New measurements of galaxy rotation lean toward modified gravity as an explanation for dark matter - Phys.org

Although acheronian substance is simply a cardinal portion of the modular cosmological model, it's not without its issues. There proceed to beryllium nagging mysteries astir the stuff, not the slightest of which is the information that scientists person recovered nary nonstop particle grounds of it.

Despite galore searches, we person yet to observe dark substance particles. So immoderate astronomers favour an alternative, specified arsenic modified Newtonian dynamics (MoND) oregon modified gravity model. And a caller survey of galactic rotation seems to enactment them.

The thought of MoND was inspired by galactic rotation. Most of the disposable substance successful a postulation is clustered successful the middle, truthful you'd expect that stars person to the halfway would person faster orbital speeds than stars farther away, akin to the planets of our star system. What we observe is that stars successful a postulation each rotate astatine astir the aforesaid speed. The rotation curve is fundamentally level alternatively than dropping off. The acheronian substance solution is that galaxies are surrounded by a halo of invisible matter, but successful 1983 Mordehai Milgrom argued that our gravitational exemplary indispensable beryllium wrong.

At interstellar distances, the gravitational attraction betwixt stars is fundamentally Newtonian. So alternatively than modifying general relativity, Milgrom projected modifying Newton's cosmopolitan instrumentality of gravity. He argued that alternatively than the unit of attraction arsenic a axenic inverse quadrate relation, gravity has a tiny remnant propulsion careless of distance. This remnant is lone astir 10 trillionths of a G, but it's capable to explicate galactic rotation curves.

Of course, conscionable adding a tiny word to Newton's gravity means that you besides person to modify Einstein's equations, arsenic well. So MoND has been generalized successful assorted ways, specified arsenic AQUAL, which stands for "a quadradic Lagrangian." Both AQUAL and the modular LCDM exemplary tin explicate observed galactic rotation curves, but determination are immoderate subtle differences.

This is wherever a caller survey comes in. One quality betwixt AQUAL and LCDM is successful the rotation speeds of interior orbit stars vs. outer orbit stars. For LCDM, some should beryllium governed by the organisation of matter, truthful the curve should beryllium smooth. AQUAL predicts a tiny kink successful the curve owed to the dynamics of the theory. It's excessively tiny to measurement successful a azygous galaxy, but statistically, determination should beryllium a tiny displacement betwixt the interior and outer velocity distributions.

So the writer of this insubstantial looked astatine high-resolution velocity curves of 152 galaxies arsenic observed successful the Spitzer Photometry and Accurate Rotation Curves (SPARC) database. He recovered a displacement successful statement with AQUAL. The information seems to enactment modified gravity implicit modular acheronian substance cosmology.

The effect is exciting, but it doesn't conclusively overturn dark matter. The AQUAL exemplary has its ain issues, specified arsenic its disagreement with observed gravitational lensing by galaxies. But it is simply a triumph for the underdog theory, which has immoderate astronomers cheering "Vive le MoND!"

The probe is published connected the arXiv preprint server.