SDSS J1138+2754, a galaxy cluster located approximately 5 billion light-years away in the constellation Leo, is so massive that its gravity distorts, brightens, and magnifies light from more distant galaxies behind it, an effect called gravitational lensing.
This image, taken by Hubble’s Wide Field Camera 3 (WFC3), shows the massive galaxy cluster SDSS J1138+2754. Image credit: NASA / ESA / Hubble / Judy Schmidt, www.geckzilla.com.
Galaxy clusters contain thousands of galaxies of all ages, shapes and sizes.
Typically, they have a mass of about one million billion times the mass of the Sun. They form over billions of years as smaller groups of galaxies slowly come together.
At one point in time they were believed to be the largest structures in the Universe — until they were usurped in the 1980s by the discovery of superclusters, which typically contain dozens of galaxy clusters and groups and span hundreds of millions of light-years.
However, clusters do have one thing to cling on to; superclusters are not held together by gravity, so galaxy clusters still retain the title of the biggest structures in the Universe bound by gravity.
A large mass of the galaxy cluster SDSS J1138+2754 is creating such a strong gravitational field that it is bending the very fabric of its surroundings.
This causes the billion-year-old light from galaxies sitting behind it to travel along distorted, curved paths, transforming the familiar shapes of spiral and elliptical galaxies (visible in other parts of the image) into long, smudged arcs and scattered dashes.
Some distant galaxies even appear multiple times in this Hubble image.
Since galaxies are wide objects, light from one side of the galaxy passes through the gravitational lens differently than light from the other side.
When the galaxies’ light reaches Earth it can appear reflected, as seen with the galaxy on the lower left part of the lens, or distorted, as seen with the galaxy to the upper right.
These data were taken as part of a research project on star formation in the distant Universe, building on Hubble’s extensive legacy of deep-field images. Hubble observed 73 gravitationally-lensed galaxies for this project.
