Dark matter was first detected in the 1930s, thanks to its gravitational effects on ordinary, visible matter.
To see which bits of it are dark matter simply requires superimposing the known pattern of visible matter.
ECONOMIST: Cosmology: I spy with my little gravitational lens | The
Indeed, the distribution of mass through the galaxy roughly followed the distributions of visible matter, with no need for exotic new particles.
The visible matter in the universe (stars) adds up to less than 5 percent of the total mass that is known to exist from many other observations.
FORBES: Endeavour's Final Liftoff Takes Antimatter Detector Into Space
Most galaxies rotate at a speed that should cause them to fly apart if all that holds their visible matter together is gravity as physicists understand it.
Since dark matter is very massive indeed (there is about six times as much of it around as there is visible matter) it makes good gravitational lenses.
ECONOMIST: Cosmology: I spy with my little gravitational lens | The
Since both are affected by gravity they are attracted to each other, so the distribution of normal, visible matter acts as a proxy for the distribution of dark matter.
Two further refinements were necessary: to work out the third dimension distance from Earth and to subtract the effect of visible matter in order to be left with the distribution of dark matter pure and simple.
ECONOMIST: Cosmology: I spy with my little gravitational lens | The
They think the universe is stuffed with invisible dark matter composed of particles very different from the ones that make up visible matter, and it is the gravity of this dark matter that holds galaxies together.
Their overlap confirms the hypothesis that dark matter is the skeleton upon which visible matter is supported, and also lends weight to a second idea that galaxies form where dark matter accumulates at high densities, pulling visible matter with it.
ECONOMIST: Cosmology: I spy with my little gravitational lens | The
It could also cast light on the mystery of dark matter, a substance that pervades the universe in vastly larger quantities than familiar, visible matter, but whose existence can be inferred only by watching its gravitational effect on visible matter.
Dark and visible matter usually coincide.
ECONOMIST: Cosmology: I spy with my little gravitational lens | The
But it lacks any visible subject matter: no discernible woman, nary a mandolin.
In addition, it distributed vials containing a steroid that was contaminated with "visible black particulate matter" later identified as fungus, according to a report from the Massachusetts Board of Registration in Pharmacy.
Dr Massey and his colleagues were able to map the matter (both dark and visible) in the bit of the firmament covered by the Cosmic Evolution Survey by looking for characteristic distortions in the shape of distant galaxies that only Hubble, which is beyond the image-blurring effects of the atmosphere, can see.
ECONOMIST: Cosmology: I spy with my little gravitational lens | The
Indeed, one principal purpose of the Bolshoi simulation is to compute and model the evolution of dark matter halos thereby rendering the invisible visible for astronomers to study, and to predict structures that astronomers could then seek to observe.
应用推荐