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Could Photon Mass Contribute to the Rotational Dynamics of Galaxies and Negate the Need for Dark Matter?

Posted by Guy Pirro   03/18/2019 06:45PM

Could Photon Mass Contribute to the Rotational Dynamics of Galaxies and Negate the Need for Dark Matter?

Dark Energy, Dark Matter, Dark Science. The outer parts of every single spiral galaxy that astronomers look at are traveling so fast that they should be flying apart. By fitting a theoretical model of the composition of the universe to the combined set of cosmological observations, astrophysicists have come up with a composition for the Universe that is approximately 68 percent dark energy, 27 percent dark matter, and just 5 percent normal matter.

But what is dark matter? We are much more certain about what dark matter is not than we are about what it is. First, it is dark, meaning that it is not in the form of stars and planets that we see. Observations show that there is far too little visible matter in the universe to make up the 27 percent required by the observations. Second, it is not in the form of dark clouds of normal matter, matter made up of particles called baryons. We know this because we would be able to detect baryonic clouds by their absorption of radiation passing through them. Third, dark matter is not antimatter, because we do not see the unique gamma rays that are produced when antimatter annihilates “normal” matter. Finally, we can rule out large galaxy-sized black holes on the basis of how many gravitational lenses we see. High concentrations of matter bend light passing near them from objects further away, but we do not see enough gravitational lensing events to suggest that such objects to make up the required 27 percent dark matter contribution.

However, at this point, there are still a few dark matter possibilities that are viable. Baryonic matter could still make up the dark matter if it is all tied up in brown dwarfs or in small, dense chunks of heavy elements that we simply cannot see. These possibilities are known as massive compact halo objects, or "MACHOs." But the most common view is that dark matter is not baryonic at all, but that it is made up of other, more exotic particles like axions or WIMPS (Weakly Interacting Massive Particles). However, physicists in Germany are now hypothesizing that the mass of photons (which are particles of light) could possibly be responsible for the observed rotational dynamics of spiral galaxies. (Image Credit: NASA, ESA, Hubble)

 


 

Could Photon Mass Contribute to the Rotational Dynamics of Galaxies and Negate the Need for Dark Matter?

The rotation of stars in galaxies like our Milky Way is puzzling. The orbital speeds of stars should decrease with their distance from the center of the galaxy, but in fact stars in the middle and outer regions of galaxies have the same rotational speed. This may be due to the gravitational effect of matter that we can't see. Although researchers have been seeking it for decades now, the existence of this imaginary construct referred to as “Dark Matter” has yet to be definitively proven -- We still don't know what it is made of or even if it exists at all. With this in mind, physicists Dmitri Ryutov, Dmitry Budker, and Victor Flambaum have suggested that the rotational dynamics of galaxies might be explained by other factors. They hypothesize that the mass of photons, which are particles of light, might be responsible.

Professor Dmitri Ryutov, who recently retired from the Lawrence Livermore National Laboratory in California, is an expert in plasma physics. He was awarded the American Physical Society's (APS) 2017 Maxwell Prize for Plasma Physics for his achievements in the field. Physicists generally credit Ryutov with establishing the upper limit for the mass of the photon. As this mass, even if it is nonzero, is extremely small, it is usually ignored when analyzing atomic and nuclear processes. But even a vanishingly tiny mass of the photon could, according to the scientists' collaborative proposal, have an effect on large-scale astrophysical phenomena.

While visiting Johannes Gutenberg University Mainz (JGU) in Germany, Ryutov, his host Professor Dmitry Budker of the Helmholtz Institute Mainz (HIM - also in Germany), and Professor Victor Flambaum, Fellow of the Gutenberg Research College of Johannes Gutenberg University Mainz, decided to take a closer look at the idea. They were interested in how the infinitesimally small mass of the photon could have an effect on massive galaxies. The mechanism at the core of the physicists' assumption is a consequence of what is known as Maxwell-Proca equations. These would allow additional centripetal forces to be generated as a result of the electromagnetic stresses in a galaxy.

Are the effects as strong as those exerted by Dark Matter?

"The hypothetical effect we are investigating is not the result of increased gravity," explained Dmitry Budker. This effect may occur concurrently with the assumed influence of dark matter. It may even – under certain circumstances – completely eliminate the need to evoke dark matter as a factor when it comes to explaining rotation curves. Rotation curves express the relationship between the orbital speeds of stars in a galaxy and their radial distance from the galaxy's center.”

 

Dmitry Budker continued, "By assuming a certain photon mass, much smaller than the current upper limit, we can show that this mass would be sufficient to generate additional forces in a galaxy and that these forces would be roughly large enough to explain the rotation curves," said Budker. "This conclusion is extremely exciting."

The physicists even ventured a step further. They looked into how protostars form and discovered that their hypothesis has other implications. It predicts that long-lived, relatively lightweight stars, such as our sun, would have highly elliptical orbits. "Actual observations clearly don't agree with this prediction, meaning our theory can't explain everything." Proca-force effects can thus only be responsible for some of the anomalies in the rotation curves. "We don’t currently consider photon mass to be the solution to the rotation-curve problem. But it could be part of the solution," concluded Budker. "However, we need to keep an open mind as long as we do not actually know what dark matter is."

 

 

For more information:

https://www.hi-mainz.de/news-events/detail/news/him-guests-analyze-the-rotational-dynamics-of-galaxies-and-the-influence-of-the-mass-of-the-photon/

https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy

https://astromart.com/news/show/does-modified-newtonian-dynamics-negate-the-need-for-dark-matter

https://astromart.com/news/show/is-the-universe-hiding-its-missing-mass-in-the-warm-hot-intergalactic-medium

 

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