The research that started the debate was published in 2003 in the journal Science by Aaron J. Romanowsky and his colleagues. In that article Romanowsky claimed that he found a surprising fact: dark matter, which is thought to be surrounding galaxies across the universe, is absent from one type of galaxy known as an "elliptical" (or rounded) galaxy. Romanowsky’s research puzzled physicists since, until that time, it was commonly thought that dark matter surrounds every galaxy in the universe and causes the further stars in each galaxy to move much faster then they would have normally.

Avishai Dekel, Professor of Physics at the Hebrew University in Jerusalem, decided to address this cosmological puzzle. Drawing on highly advanced computer simulations he was able to calculate that, contrary to the 2003 paper, the stars in the outskirts of elliptical galaxies do not move slower than those in spiral galaxies. This suggests the existence of dark matter haloes surrounding elliptical galaxies similar to those surrounding spiral galaxies.

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