Largest ever dark matter map revealed

12 January 2012 by Anonymous (not verified)

Dark matter: we don't know what it is, but we can figure out where it has to be. This week an international team of astronomers, including Oxford Astrophysics' Malin Velander and Lance Miller, showed the world the largest dark matter map ever created. It's caused quite a stir in the world of science; the map has exciting implications for our understanding of the fundamental building blocks of our Universe.

What is dark matter? The simple answer is that nobody knows. What we do know is that only 17 percent of all the matter in the Universe is made of atoms - hydrogen, helium, and other elements. This means that all the stars and gas in all the galaxies we see make up only a small fracton of what is truly out there. The rest seems to be made of something scientists have named "dark matter", matter which neither emits nor absorbs light, so that we cannot observe it directly. Which of course makes mapping it that much more difficult.

The CFHTLenS team, led by Catherine Heymans of the University of Edinburgh and Ludovic Van Waerbeke of the University of British Columbia in Canada, has nevertheless managed this feat. Capitalising on the fact that gravity actually bends light, the team has studied more than 10 million galaxies in four patches of sky, and recorded the minute distortions induced by the dark matter between us and them. These distortions have then been combined to give us a clear picture of exactly where the dark matter is located.

Not only does this map, which is a hundred times larger than its biggest predecessor, fire the imagination, it also supports the currently most widely-accepted model of how the Universe works. As Dr Heymans told BBC News,

Our theories of dark matter say that it should form a giant intricate cosmic web, and that's exactly what we see in this data, a cosmic web that's housing the galaxies that we can see.

These hot results have caused a minor media storm through outlets such as ABC, Fox News, The Telegraph, Universe Today, Huffington Post and even The Daily Mail. There has also been a fair amount of excitement amongst the 2200 leading astronomers who, along with us, attended last week's 219th meeting of the American Astronomical Society in Austin, US. This year's Cannon Prize winner, Rachel Mandelbaum, says that

[The results] are important in themselves, but they're also important as a proof-of-concept for the future, allowing us to see how powerful these methods will be with other data sets to do additional work.

As an example, a new and larger data set is currently being taken using the Very Large Telescope's (VLT) Survey Telescope in Chile. The triumphs of the CFHTLenS team and the expertise accumulated will, in the near future, be applied to this new project, in which Oxford University is also involved. The principal investigator, Koen Kuijken of Leiden University, said:

Over the next three years we will image more than 10 times the area mapped by CFHTLenS, bringing us ever closer to our goal of understanding the mysterious dark side of the Universe.

Categories: news | cosmology | dark matter | weak lensing | velander | miller