Hubble and small DM clumps

Observations by the Hubble Space Telescope of gravitationally-lensed quasars have been used to detect the smallest clumps of dark matter found thus far.

Whilst it is not the dark matter clumps that are doing the lensing- that is done by a galaxy lying between us and the more-distant quasar- the DM clumps do alter the arrangement of the multiple lensed images of the background quasar.

In each case of the eight galaxies examined in the study, the observed images were compared with what would be expected in the absence of any DM; the difference between these reveals the influence of the DM clumps.

Furthermore, the small masses deduced for the clumps supports the idea of these being cold DM clumps, where “cold” means “slow-moving” and refers to the speeds of the DM particles themselves.

Ground-based telescopes found the lensed quasar/galaxy combinations, whilst Hubble was used to obtain the detailed images used in the study.

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