The missing dark matter in certain galaxies can be explained by the effects of tidal disruption: the gravity forces of a neighboring massive galaxy, literally tearing the smaller galaxy apart.
Peering into the dark.
Not only is the mysterious substance invisible, but it’s also not all where we thought it was
On a fine scale, the Universe seems lumpier than it should be.
Observations by the NASA/ESA Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope (VLT) in Chile have found that something may be missing from the theories of how dark matter behaves. This missing ingredient may explain why researchers have uncovered an unexpected discrepancy between observations of the dark matter concentrations in a sample of massive galaxy clusters and theoretical computer simulations of how dark matter should be distributed in clusters. The new findings indicate that some small-scale concentrations of dark matter produce lensing effects that are 10 times stronger than expected.
Since the 1980s, researchers have been running experiments in search of particles that make up dark matter, an invisible substance that permeates our galaxy and universe. Coined dark matter because it gives off no light, this substance, which constitutes more than 80 percent of matter in our universe, has been shown repeatedly to influence ordinary matter through its gravity. Scientists know it is out there but do not know what it is.
This stuff would have existed for thousands of years before disappearing.
Just as the sun has planets and the planets have moons, our galaxy has satellite galaxies, and some of those might have smaller satellite galaxies of their own. To wit, the Large Magellanic Cloud (LMC), a relatively large satellite galaxy visible from the Southern Hemisphere, is thought to have brought at least six of its own satellite galaxies with it when it first approached the Milky Way, based on recent measurements from the European Space Agency’s Gaia mission.
The answer to the dark-matter mystery may be under our feet.
Dark matter is the mysterious substance that makes up roughly a quarter of the Universe. There is strong indirect evidence for its existence from measurements of cosmic primordial radiation, anomalies in the radial dependence of galactic rotational curves and gravitational lensing. Despite its apparently pivotal role in the Universe the physical origin of dark matter remains unknown. Scientists suspect that it is made of unseen particles that neither reflect nor absorb light, but are able to exert gravity. Two theoretical physicists at the University of York, UK, have a new candidate: a recently-discovered bosonic particle, the d*(2380) hexaquark.
