Scientists at Kindai University in Japan have made the most detailed measurement yet of the distribution of dark matter using the curvature of space-time around a massive object. Led by cosmologist Kaiki Taro Inoue, the team used a gravitational lens to map the elusive substance on an incredibly small scale – with a resolution of just 30,000 light-years. While this might sound large, when compared to the size of the Milky Way at 100,000 light-years across, it is an impressive feat. The researchers were able to map something that cannot even be seen down to a scale less than a third the size of our galaxy, over a distance of more than 7.5 billion light-years.
The analysis of dark matter relied on a fortuitous alignment of cosmic objects called a gravitational lens. Just as a trampoline curves beneath your body’s weight, space-time curves around massive objects. Similarly, if light encounters the curved space-time around a massive object, it becomes distorted and magnified. By studying these distorted and smeared light patterns, scientists can not only study the distant galaxies behind the lens in greater detail but also reveal the distribution of gravity in the foreground lens.
This method is particularly useful for discovering the hiding places of dark matter. Dark matter cannot be directly detected as it emits no light, but its presence can be inferred from the excess gravity it creates. By subtracting all the normal matter, such as galaxies, from the decoded distribution of mass, scientists are left with the dark matter.
Inoue and his team used a gravitationally lensed galaxy known as MG J0414+0534 to demonstrate this technique. The galaxy is so far away that its light has taken 11.3 billion years to reach us. By analyzing the lensed images of the galaxy, the researchers were able to subtract the effects of the visible portions of the lens galaxy and produce a detailed map of the dark matter.
The resulting map supports the theory that dark matter is distributed in clumps both within galaxies and in the spaces between them, as predicted by the theory of cold dark matter. This research provides a powerful new tool for understanding dark matter, as previous limitations in resolving its distribution on smaller scales have hindered scientists’ efforts to study its properties. By being able to study dark matter on a smaller scale, researchers hope to narrow down the possibilities for identifying the mysterious mass.
The findings of this research have been published in The Astrophysical Journal, offering a significant step forward in our understanding of dark matter and its distribution across the universe.