# GALAXY ROTATION CURVES: AN OVERVIEW

## WHAT'S IN HERE?

This website is devoted to a very important concept in astrophysics: Galaxy Rotation Curves. The content in this website is relevant for the first-year student as well as for the professional astrophysicist. You can find here tools and Interfaces to model mass components in galaxies, an historical background of the famous discrepancy, video demonstrations of rotating galaxies, useful discussions and much more. A special section is devoted to a novel approach that deals with the discrepancy. Have any questions or comments? Don't hesitate to contact us.

## THE DISCREPANCY

The 50-years discrepancy in Galaxy Rotation Curves is in actuality a mismatch between the observed rotational velocities in galaxies and our predictions regarding these velocities. It is customary to plot those velocities as a function of the distance from the galactic center, as can be seen in the graph.

In order to develop some intuition, let's take a look ...

## FITTING TOOLS

Modeling rotation curves using analytical components, fitting actual data, tuning parameters manually and more.

## A NEW APPROACH

A new approach... Wait a minute? Didn't dark matter solve this problem already? Indeed, the dark matter paradigm is widely regarded nowadays as the resolution of this problem. Moreover, dark matter is consistent with other observations, especially in the field of cosmology. Nevertheless, various fundamental issues have led some astrophysicists to be uncomfortable with the current paradigm. These astrophysicists feel it's about time to seriously explore alternatives.

In this section you'll find a promising alternative: a simple new approach to handle galaxy rotation curves without modifying gravity. This new approach has fewer free parameters, fewer physical assumptions and best of all: it offers a better fit to the observed data (did someone say NFW??). It's about time to challenge the mainstream paradigm. This is the place to begin.

Velocity is relative. When one states: "I am moving at a rate of 2 meters per second", one actually assumes that there is some reference point, relative to which he is changing the distance. In exactly the same way, when an astronomer states: "this gas cloud is rotating around the galactic center at a rate of 80 Km/sec", she actually means that she has been supplied with a well defined frame of reference, relative to which this value is valid. The observed values in rotation curves are also valid only with respect to some specific frame of reference. The only question is whether this frame is an inertial one. Why is it relevant? Because currently, when fitting rotation curves, astrophysicists take this quality for granted. Modeling a rotation curve (from the corresponding mass distribution) implicitly relies on this assumption.

## CONTACT US

Thanks for your interest in our research. Please get in touch with us if you have any questions or comments regarding our work or publications. We’d love to hear from you.