Types of galaxies (Credit: NASA)
In the late 1970s, astronomers Vera Rubin and Albert Bosma independently found that spiral galaxies rotate at a nearly constant speed: the velocity of stars and gas inside a galaxy does not decrease with radius, as one would expect from Newton’s laws and the distribution of visible matter, but remains approximately constant. Such ‘flat rotation curves’ are generally attributed to invisible, dark matter surrounding galaxies and providing additional gravitational attraction. Now a team led by Case Western Reserve University researchers has found a significant new relationship in spiral and irregular galaxies: the acceleration observed in rotation curves tightly correlates with the gravitational acceleration expected from visible mass only.
“If you measure the...
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