Galaxies included in the cluster at an early stage of its formation. Image : NASA, ESA, CSA, T. Morishita (IPAC). Image processing: A. Pagan (STScI)
The James Webb telescope, which systematically explores the "young years" of our universe, has for the first time made out a cluster of galaxies at the stage of formation. The findings were published in The Astrophysical Journal Letters.
The age of galaxies in the protocluster is only 650 million years after the Big Bang (the age of the Universe is about 13.8 billion years). So far, there are only seven galaxies in the cluster, but scientists are sure that they are observing the "childhood" years of the real giant. Using spectral data, they were able to calculate the dynamics of the protocluster up to the present day. Such a calculation, based on observations, makes it possible to predict that the cluster will absorb many galaxies during its evolution.
A cluster of galaxies is a group of galaxies connected by gravitational interaction. Such clusters of galaxies are among the largest objects in the universe that can be considered as a single entity. The largest of these, the Coma Cluster, contains over a thousand galaxies. Observation of it at one time allowed astronomers to come to the conclusion that for a satisfactory description of the trajectories of celestial bodies, luminous matter is not enough: in order for their orbits to comply with the laws of universal gravitation, it is necessary to introduce additional “black” matter that has mass, but is invisible through a telescope.
Galaxy clusters act like gravitational lenses. When light passes near such a cluster, the direction of its rays changes. This can give magnified and deformed images of more distant objects that are behind it. Scientists also saw the protocluster through such a lens, since one "James Webb" would not be enough to see such a distant object. This lens was another cluster of galaxies – Pandora.
The galaxies that make up the protocluster have been identified as possible targets in the early universe in observations by the Hubble Space Telescope. However, his capabilities in the infrared range were severely limited (he only saw the near infrared range), so image detail and accurate redshift measurements were not available to him, unlike "James Webb".
It took precise measurements from the James Webb spectrometric instrument to find out that the protocluster galaxies are moving at a tremendous speed – about 1000 km / s – around their common region of black matter, and to measure the distances between them.
Before the advent of "James Webb" it was impossible to look into the deep past of clusters of galaxies. This was due to the fact that clusters of galaxies far from us are visible at higher and higher redshifts due to the expansion of the Universe, which means that they require observations in the infrared range, in which there were no instruments of this accuracy class. With the advent of "James Webb", whose infrared instruments were specially designed for this purpose, this problem was solved.
A team of astronomers who discovered a protocluster of galaxies awaits the launch of the Nancy Grace Roman Space Telescope. It will make it possible to take large (200 times larger than Hubble's area) surveys of the sky in the infrared range with high resolution to identify candidates for protoclusters of galaxies. Next, James Webb will study the candidates with its precise spectroscopic instruments. The launch of the Nancy Grace Roman telescope is scheduled for 2027.