Dark matter exists: Observations disprove alternate explanations

Phys.org ^ | International School of Advanced Studies (SISSA)

[ETL]

Acceleration as a function of radius in NGC 4455, one of the studied galaxies

As fascinating as it is mysterious, dark matter is one of the greatest enigmas of astrophysics and cosmology
It is thought to account for 90 percent of the matter in the universe, but its existence has been demonstrated only indirectly, and has recently been called into question

New research conducted by SISSA removes the recent doubts on the presence of dark matter within galaxies, disproving the empirical relations in support of alternative theories.

The study, published in the Astrophysical Journal, also offers new insights into understanding the nature of dark matter and its relationship with ordinary matter.

From the expansion of the universe to the movement of stars in the galaxies, there are many phenomena that cannot be explained by the presence of baryonic matter alone.

The attractive force generated by matter is insufficient to explain observable gravitational effects. This had led to the theory of the existence of undetectable dark matter, and the idea that galaxies are embedded in its spherical halo.

"Three years ago, a few colleagues at Case Western Reserve University strongly questioned our understanding of the universe and the in-depth work of many researchers, casting doubt on the existence of dark matter in the galaxies," explains Chiara Di Paolo, a doctoral student of astrophysics at SISSA.

"Analyzing the rotation curves of 153 galaxies, principally the 'classical' spiral kind, they obtained an empirical relationship between total gravitational acceleration of the stars (observed) and the component which we would observe in the presence of only ordinary matter in the classical Newtonian theory.

This empirical relationship, which seemed valid in all the galaxies they analyzed and at any galactic radius, motivated the explanation of gravitational acceleration without necessarily calling into question dark matter, but involving, for example, theories of modified gravity such as modified Newtonian dynamics (MOND)."

Di Paolo and her collaborators wanted to verify this relationship, analyzing the rotation curves of galaxies other than the classical spiral kind—72 galaxies with low surface brightness (LSB) and 34 dwarf disc galaxies.

They produced more extended results, finding a relationship, which, besides total gravitational acceleration and its ordinary component, also involves the galactic radius and the morphology of the galaxies.

"We have studied the relationship between total acceleration and its ordinary component in 106 galaxies, obtaining different results from those that had been previously observed," explains Paolo Salucci, professor of astrophysics at SISSA and one of the research authors.

"This not only demonstrates the inexactness of the empirical relationship previously described but removes doubts on the existence of dark matter in the galaxies.

Furthermore, the new relationship found could provide crucial information on the understanding of the nature of this indefinite component."

[dragnet2]

I shot this of M51 or the Whirlpool Galaxy. It 's a series of 26 exposures x50 second each, calibrated stacked, combined and processed into one image. I needed more data though, as it should have been about 150 x1.5 minute exposures, to get more image data. M51 is about 35 million or so light years from earth. I find galaxies quite fascinating and love visiting them.

[Telepathic Intruder]

The relativistic jets that you typically see in illustrations of black holes are coming from outside the event horizon, where the escape velocity is still below the speed of light. It's not exactly known what causes them, but it's generally believed that the maelstrom of incoming matter near the event horizon from the accretion disk becomes so energetic that a lot of it is forced back out again, in the only direction available: along the poles.

The illustrations are typically just close-up simplifications of what we can actually see happening at greater distances:

[ConservativeMind]

I read the Medium link and I’m still not sure I understand what it described.

How does the initial spiral get started and then can never progress to 360 degrees? If it gets started, it seems like it should be able to continue to get longer tails, the further the stars move out, at least, if the stars always keep the same speed.

I must be missing something.

[samtheman]

Thanks, ETL.

Very interesting.

[Lurker]

If “dark matter” existed it’d be all over my lawn.

L

[bennowens]

The dark matter is between their ears!

[Centurion2000]

Dark Matter, an article of FAITH among “scientists” in the “modern” world.