As the evidence for dark matter builds, astronomers have begun modelling how it ought to be distributed around the cosmos. They’ve shown how it must be distributed on the largest scale to make clusters of galaxies form in the way we see, various other simulations show that it forms a kind of halo around galaxies such as the Milky Way.
But what of smaller scales? Today, Ethan Siegel and his student Xiaoying Xu at the University of Arizona produce the first model showing how much dark matter there is in the Solar System.
They say that throughout its 4.5 billion year history, the Sun will have been sweeping up the dark stuff as it has moved through the Milky Way. Siegel estimates that in this time it will have gathered some 8 x10^19 kilograms of dark matter, or about 300 times the background levels in the Milky Way.
That’s a lot of mass and Siegel points out that that much dark matter should have profound implications for the various teams searching for it. It means there ought to be more dark matter than anybody expected although this will have a smaller velocity relative to Earth because it should be moving through the galaxy with the Sun. Keep ‘em peeled, guys.
It’s also easy to think that this much dark matter might have a bearing on the Pioneer anomaly, the unexplained acceleration towards the Sun of our most distant space probes. But no, says Siegel.
This amount of dark matter is much several orders of magnitude smaller than than the mass of Pluto or any of the larger moons in the solar system. So there’s not nearly enough to explain the observed accelerations, he concludes.
So that’s that then.
Ref: arxiv.org/abs/0806.3767: Dark Matter in the Solar System