A modified law of gravity correctly predicted, in advance of the observations, the velocity dispersion -- the average speed of stars within a galaxy relative to each other -- in 10 dwarf satellite galaxies of the Milky Way's giant neighbor Andromeda.

The relatively large velocity dispersions observed in these types of dwarf galaxies is usually attributed to dark matter. Yet predictions made using the alternative hypothesis Modified Newtonian Dynamics (MOND) succeeded in anticipating the observations.

Stacy McGaugh, professor of astronomy at Case Western Reserve, and Mordehai Milgrom, the father of MOND and professor of physics at Weizmann Institute in Israel, report their findings, which have been accepted for publication by the Astrophysical Journal.

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