Galaxy rotation curve

The rotation curve of a galaxy describes the relationship between its rotational speed and the distance from the galaxy center.

By observing the Doppler shift of spectral lines in the stellar spectra was observed in the 70 years that galaxies not as a rigid body ( rotation curve: origin line, green in the picture) or as a Keplerian system ( faster drop in the rotation curve outward; blue rotate the picture), as would be expected from a system gravitationally bound. In reality, the rotation curves of many galaxies, including the Milky Way remain long constant ( flat rotation curve, red in the picture) - after an increase in the inner regions, corresponding to the rotation of a rigid body ( gray in the figure).

The explanation must be assumed that far more matter present in galaxies, as you can see. This led to the hypothesis of dark matter.

Another explanation is to modify the Newtonian laws, as it is assumed in the modified Newtonian dynamics.

The differential rotation of the Milky Way is described by the Oort rotation formulas.

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