Space is a truly fascinating place, filled to the brim with awe-inspiring, godlike entities such as stars, planets, comets, nebulas, and so much more that takes our collective breath away every time we look up at the night sky. However, these things we can see only make up about 20 percent of the universe. So, what about those parts of space that we cannot observe, that other 80 percent? This would be what scientists call “dark matter”, defined as “non-luminous material that is postulated to exist in space and that could take any of several forms including weakly interacting particles ( cold dark matter ) or high-energy randomly moving particles created soon after the Big Bang ( hot dark matter )”. In other words, the gaps in between all that is observable in the universe, the things we cannot see, the structures that seemingly tie together galaxies across the universe. Since its very existence runs off of an assumption, as well as the fact that it does not give off, reflect, or absorb light, dark matter is very difficult to observe.
However, researchers now say that they have produced the first composite image of the dark matter that connects galaxies. Mike Hudson, a professor of astronomy at the University of Waterloo, says the image “moves us beyond predictions to something we can see and measure.” Hudson is also the co-author of a new study published in the Monthly Notices of the Royal Astronomical Society.
The researchers employed a technique called “weak gravitational lensing”, which is a statistical measurement of the bends that happen in the path of light passing near mass. This, in turn, produces illustrations of galaxies that are warped by dark matter or other celestial masses.
In order to study the weak signal in the dark, they required two different pieces of data: a catalog of galaxy cluster pairs that were lensed, and a catalog of background source galaxies with accurate distance measurements. They combined lensing data from sky surveys over multiple years. They then combined more than 23,000 pairs of galaxies, all of which are about 4.5 billion light-years away. This enabled them to create a map of the presence of dark matter between the galaxies. The filament on their map is the average of all 23,000 galaxy pairs.