Now, observations of several massive galaxy clusters by NASA's Hubble Space Telescope and the European Southern Observatory's Very Large Telescope (VLT) in Chile have revealed a missing mysterious ingredient to current presiding dark matter theories. Astronomers have discovered that small-scale concentrations of dark matter in clusters produce measurements of how gravity distorts space, also called gravitational lensing effects, that are 10 times stronger than previously expected.

"Galaxy clusters are ideal laboratories to understand if computer simulations of the universe reliably reproduce what we can infer about dark matter and its interplay with the luminous matter," said Massimo Meneghetti of the National Institute for Astrophysics (INAF) Observatory of Astrophysics and Space Science of Bologna in Italy, the study's lead author.

"We have done a lot of careful testing in comparing the simulations and data in this study, and our finding of the mismatch persists," Meneghetti continued.