Messier 95: A Test for MOND?

OTA:……………….CDK17

Camera:………….FLI Proline 16803, 9micron pixels, 0.64 arcsec/pxl

Observatory:…. Rodeo, NM (Bernard Miller's Observatory)



EXPOSURES:

…R…….12 x 900 sec.

…B…....9 x 900

…G…...14 x 900

…L……..22 x 900

…H..….13 x 1800 (binned 2x2 and not of much use)

Total exposure 21.5 hours

Processed by Alex Woronow (2021) using PixInsight, Skylum, Topaz, SWT

Have you heard of MOND? It's an acronym for MOdified Newtonian Dynamics, a variation on Newton's law of gravity. It theorizes that the effects of gravity change from the regime that we experience, traditional Newtonian gravity, to something slightly different as its effective acceleration decreases. MOND was proposed as an alternative to invoking Dark Matter (and Dark Energy) to explain a wide variety of unusual behaviors in our Universe.

"Look, Tom, at the unusual behavior of that galaxy's rotation."

"No problem, Mac, we'll just add a dose of dark matter about here." That explains it."

"And, Tom, how did matter in the early universe clump into galaxies in the first place?"

"Well, Mac, just add some dark matter, created in the Big Bang, and Voile!"

The post hoc miracle of dark matter. The problem is, the proposed dark matter "violates" the Physics principle of particle symmetry and, despite years of searching for the dark-matter particles, it mimics the Scarlet Pimpernel:

"They seek him here, they seek him there

Those Frenchies [like most cosmologists] seek him everywhere.

Is he in heaven, or is he in hell?

That damned elusive Pimpernel."

On the other hand, MOND makes predictions rather than just remediating quandaries. MOND does what Karl Popper demanded of a fundamental scientific theory: predict an observation’s outcome before the observation takes place.

For instance, for "flat" spiral galaxies, the rotation speed becomes uniform after a certain distance from the center. Furthermore, that distance varies significantly from one galaxy to the next. The dark matter cosmology does not predict such behavior. But, post hoc, given where the rotation becomes uniform in each galaxy, one can add just the right amount of dark matter in just the right places to make it happen. In distinct opposition, MOND accurately predicts where constant rotational velocity will happen in every individual spiral galaxy before it is measured, given its mass radial luminosity (a surrogate for mass) distribution.

There have been many other predictions made by MOND, many of which could not even be made by the dark-matter theory, and in test after test, MOND a priori predictions do well. Dark matter adherents make adjustments to cure each new failure in their theory, case by case. Furthermore, in the Einsteinian version of MOND, matter clumps into galaxies without the need to invoke dark matter.

This brings us back to M 95. M 95 may be a participant in a new, clever test of MOND. MOND predicts the bar’s rotation rates in a barred galaxy, and M 95 suits the bill. The prediction is that the bar-rotation rates will differ among barred spiral galaxies. It predicts a priori what the rotation rate's numerical value will be and that bars will have velocities that differ from their immediate surrounding spiral structures. Dark-matter theory predicts no such relationship.

The above is my recollections and interpretations of what I have read and heard about MOND versus Dark Matter. I hope I have not wondered too far from the facts. If you are interested in learning more about MOND, you might start with these Zoom presentations:

1. https://www.youtube.com/watch?v=zvXvB55xnSw

2. https://darkmattercrisis.wordpress.com/author/pkroupa/

3. And others in that series that have been presented but not yet posted.