The image from the Hubble Space Telescope shows a group of hundreds of galaxies that are 7.5 billion light-years distant from us. The brightest is called SDSS J1156 + 1911 and is known as the brightest galaxy in the cluster (in the center from the bottom). Found in the program Sloanovskogo search giant arcs. In total, more than 70 galaxies were recorded in the search, which are strongly influenced by gravitational lensing.
Gravitational lensing is one of the predictions of Einstein’s general theory of relativity. The mass in the galaxy is so huge that it can actually bend the fabric of the environment (space-time), forcing the light to move along curved lines. As a result, the image of a more distant galaxy seems distorted and enlarged for the observer. This effect plays into the hands of astronomers, allowing you to see distant galaxies. Galactic clusters are scale structures containing from hundreds to thousands of galaxies with a mass that is billions of times larger than solar. SDSS J1156 + 1911 mass reaches 600 billion solar, which is less massive than the average galaxy. But the mass is enough to create a fuzzy green stripe, seen just below the brightest galaxy.