Don’t you love a scientific study that concludes, “after completing this study, we know less … than we did before”? So says Matt Walker of the Harvard-Smithsonian Center for Astrophysics about dark matter.
In the standard cosmological model, most of our universe is made up of stuff we can’t detect. We infer its existence from the effects it has on regular matter (ordinary stuff made of atoms). Astronomers now suspect that there is five times as much of this 'dark matter' as regular matter in the universe.
Dwarf galaxies are particularly good dark matter caches, containing up to 99% dark matter. Current models predict that most of that dark matter should be compressed into the center of those galaxies. However, new measurements conducted by Walker and Jorge Peñarrubia from the University of Cambridge showed that the dark matter was smoothly distributed throughout at least two dwarf galaxies. This is inconsistent with the ideas that dark matter bunches together forming the nuclei of galaxies, and that these clumps attract normal matter.
Clearly, dark matter isn’t what we thought it was. Or should I say, ‘opaquely’?