NASA's newest space telescope has beamed back its sharpest images yet of a massive galaxy cluster 4.5 billion light-years from Earth, and astronomers say the pictures are already changing what they thought they knew about the early universe.
The images show hundreds of galaxies packed into a single frame, with thin arcs of light bent around the cluster's enormous gravity — a natural effect called gravitational lensing that lets scientists see even more distant objects hiding behind it.
Galaxy clusters are the largest structures in the universe held together by gravity. By studying how this cluster bends light, researchers can map its dark matter — the invisible material that makes up most of its mass but has never been directly observed.
The telescope's infrared instruments can also see through dust that blocks older telescopes, revealing young stars forming inside galaxies that were previously hidden.
In the first release, the team catalogued dozens of new lensed arcs and several candidate galaxies from the universe's first billion years. Follow-up observations are scheduled over the coming months, and the full data set has been made public so research groups worldwide can work on it.
NASA says the telescope is performing better than its design targets, with enough fuel and instrument life for a mission lasting well beyond a decade. More deep-field images are expected early next year.
How far away is the galaxy cluster? About 4.5 billion light-years, meaning the light in the images left the cluster when the universe was roughly two-thirds of its current age.
What is gravitational lensing? When a massive object sits between Earth and a distant galaxy, its gravity bends the distant galaxy's light like a lens, magnifying it and sometimes stretching it into arcs.
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