Eight gravitationally lensed quasars were used to indirectly detect the smallest clumps of dark matter yet found. Image: NASA, ESA, A. Nierenberg (JPL) and T. Treu (UCLA)
Using the Hubble Space Telescope – and gravitationally lensed quasars – astronomers have found that dark matter can form in much smaller clumps than the galaxy-spanning clouds previously detected, providing strong evidence for the widely accepted “cold dark matter” theory.
Dark matter can be detected indirectly by measuring how its combined gravity affects the motions of stars and galaxies. “Cold” in this case means slow moving. The gravity generated by vast clouds of cold, weakly interacting dark matter particles is thought to provide the glue that keeps galaxies and galaxy clusters from flying apart.
Until now, dark matter concentrations have only been detected in and around medium- to large-size galaxies, prompting theorists to propose theories that include “warm” dark matter, particles that move too fast to merge and form small concentrations. The Hubble observations are consistent with cold dark matter scenarios.
“Dark matter is colder than we knew at smaller scales,” said Anna Nierenberg of NASA’s Jet Propulsion Laboratory in Pasadena, California, leader of the Hubble survey. “Astronomers have carried out other observational ...