing" – seemed to show a "clump" of dark matter around one of the galaxies, lagging a bit behind that galaxy.

This sort of lollygagging is something that scientists have predicted might be observable during collisions if dark matter were to interact with itself through some force other than gravity, even slightly.

"We used to think that dark matter just sits around, minding its own business, except for its gravitational pull," said Richard Massey at Durham University, lead author of a paper on the study. "But if dark matter were being slowed down during this collision, it could be the first evidence for rich physics in the dark sector – the hidden Universe all around us."

Massey was also part of the study from last month which seemed to show that dark matter interacts very little with itself. The researchers say the new findings do not necessarily conflict with the earlier study, however. That's because the new research looks at the motion of individual galaxies rather than galaxy clusters, along with the fact that collisions between them may have lasted longer, allowing a small frictional force to build up over a time span lasting between "only" 100 million years to about a billion years.

Massey believes that when looked at together, the two studies may actually work to put limits on the behavior of dark matter. "We are finally homing in dark matter from above and below – squeezing our knowledge from two directions," he said. "Dark matter, we’re coming for you."

The research paper was recently published in the journal Monthly Notices of the Royal Astronomical Society.

Source: ESO

Bob Flint
The term dark matter lends a sense of mystery, seems to me that perhaps it is colorless, or just invisible to our eyes and instruments.
Jon Smith
Interesting. I've always thought dark matter should instead be called transparent matter as it really isn't dark just not detectable.
IF the Big Bang was true, I think it happened more like 50+ billion years ago. (Using the current 13.7 billion years requires the imaginary inflation theory to explain.) The development of the heavy elements requires there to be several generations of stars which went nova and later reformed concentrating the heavier elements. If about 20% of each generation of stars was too small to go nova, they would become cold invisible cinders in space. After about seven generations of stars, this 20% conversion to cold cinders and only 80% new stars, means that the greatest bulk of the mass of the universe is now cold invisible NORMAL matter and not some imaginary dark matter. (If only 50% of the matter reformed new stars then it would only take three generations of stars to accomplish.) The gravitational effects of all this cold mass and its distribution likely explains any observations being declared imaginary dark energy. Another fly in the ointment is gravitational lensing and refractive index which can distort what we see. I also have a feeling that much of what we see has also been affected by light pressure and electrical charges over the years. Any data extrapolated back billions of years quickly becomes nearly meaningless without knowing what could have affected its path and what clouds of gas or galaxies it passed through on its way to the present. Too many mathematicians have the mistaken idea that somehow good math purifies bad data.
Joseph Lau
I'm thinking of the possibility that 'dark matter' is a form of matter that exists in other yet undetectable dimension(s) and has influence in our own dimension/universe.
As soon as humans have the technology to detect more dimensions I'm sure this 'dark matter' mystery will be easily explainable.
James P Pratt
I agree with Bob. I think dark matter is other dimensions that don't normally interact with our dimension. Like different radio frequencies, the dimensions pass right through each other.
Ralf Biernacki
@Joseph: I agree with you. This gets me thinking of the old concept of the Kaluza-Klein tower. To put it in a nutshell, the theory goes that there is a 5th dimension, either spacelike (real basis vector) or timelike (imaginary basis vector) that is curled up so that it is cyclic; but successive cycles describe not repeatedly the same (ours) spacetime, but overlying layers, as it were, in a Riemannian manifold. Think of a multi-ply spacetime (the eponymous tower). The overlying layers also have matter, but nothing can pass from one layer to another except, and the Kaluza theory is explicit on this, gravitational interaction. Hence the matter in these layers feels the gravitational pull of our matter, and vice versa; the matter in these other layers is our "dark" matter, that we cannot see or interact with, but that pulls at us gravitationally. Kaluza and Klein had this theory formulated by the 1920's, in the spate of innovation that followed up Einstein's relativity theory. It was later neglected when the physics spotlight passed to quantum mechanics and weak/strong interactions. AFAIK, nobody has explicitly disproved or found fault with K-K ideas.