Humble observations suggest a discrepancy in dark matter theories

Observations made using the Hubble Space Telescope have helped scientists worldwide solve mysteries and gather data since it was placed in orbit many years ago. Recently, astronomers have used Hubble observations to discover a discrepancy between theoretical models of how dark matter should be distributed in galaxy clusters and observations of dark matter’s grip on galaxy clusters.

It is challenging to study dark matter because it doesn’t emit, absorb, or reflect light. The only way scientists know that it’s present is through its gravitational pull on the visible matter in space. Astronomers can detect dark matter by measuring how its gravity distorts space, an effect called gravitational lensing.

Using Hubble observations, scientists have discovered that dark matter in clusters produces gravitational lensing effects ten times stronger than expected. The evidence for the more potent gravitational lensing effects come from highly detailed observations of several massive galaxy clusters using the Hubble telescope and the European Southern Observatories Very Large Telescope in Chile.

Large galaxy clusters are in the biggest repositories of dark matter in the universe. These clusters are held together largely by the dark matter’s gravity, while the individual cluster galaxies also have dark matter. This means that dark matter is distributed in the clusters in both large and small scales. With the higher-than-expected gravitational lensing effects, scientists say that there is a feature of the real universe they aren’t capturing in current theoretical models.

The researcher says that this could signal a gap in the current understanding of the nature of dark matter and its properties. Gravitational lensing is an interesting phenomenon that distorts distant background objects like a funhouse mirror. The distortions can sometimes produce multiple images of the same distant galaxy. The higher the concentration of dark matter in a cluster, the more dramatic the light bending. The image above shows dozens of multiply imaged, lensed, background galaxies.

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