This week NASA announced three new findings revealed by images from its Hubble Space Telescope: the deepest image ever obtained of a galaxy cluster, four super-bright galaxies as they appeared 13 billion years ago, and a sample of small galaxies previously too faint and distant to be seen, which are thought to be responsible for most of the stars we see in the skies today. Here are some of the images which made these discoveries possible.
The Frontier Fields is a multi-year program using NASA’s Hubble and Spitzer Space telescopes and the Chandra X-ray Observatory to peer deep into the universe. Astronomers are exploiting a phenomenon called gravitational lensing, a sort of celestial zoom lens, where the gravitational pull of massive galaxy clusters warp space so that objects beyond them appear magnified up to 20 times. The Frontier Fields program will focus on six such galaxy clusters and will be also be used to trace the distribution of the invisible dark matter, which accounts for the bulk of the universe's mass, within those clusters.
This composite image taken by the Hubble Space Telescope takes advantage of gravitational lensing to use the immense gravity of the foreground galaxy cluster Abell 2744, commonly known as Pandora's Cluster, to capture the deepest ever view of a galaxy cluster. It shows almost 3,000 background galaxies as they would have appeared 12 billion years ago, not long after the Big Bang. The image shows some of the faintest and youngest galaxies ever detected in space. Without gravitational lensing, most of these background galaxies would be invisible.
This composite of Hubble images shows several ultra-bright young galaxies from 13 billion years ago. The four circled red objects—which appear red because their light has been stretched to longer infrared wavelengths by the expansion of the universe—are captured as they would have appeared a mere 500 million years after the Big Bang. These bright young galaxies are only one-twentieth the size of our own galaxy the Milky Way, but the brightest one is forming stars approximately 50 times faster.
These ultra-bright, young galaxies are 10 to 20 times more luminous than any objects from the same era which have previously been observed. Their star-making prowess and compact size makes them brighter than their contemporaries. The Hubble images enabled astronomers to measure star-formation rates and sizes for these galaxies. Using the Spitzer telescope, the astronomers were also able to estimate the stellar masses of the stars within the galaxies, by measuring their total stellar luminosity.
Between 9 billion and 12 billion years ago, the universe experienced a baby boom of star formation, but until now most of the galaxies which gave birth to the stars we see every night were too small and faint to be observed. In this ultraviolet image Hubble has captured a sample of 58 small, young galaxies, which are 100 times fainter than those typically detected in previous deep-field surveys of the early universe, as they would have appeared 10 billion years ago. There are 100 times more of these smaller, fainter galaxies than of their more flashy, brighter cousins, making these galaxies are the smallest, faintest, and most numerous ever seen in the remote universe.
NASA's Hubble Space Telescope was launched in 1990 and is the first major optical telescope to be placed in space. Since then it has captured more than 570,000 images of 30,000 celestial objects. Hubble has helped to discover dark energy, determine the age of the universe, and capture the the deepest views of the cosmos.