Darkish matter might be even stranger than we thought, in line with Hubble

A new study with the Hubble Space Telescope suggests that we understand dark matter even less than previously thought. The hypothetical matter is believed to exist based on the mass of the galaxies, but has never been directly observed. New research suggests that our predictions about how dark matter affects spacetime may be far off.

Hubble researchers used a technique called gravitational lenses that observes distant objects by examining how light is bent by gravity of closer objects, with the closer objects acting like a magnifying glass. This enabled them to spot areas that are likely to contain dark matter, which affects the distortion of spacetime, even if it is not directly visible.

The result, which surprised the researchers, was that even small amounts of dark matter in clusters produced a gravitational lensing effect that was ten times stronger than expected.

This suggests that something is missing in our understanding of dark matter. "There is a feature of the real universe that we just don't capture in our current theoretical models," Yale University team members Priyamvada Natarajan said in a statement. "This could signal a gap in our current understanding of the nature of dark matter and its properties, as these exquisite data have enabled us to study the detailed distribution of dark matter on the smallest scales."

This NASA / ESA Hubble Space Telescope image shows the massive MACSJ 1206 galaxy cluster. Embedded in the clusters are distorted images of distant background galaxies that are viewed as arcs and smeared features. Small concentrations of dark matter (shown in the blue impression of this artist) lie over the picture. NASA, ESA, G. Caminha (University of Groningen), M. Meneghetti (Observatory for Astrophysics and Space Research in Bologna), P. Natarajan (University of Yale), the CLASH team and M. Kornmesser (ESA / Hubble)

In the artist's rendering of the MACSJ 1206 cluster, you see distorted galaxies in the background that appear as smears. With the larger smears, distortions due to the gravity lens of the clusters are expected, but there are also minor distortions near the cluster center that the researchers believe are due to the presence of dark matter. This data was used to infer the likely location of clumps of dark matter added in blue by an artist.

Using a combination of the Hubble and the Very Large Telescope, astronomers were able to identify galaxies and estimate their mass, which indicates how much dark matter each galaxy is likely to contain.

"Galaxy clusters are ideal laboratories to study whether the currently available numerical simulations of the universe reproduce well what we can deduce from gravitational lenses," lead author Massimo Meneghetti of the INAF Observatory for Astrophysics and Space Research in Bologna, Italy said in the statement .

This means that more work is needed to really understand what dark matter is and how it interacts with galaxy clusters. "We have performed many tests on the data in this study, and we are certain that this mismatch indicates that some physical component is missing either in the simulations or in our understanding of the nature of dark matter," Meneghetti said.

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