Spiral And Irregular Galaxies’ Acceleration Challenge Dark Matter

Dark matter continues to mystify physicists and astronomers. Observations made on spiral and irregular galaxies' rotation movement only add to the controversy of what role does dark matter exactly play in our universe.

Case Western Reserve University researchers have made an important discovery, in that they have observed the acceleration of spiral and irregular galaxies correlates to the acceleration of their visible mass only, according to Phys Org. This observation is said to be consistent among the 153 galaxies studied.

The 153 galaxies studied ranged in different sizes, from dwarf galaxies to large ones. There are those who have large central bulges or don't have one at all. In all the different types of galaxies, their rotations have been constant and are based only on observable matter.

For Professor David Merritt, Professor of Physics and Astronomy at the Rochester Institute of Technology this observation deals a serious and likely fatal challenge to the theory that galaxies are surrounded by dark matter. He said that the rotation curves observed are determined by normal matter, and dark matter doesn't seem to play a part.

"If you measure the distribution of star light, you know the rotation curve, and vice versa," Stacy McGaugh, chair of the Department of Astronomy at Case Western Reserve University and lead author of the study said.

Study of such spiral galaxies such as NGC 6946 shows that there's a one-to-one relationship between the distribution of stars and the acceleration caused by gravity, notes The Daily Galaxy. This is also taking into account the gases that surround stars. This observation shows that the acceleration of stars in galaxies does not decrease with the galaxy's radius.

Since the 1970s it has been proposed that dark matter might be the explanation to why spiral galaxies rotate at constant speeds. This has been observed by Vera Rubin and Albert Bosma. Now McGaugh, together with co-authors Federico Lelli, astronomy postdoctoral scholar at Case Western Reserve and James M. Schombert, astronomy professor at the University of Oregon say that their observation might be a new natural law.

The team isn't about to make a theoretical interpretation yet at this point, though. McGaugh has said that this might point to the Modified Newtonian Dynamics as proposed by Israeli physicist Moti Milgrom. It could also be in the nature of dark matter such as superfluid dark matter as proposed by Justin Khoury.

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