Astronomers need to be especially smart to map the invisible dark matter in the universe. Recently, a team of researchers improved an existing technique so that it can see up to ten times better in the dark.
Dark matter is frustratingly difficult to measure. It's completely invisible: it just doesn't interact with light (or normal matter) in any way, shape, or shape. We know, however, that dark matter exists because of its gravitational influence on everything around it – including the normal matter that stars and galaxies are made up of.
Take a look at the gravitational lens as an example. A massive object, whether made of dark or normal matter, bends the path of any light that passes nearby. It's usually an incredibly small effect, but it's definitely measurable. For example, we can see the lens of starlight around the sun, which is why we knew that Einstein's general theory of relativity must be correct.
When light from a very distant galaxy passes through or near a somewhat less distant massive object such as a cluster of galaxies, that light is bent. We can use this distortion to measure the amount of dark matter in the galaxy cluster, and it is one of our main methods of mapping dark matter in the universe.
Usually we don't get this kind of happy alignment. Instead, we have to turn to another technique: a weak gravitational lens. To make this work, astronomers examine a number of galaxies, looking for tiny little distortions in each. Individually it is not much, but together it can provide a map of a large region of dark matter.
Recently, a team of astronomers improved on this idea by adding the rotation of the galaxies under observation, as reported in an article recently published in the Royal Astronomical Society's Monthly Notices.
Since we know how galaxies should rotate, we can combine the distortions in their shapes with the distortions in their internal movements to give the observation goat a lot more bang, resulting in a technique that can map dark matter up to ten times more can be used as forms alone.