The James Webb Space Telescope recently observed what is called in jargon “intracluster light” (ICL)or the very weak emission produced by the stars of their galaxies as they interact within a cluster.
“In this study we show the great potential of JWST for the observation of such a faint object“, said Mireia Montes, lead author of the article, in a statement from the Instituto de Astrofísica de Canarias. “This will allow us to study galaxy clusters that are much further away and in much more detail.“
The observation of this light, in fact, has great implications not only for understand the evolution of galaxies and clusters of galaxies, but also for a mystery crucial to our entire understanding of the cosmos. Despite Webb’s power, the discovery comes not just from direct observations, but rather from in-depth study.
This light is still extremely faint, and the galaxies in the cluster are extremely bright. “Analyzing this scattered light, we discover that the inner parts of the cluster are formed by the merger of massive galaxies, while the outer parts are due to the accretion of galaxies similar to our Milky WayMontes continues.
An important role is also given by dark matter (also present inside the room you are in) which interacts only gravitationally. In a galaxy cluster, with hundreds if not thousands of galaxies, this mysterious matter spreads through and around… and this “ghostly light” is just one way to track it!