(ORDO NEWS) — Although dark matter is a central part of the standard cosmological model, there are still many mysteries surrounding it.
For example, scientists still have not found direct evidence of its existence in the form of particles.
Therefore, some astronomers prefer alternative models such as Modified Newtonian Dynamics (MoND) or Modified Gravity Model.
Most of the visible matter in a galaxy is concentrated in the middle, so one would expect stars closer to the center to have higher orbital velocities.
However, we observe that all the stars in the galaxy rotate at approximately the same speed. The rotation curve is essentially flat.
The solution to dark matter is that galaxies are surrounded by a halo of invisible matter, but in 1983 Mordechai Milgrom stated that our gravitational model was wrong.
At interstellar distances, the gravitational attraction between stars is essentially Newtonian.
Therefore, instead of modifying the general theory of relativity, Milgrom proposed to change Newton’s universal law of universal gravitation.
He argued that gravity has a small residual attraction regardless of distance.
Of course, this led to the need to modify Einstein’s equations. So MoND has been generalized in various ways such as AQUAL which means “quadratic Lagrangian”.
Both AQUAL and the standard LCDM model can explain the observed rotation curves of the galaxy, but there are some differences.
This is where a recent study comes in. One of the differences between AQUAL and LCDM is the rotation speeds of stars in inner orbit and outer orbit.
For LCDM, both must be determined by the distribution of matter, so the curve must be smooth. AQUAL predicts a tiny break in the curve.
The author of the article examined the high-resolution velocity curves of 152 galaxies observed in the Spitzer Photometry and Accurate Rotation Curves (SPARC) database and found a shift that is consistent with AQUAL.
The findings appear to support MoND rather than the standard cosmological theory.
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