Astronomers working with data from the space telescope unveiled Thursday what they are calling the deepest infrared image ever captured of a protoclusters — a vast, still-forming superstructure that will eventually grow into one of the largest gravitationally bound objects in the universe. The image, which required 47 hours of cumulative exposure time, reveals more than 1,800 individual galaxies crowded into a region of the sky that, as seen from Earth, is smaller than a grain of sand held at arm's length.
The supercluster is located at a redshift corresponding to a look-back time of approximately 11.2 billion years, meaning the light captured in the image left those galaxies when the universe was less than 20% of its current age. At that early epoch, galaxy formation was proceeding at a furious pace, and massive structures were assembling through gravity at rates that still challenge theoretical models to fully explain.
"What we're seeing is essentially the universe under construction," said the principal investigator of the observing team. "These galaxies are forming stars at a rate hundreds of times faster than our own Milky Way does today. They're crashing into each other, merging, exchanging gas. It's chaos — magnificent, illuminating chaos."
"These galaxies are forming stars at a rate hundreds of times faster than our own Milky Way does today. What we're seeing is the universe under construction."
— Principal investigator, space telescope observing program
The image was made possible by the telescope's near-infrared camera, which can detect the highly redshifted light of the most distant objects in the universe — light that has been stretched to wavelengths invisible to human eyes and to previous generations of space telescopes. Infrared sensitivity is essential for studying the early universe because the expansion of space stretches visible light into the infrared portion of the spectrum over billions of years of travel.
Scientists say the new data will help them test competing theories about how galaxy clusters form and grow, and will provide statistical constraints on the large-scale distribution of dark matter in the early universe. Hundreds of archival datasets from the telescope are still waiting to be analyzed, and astronomers expect a cascade of discoveries over the coming years as computational tools capable of processing the unprecedented volume of imagery continue to improve.