Using observations from the James Webb Space Telescope covering a patch of sky roughly three times the area of the full moon, scientists have created the most detailed cosmic map to date of dark matter, which constitutes most of the material filling the universe.
Ordinary matter forms stars, planets, humans, and everything else we can see, but it accounts for only about 15% of the matter in the universe. The remainder is dark matter, which does not emit or reflect light, making it invisible to the human eye and to telescopes.
Scientists infer its existence based on the gravitational effects it exerts on a large scale, such as the rotation speed of galaxies, how galaxies hold together, and how light from distant objects is bent as it passes through massive cosmic structures.
The new map of dark matter distribution from the James Webb Telescope is based on the phenomenon of gravitational lensing, which causes subtle distortions in the shapes of nearly 250,000 distant galaxies due to the gravitational effects of matter along the line of sight. The previous dark matter map was based on observations from the Hubble Space Telescope.
Dark Matter: The Hidden Force
The new map, supported by the greater capabilities of the James Webb Telescope, offers twice the resolution of the previous map. It covers larger areas of the universe and probes further back in time, essentially looking at what happened approximately 8 to 10 billion years ago, a key period for galaxy formation.
It was stated that “This allows us to find a solution for the finer structures of dark matter, discover mass concentrations that were not previously visible, and extend dark matter mapping to earlier epochs of the universe.”
The map reveals with unprecedented clarity new details of the large-scale structure of the universe, known as the cosmic web. This consists of galaxy clusters and immense filaments built from dark matter, along which galaxies and gases are distributed, as well as regions of lower mass density.
James Webb Redraws the Cosmic Web
The James Webb Telescope was launched in 2021 and operates in the infrared. It has a light-gathering power about six times greater than the Hubble Telescope and began operations in 2022.
It was noted that the James Webb Telescope is like putting on a new pair of glasses to see the universe; it sees fainter, more distant galaxies with greater clarity than ever before.
It was added that this “effectively gives us a denser network of more distant galaxies to work with, which is exactly what we want for this type of study. Detecting more galaxies and obtaining clearer images directly translates into a sharper map of dark matter.”
The new map covers a portion of the sky called the Cosmic Evolution Survey, or “COSMOS,” located in the direction of the Sextans constellation. Researchers stated that the map will facilitate future explorations of the universe in many ways.
