The explanation we name darkish matter darkish is not as a result of it is some shadowy materials. It is as a result of darkish matter does not work together with gentle.
The distinction is delicate, however necessary. Common matter will be darkish as a result of it absorbs gentle. It is why, for instance, we are able to see the shadow of molecular clouds in opposition to the scattered stars of the Milky Method. That is doable as a result of gentle and matter have a option to join.
Mild is an electromagnetic wave, and atoms include electrically charged electrons and protons, so matter can emit, soak up and scatter gentle. Darkish matter is not electrically charged. It has no option to join with gentle, and so when gentle and darkish matter meet up they merely move by one another.
All of our observations counsel that darkish matter and lightweight solely have gravity in widespread.
When darkish matter is clustered round a galaxy, for instance, its gravitational tug can deflect gentle. Due to this we are able to map the distribution of darkish matter within the Universe by observing how gentle is gravitationally lensed round it.
We additionally know that darkish and common matter work together gravitationally. The tug of darkish matter causes galaxies to collect collectively into superclusters.
However an unanswered query is whether or not darkish and common matter solely work together gravitationally. If an atom and darkish matter particle intersected, would they actually simply move by one another?
Since we’ve not straight noticed darkish matter particles we are able to solely speculate, however most darkish matter fashions argue that gravity is the one widespread hyperlink with gentle and common matter. Darkish and common matter clump round one another, however they do not collide and merge like interstellar clouds.
However a new examine suggests the 2 do work together, which may reveal delicate elements of the mysterious stuff.
The examine seems at six ultrafaint dwarf galaxies, or UFDs. They’re satellite tv for pc galaxies close to the Milky Method that appear to have far fewer stars than their mass would counsel.
It’s because they’re principally manufactured from darkish matter. If common and darkish matter solely work together gravitationally, then the distribution of stars in these small galaxies ought to comply with a sure sample. If darkish and common matter work together straight, then this distribution will likely be skewed.
To check this the workforce ran laptop simulations of each situations. They discovered that within the non-interacting mannequin the distribution of stars ought to change into extra dense within the middle of the UFDs and extra diffuse on the edges.
Within the interacting mannequin the stellar distribution needs to be extra uniform. After they in contrast these fashions with observations of the six galaxies, they discovered the interacting mannequin was a barely higher match.
A comparability of non-interacting and interacting darkish matter. (Gabriel Pérez)
So it appears darkish and common matter work together in methods past their gravitational tugs.
There is not sufficient knowledge to pin down the precise nature of the interplay, however the reality there may be any interplay in any respect is a shock.
It implies that our conventional fashions of darkish matter are a minimum of partly flawed. It might additionally level the best way towards new strategies of detecting darkish matter straight. In time we might lastly resolve the thriller of this darkish, however not completely invisible, materials.
This text was initially printed by Universe As we speak. Learn the authentic article.
