Starship Asterisk*

A new radial acceleration relation found among spiral and irregular galaxies challenges current understanding – and possibly existence – of dark matter

[img3="In spiral galaxies such as NGC 6946, researchers found that a 1-to-1 relationship between the distribution of stars plus gas and the acceleration caused by gravity exists."]http://dailymedia.case.edu/wp-content/u ... gc6946.jpg[/img3][hr][/hr]

In the late 1970s, astronomers Vera Rubin and Albert Bosma independently found that spiral galaxies rotate at a nearly constant speed: the velocity of stars and gas inside a galaxy does not decrease with radius, as one would expect from Newton’s laws and the distribution of visible matter, but remains approximately constant. Such ‘flat rotation curves’ are generally attributed to invisible, dark matter surrounding galaxies and providing additional gravitational attraction.

Now a team led by Case Western Reserve University researchers has found a significant new relationship in spiral and irregular galaxies: the acceleration observed in rotation curves tightly correlates with the gravitational acceleration expected from the visible mass only. ...

The finding is consistent among 153 spiral and irregular galaxies, ranging from giant to dwarf, those with massive central bulges or none at all. It is also consistent among those galaxies comprised of mostly stars or mostly gas. ...

• Physical Review Letters 117:201101 (11 Nov 2016) DOI: 10.1103/PhysRevLett.117.201101
  arXiv.org > astro-ph > arXiv:1609.05917 > 19 Sep 2016

The distribution of normal matter precisely determines gravitational acceleration in all common types of galaxies, a team led by Case Western Reserve University researchers reports.

[img3="The giant elliptical galaxy NGC 4472. Courtesy of David W. Hogg, Michael R. Blanton, and the Sloan Digital Sky Survey Collaboration."]http://dailymedia.case.edu/wp-content/u ... 59x500.jpg[/img3][hr][/hr]

The team has shown this radial acceleration relation exists in nearby high-mass elliptical and low-mass spheroidal galaxies, building on last year’s discovery of this relation in spiral and irregular galaxies. This provides further support that the relation is tantamount to a new natural law, the researchers say.

“This demonstrates that we truly have a universal law for galactic systems,” said Federico Lelli, formerly an astronomy postdoctoral fellow at Case Western Reserve University and currently a fellow at the European Southern Observatory.

“This is similar to the Kepler law for planetary systems, which does not care about the specific properties of the planet. Whether the planet is rocky like Earth or gaseous like Jupiter, the law applies,” said Lelli, who led this investigation.

In this case, the observed acceleration tightly correlates with the gravitational acceleration from the visible mass, no matter the type of galaxy. In other words, if astronomers measure the distribution of normal matter, they know the rotation curve, and vice versa. ...

• Astrophysical Journal 836(2):152 (20 Feb 2017) DOI: 10.3847/1538-4357/836/2/152
  arXiv.org > astro-ph > arXiv:1610.08981 > 27 Oct 2016 (v1), 23 Jan 2017 (v2)

BDanielMayfield wrote:Doesn't this finding undermine or totally eliminate one of the most important supports for dark matter cosmology?