Historically, galactic rotation curves have suggested that galaxies are surrounded by a vast amount of invisible matter, otherwise known as a dark matter halo. A few weeks ago, a team of astrophysicists published a result that completely contradicts these halo models and could even change the popular understanding of dark matter. The team found that galactic rotation curves can be calculated explicitly from a simple equation that only depends on the amount of visible matter in the galaxy. The exact implications of this finding are still unclear, but the authors do suggest a few possibilities.
At first glance, the group’s result suggests one could successfully develop a model of galactic rotation curves by modifying gravity, rather than adding in dark matter. However, astrophysicists have made several other observations of the universe that imply modifying gravity isn’t the best way to successfully describe nature. Alternatively, this result could imply a surprising coupling between regular and dark matter, making the two types of matter more correlated than expected. If this scenario were the case, the next step would be to try and probe this coupling in other dark matter experiments.
There is a great deal of excitement surrounding the announcement. It is rare in science to find such a simple equation, with no adjustable parameters that describe observed data. The finding also appears to apply to all spiral and irregular galaxies, regardless of shape or size. Such an elegant and universal relationship suggests a new discovery could be just around the corner.
Acknowledgements: Many thanks to Emma Tolley, a PhD graduate student in Physics. Emma is a member of the Harvard ATLAS group, and is currently searching for dark matter signatures at the LHC.
Managing Correspondent: Karri DiPetrillo
Rotating Galaxies could prove dark matter wrong – Forbes Science