Free Astronomy Magazine January-February 2021

JANUARY-FEBRUARY 2021 E mbedded within the cluster MACSJ 1206 are the distorted images of distant background galaxies, seen as arcs and smeared features. These distortions are caused by the dark matter in the cluster, whose gravity bends and magnifies the light from faraway galaxies, an effect called gravitational lensing. This phe- nomenon allows astronomers to study remote galaxies that would otherwise be too faint to see. Astronomers measured the amount of gravitational lensing caused by this cluster to produce a detailed map of the distribution of dark mat- ter in it. Dark matter is the invisible glue that keeps stars bound together inside a galaxy and makes up the bulk of the matter in the Universe. [NASA, ESA, G. Cam- inha (University of Groningen), M. Meneghetti (Observatory of Astrophysics and Space Science of Bologna), P. Natarajan (Yale University), and the CLASH team] Universe that are currently available reproduce well what we can infer from gravitational lensing,” said Massimo Meneghetti of the INAF- Observatory of Astrophysics and Space Science of Bologna in Italy, the study’s lead author. “We have done a lot of testing of the data in this study, and we are sure that this mismatch indicates that some phys- ical ingredient is missing either from the simulations or from our under- standing of the nature of dark mat- ter,” added Meneghetti. “There’s a feature of the real Universe that we are simply not capturing in our cur- rent theoretical models,” added Priyamvada Natarajan of Yale Uni- versity in Connecticut, one of the senior theorists on the team. “This could signal a gap in our current un-