Millions of galaxies populate the patch of sky known as the COSMOS field, short for Cosmic Evolution Survey, a portion of which is shown here. Even the smallest dots in this image are galaxies, some up to 12 billion light-years away. The square region in the center of bright objects is where the telescope was blinded by bright light. However, even these brightest objects in the field are more than ten thousand times fainter than what you can see with the naked eye. The picture is a combination of infrared data from Spitzer (red) and visible-light data (blue and green) from Japan's Subaru telescope atop Mauna Kea in Hawaii. These data were taken as part of the SPLASH (Spitzer large area survey with Hyper-Suprime-Cam) project.

NASA's Spitzer Space Telescope has teamed up with the Hubble Space Telescope to conduct the Spitzer UltRaFaint Survey, or SURFS UP. The joint project is catching sight of a "wave" of galaxies that emerged in the early universe. Starlight from these primordial galaxies is reckoned to have cleared a fog of hydrogen gas that shrouded the cosmos during a mysterious period known as the Dark Ages. SURFS UP will image 10 massive, foreground galaxy clusters, whose strong gravity magnifies the light of background objects. This so-called cosmic lensing causes objects such as the distant, dim, young galaxies that SURFS UP is investigating, to appear more than 10 times brighter than they normally would, allowing the team to study the stars within them. This image exhibits the magnifying effects of two of the galaxy clusters, the Bullet Cluster and MACS 1149. The zoom-in circles show ultra-distant galaxies that SURFS UP has revealed. The overall reddish hue of starlight visible to Spitzer in these distant galaxy indicates that the stars in these young galaxies are already mature. The findings therefore push back the time when the first stars and galaxies arose and began illuminating the Dark Ages. The Spitzer observations, in infrared, reveal key characteristics, such as mass and ages, about older populations of stars in the far-off galaxies. Besides finding the galaxies in the first place, Hubble's observations, in visible light, speak to the formation rate of young stars. Taken together, the data paint a richly detailed portrait of galactic evolution and its effect on the wider cosmos. These Spitzer observations at wavelengths of 3.5 and 4.6 microns are shown in blue and red, respectively. They were obtained during Spitzer's warm mission phase, following the depletion of its liquid coolant in 2009.

This image shows two clusters of galaxies colliding with one another, the smaller one being known as the Bullet Cluster. NASA's Spitzer Space Telescope obtained these observations during the telescope's warm mission phase, following the depletion of its liquid coolant in 2009. Spitzer, along with the Hubble Space Telescope, targeted the Bullet Cluster as part of the Spitzer UltRaFaint Survey, or SURFS UP. The joint project will image 10 massive, foreground galaxy clusters whose strong gravity magnifies the light of background objects. This so-called cosmic lensing causes objects such as the distant, dim, young galaxies that SURFS UP is investigating, to appear more than 10 times brighter than they normally would, allowing the team to study the stars within them. At least one distant, young galaxy has been detected far behind the bullet cluster but magnified by its gravitational lens effect. The overall reddish hue of starlight visible to Spitzer in this distant, young galaxy indicates that the stars in it are already mature. The findings therefore push back the time when the first stars and galaxies arose and began ending a cosmic period known as the Dark Ages. These Spitzer observations at wavelengths of 3.5 and 4.6 microns are shown in blue and red, respectively.

NASA's Spitzer Space Telescope captured this image of the galaxy cluster MACS 1149. The observations took place during the telescope's warm mission phase, following the depletion of its liquid coolant in 2009. Spitzer, along with the Hubble Space Telescope, targeted MACS 1149 as part of the Spitzer UltRaFaint Survey, or SURFS UP. The joint project will image 10 massive, foreground galaxy clusters whose strong gravity magnifies the light of background objects. This so-called cosmic lensing causes objects such as the distant, dim, young galaxies that SURFS UP is investigating, to appear more than 10 times brighter than they normally would, allowing the team to study the stars within them. At least one distant, young galaxy has been detected far behind the MACS 1149 but magnified by its gravitational lens effect. The overall reddish hue of starlight visible to Spitzer in this distant, young galaxy indicates that the stars in it are already mature. The findings therefore push back the time when the first stars and galaxies arose and began ending a cosmic period known as the Dark Ages. These Spitzer observations at wavelengths of 3.5 and 4.6 microns are shown in blue and red, respectively.

This image shows a portion of our sky, called the Botes field, in infrared light. Using Spitzer, researchers were able to detect this background glow, which spreads across the whole sky, by masking out light from galaxies and other known sources of light. The scientists find that this light is coming from stray stars that were torn away from galaxies. When galaxies tangle and merge -- a natural stage of galaxy growth -- stars often get kicked out in the process. The stars are too faint to be seen individually, but Spitzer may be seeing their collective glow.

This image shows a mysterious, background infrared glow captured by NASA's Spitzer Space Telescope. Using Spitzer, researchers were able to detect this background glow, which spreads across the whole sky, by masking out light from galaxies and other known sources of light (the masks are the gray, blotchy marks). The scientists find that this light is coming from stray stars that were torn away from galaxies. When galaxies tangle and merge -- a natural stage of galaxy growth -- stars often get kicked out in the process. The stars are too faint to be seen individually, but Spitzer may be seeing their collective glow.

The image on the left shows a portion of our sky, called the Botes field, in infrared light, while the image on the right shows a mysterious, background infrared glow captured by NASA's Spitzer Space Telescope in the same region of sky. Using Spitzer, researchers were able to detect this background glow, which spreads across the whole sky, by masking out light from galaxies and other known sources of light (the masks are the gray, blotchy marks). The scientists find that this light is coming from stray stars that were torn away from galaxies. When galaxies tangle and merge -- a natural stage of galaxy growth -- stars often get kicked out in the process. The stars are too faint to be seen individually, but Spitzer may be seeing their collective glow.

Astronomers using NASAs Spitzer Space Telescope have greatly improved the cosmic distance ladder used to measure the expansion rate of the universe, as well as its size and age. The cosmic distance ladder, symbolically shown here in this artist's concept, is a series of stars and other objects within galaxies that have known distances. By combining these distance measurements with the speeds at which objects are moving away from us, scientists can calculate the expansion rate of the universe, also known as Hubble's constant. Spitzer was able to improve upon past measurements of Hubble's constant due to its infrared vision, which sees through dust to provide better views of variable stars called Cepheids. These pulsating stars are vital "rungs" in the distance ladder. Spitzer observed ten Cepheids in our own Milky Way galaxy and 80 in a nearby neighboring galaxy called the Large Magellanic Cloud. Without the cosmic dust blocking their view at the infrared wavelengths seen by Spitzer, the research team was able to obtain more precise measurements of the stars' apparent brightness, and thus their distances. With these data, the researchers could then tighten up the rungs on the cosmic distant ladder, better determining distances to other galaxies, and calculate a new and improved estimate of our universe's expansion rate. The galaxies used in this composite artwork are all infrared images from Spitzer covering wavelengths of 3.6 microns (blue), 4.5 microns (green), and 8.0 microns (red).

With the combined power of NASA's Spitzer and Hubble space telescopes, as well as a cosmic magnification effect, astronomers have spotted what could be the most distant galaxy ever seen. Light from the primordial galaxy traveled approximately 13.2 billion light-years before reaching NASA's telescopes, shining forth from the so-called cosmic dark ages when the universe was just 3.6 percent of its present age. Astronomers relied on gravitational lensing to catch sight of the early, distant galaxy. In this phenomenon, predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects. At the center we see light from the newfound galaxy MACS 1149-JD. these visible and infrared light images from Hubble, MACS 1149-JD looks like a dim, red speck. The small galaxy's starlight has been stretched into longer wavelengths, or "redshifted," by the expansion of the universe. MACS 1149-JD's stars originally emitted the infrared light seen here at much shorter, higher-energy wavelengths, such as ultraviolet. The far-off galaxy existed within an important era when the universe transformed from a starless expanse during the dark ages to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy opens a window onto the deepest, remotest epochs of cosmic history.

With the combined power of NASA's Spitzer and Hubble space telescopes, as well as a cosmic magnification effect, astronomers have spotted what could be the most distant galaxy ever seen. Light from the primordial galaxy traveled approximately 13.2 billion light-years before reaching NASA's telescopes, shining forth from the so-called cosmic dark ages when the universe was just 3.6 percent of its present age. Astronomers relied on gravitational lensing to catch sight of the early, distant galaxy. In this phenomenon, predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects. In this image, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times (though it is not readily apparent in this view).

With the combined power of NASA's Spitzer and Hubble space telescopes, as well as a cosmic magnification effect, astronomers have spotted what could be the most distant galaxy ever seen. Light from the primordial galaxy traveled approximately 13.2 billion light-years before reaching NASA's telescopes, shining forth from the so-called cosmic dark ages when the universe was just 3.6 percent of its present age. Astronomers relied on gravitational lensing to catch sight of the early, distant galaxy. In this phenomenon, predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects. At the center we see light from the newfound galaxy MACS 1149-JD. these visible and infrared light images from Hubble, MACS 1149-JD looks like a dim, red speck. The small galaxy's starlight has been stretched into longer wavelengths, or "redshifted," by the expansion of the universe. MACS 1149-JD's stars originally emitted the infrared light seen here at much shorter, higher-energy wavelengths, such as ultraviolet. The far-off galaxy existed within an important era when the universe transformed from a starless expanse during the dark ages to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy opens a window onto the deepest, remotest epochs of cosmic history.

With the combined power of NASA's Spitzer and Hubble space telescopes, as well as a cosmic magnification effect, astronomers have spotted what could be the most distant galaxy ever seen. Light from the primordial galaxy traveled approximately 13.2 billion light-years before reaching NASA's telescopes, shining forth from the so-called cosmic dark ages when the universe was just 3.6 percent of its present age. Astronomers relied on gravitational lensing to catch sight of the early, distant galaxy. In this phenomenon, predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects. In the big image at left, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times, bringing the remote object into view. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right. In these visible and infrared light images from Hubble, MACS 1149-JD looks like a dim, red speck. The small galaxy's starlight has been stretched into longer wavelengths, or "redshifted," by the expansion of the universe. MACS 1149-JD's stars originally emitted the infrared light seen here at much shorter, higher-energy wavelengths, such as ultraviolet. The far-off galaxy existed within an important era when the universe transformed from a starless expanse during the dark ages to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy opens a window onto the deepest, remotest epochs of cosmic history.

Astronomers have uncovered the patterns of light that appear to be from the first stars and galaxies that formed in the universe, hidden within a strip of sky observed by NASAs Spitzer Space Telescope. This panel shows Spitzers typical infrared view of this patch, including foreground stars and a confusion of fainter galaxies, at a wavelength of 4.5 microns. Additional processing of this image reveals faint structures in the background that match just what we would expect for the patterns of clusters for the first galaxies formed in the universe. Even though any particular early galaxy would be too faint to see individually, this technique allows astronomers to better understand what things were like shortly after the Big Bang.

Astronomers have uncovered the patterns of light that appear to be from the first stars and galaxies that formed in the universe, hidden within a strip of sky observed by NASAs Spitzer Space Telescope. These two panels show the same slice of sky in the constellation Botes, dubbed the Extended Groth Strip. The area covered is about 1 by 0.12 degrees in angular extent. The top panel shows Spitzers typical infrared view of this patch, including foreground stars and a confusion of fainter galaxies, at a wavelength of 4.5 microns. In the lower panel, all of the resolved stars and galaxies have been masked out of the image (grey patches), and the remaining background glow has been smoothed and enhanced. This processing reveals a structure too faint to be seen in the original image. The structure of the lower panel matches just what we would expect for the patterns of clusters for the first galaxies formed in the universe. Even though any particular early galaxy would be too faint to see individually, this technique allows astronomers to better understand what things were like shortly after the Big Bang.

Astronomers have uncovered the patterns of light that appear to be from the first stars and galaxies that formed in the universe, hidden within a strip of sky observed by NASAs Spitzer Space Telescope. All of the resolved stars and galaxies have been masked out of the image (grey patches), and the remaining background glow has been smoothed and enhanced. This processing reveals a structure too faint to be seen in the original image. The structure in this image matches just what we would expect for the patterns of clusters for the first galaxies formed in the universe. Even though any particular early galaxy would be too faint to see individually, this technique allows astronomers to better understand what things were like shortly after the Big Bang.

This Hubble image shows a field of galaxies, known as the Great Observatories Origins Deep Survey, or GOODS. Visible light taken by its Advanced Camera for Surveys instrument at 0.6 and 0.9 microns is blue and green, respectively, while infrared light captured by Hubble's new Wide Field Camera 3 at 1.6 microns is red.

Astronomers have discovered a massive cluster of young galaxies forming in the distant universe. The growing galactic metropolis, named COSMOS-AzTEC3, is the most distant known massive "proto-cluster" of galaxies, lying about 12.6 billion light-years away from Earth. Members of the developing cluster are shown here, circled in white, in this image taken by Japan's Subaru telescope atop Mauna Kea in Hawaii. The cluster was discovered by a suite of multi-wavelength telescopes, including NASA's Spitzer, Chandra and Hubble space observatories, Subaru and the W.M. Keck Observatory, also atop Mauna Kea in Hawaii. The other dots in this picture are stars or galaxies that are not members of the cluster -- most of the them are located closer to us than the cluster, but some are farther away. The two brightest spots are stars. Though they appear bright in this image, they are actually tens of thousands of times fainter than what we can see with our eyes.

Astronomers have caught sight of an unusual galaxy that, like a lighthouse, has illuminated new details about a celestial "sandbar" connecting two massive islands of galaxies. The galaxy, which is wandering through this sandbar, or filament, has twin lobes of material jetting from its center that are bending backwards as they sweep through the filament's hot gas. The findings are a result of observations made primarily by NASA's Spitzer Space Telescopes and the Very Large Array radio telescope near Socorro, N.M. In this diagram, one of the clusters is shown to the right as a collection of galaxies, which are seen as dots. The hot gas filling the cluster and filament is illustrated with purple. The unusual galaxy and the angle of its bent lobes are illustrated in the callout. In 2008, Spitzer identified this filament, which runs from a galaxy cluster known as Abell 1763. Later, Spitzer data helped narrow in on the unusual galaxy, and led to follow-up radio observations that were that were used to find and measure the angles of the lobes. Astronomers measured the curve of these lobes to gauge the density of particles in the intergalactic filament. Such rare, arced galaxies could be used to find and study the hard-to-see intergalactic filaments that link up galaxy clusters and offer ideal environments for forming new stars. Infrared-bright galaxies measured by Spitzer are represented in the diagram with blue colors, and the brightest "starburst" galaxies are the largest dots. Radio-bright galaxies, including the one sweeping through the filament, are shaded green.

A surprisingly large collections of galaxies (red dots) stands out at a remarkably large distance in this composite image combining infrared and visible-light observations. NASA's Spitzer Space Telescope contributed to the infrared component of the observations, while shorter-wavelength infrared and visible data are provided by Japan's Subaru telescope atop Mauna Kea, Hawaii. Looking out to this distance, the cluster appears as it was 9.6 billion years ago, only about three billion years after the Big Bang. Astronomers were surprised to find such a "modern" cluster at an era when its peers tended to be much smaller, presumably taking billions of more years to collect enough galaxies to reach such a size. Infrared light from Spitzer at wavelengths of 3.6 and 4.5 microns is displayed in red. Subaru observations of near infrared and visible light with wavelengths of 0.9 and 0.44 microns are rendered in green and blue, respectively. The purple overlay is a calculated measure of overall galaxy density and highlights the high concentration of galaxies in the distant cluster.

A long-lost population of active supermassive black holes, or quasars, has been uncovered by NASA's Spitzer and Chandra space telescopes. This image, taken with Spitzer's infrared vision, shows a fraction of these black holes, which are located deep in the bellies of distant, massive galaxies (circled in blue). Spitzer originally scanned the field of galaxies shown in the picture as part of a multiwavelength program called the Great Observatories Origins Deep Survey, or Goods. This picture shows a portion of the Goods field called Goods-South. When astronomers saw the Spitzer data, they were surprised to find that hundreds of the galaxies between 9 and 11 billion light-years away were shining with an unexpected excess of infrared light. They then followed up with X-ray data from Chandra of the same field, and applied a technique called stacking, which adds up the faint light of multiple galaxies. The results revealed that the infrared-bright galaxies are hiding many black holes that had been theorized about before but never seen. This excess infrared light is being produced by the growing black holes. The other smudges in this picture are distant galaxies, most of which are closer to us than the circled galaxies, causing them to appear brighter. This image was taken by Spitzer's multiband imaging photometer at a wavelength of 24 microns. It shows the faintest distant objects ever observed with Spitzer at this wavelength.

Astronomers have unmasked hundreds of black holes hiding deep inside dusty galaxies billions of light-years away. The massive, growing black holes, discovered by NASA's Spitzer and Chandra space telescopes, represent a large fraction of a long-sought missing population. Their discovery implies there were hundreds of millions of additional black holes growing in our young universe, more than doubling the total amount known at that distance. "Active, supermassive black holes were everywhere in the early universe," said Mark Dickinson of the National Optical Astronomy Observatory in Tucson, Ariz. "We had seen the tip of the iceberg before in our search for these objects. Now, we can see the iceberg itself." Dickinson is a co-author of two new papers appearing in the Nov. 10 issue of the Astrophysical Journal. Emanuele Daddi of the Commissariat a l'Energie Atomique in France led the research. The findings are also the first direct evidence that most, if not all, massive galaxies in the distant universe spent their youths building monstrous black holes at their cores. For decades, a large population of active black holes has been considered missing. These highly energetic structures belong to a class of black holes called quasars. A quasar consists of a doughnut-shaped cloud of gas and dust that surrounds and feeds a budding supermassive black hole. As the gas and dust are devoured by the black hole, they heat up and shoot out X-rays. Those X-rays can be detected as a general glow in space, but often the quasars themselves can't be seen directly because dust and gas blocks them from our view. "We knew from other studies from about 30 years ago that there must be more quasars in the universe, but we didn't know where to find them until now," said Daddi.

A long-lost population of active supermassive black holes, or quasars, has been uncovered by NASA's Spitzer and Chandra space telescopes. This image, taken with Spitzer's infrared vision, shows a fraction of these black holes, which are located deep in the bellies of distant, massive galaxies (circled in blue). Spitzer originally scanned the field of galaxies shown in the picture as part of a multiwavelength program called the Great Observatories Origins Deep Survey, or Goods. This picture shows a portion of the Goods field called Goods-South. When astronomers saw the Spitzer data, they were surprised to find that hundreds of the galaxies between 9 and 11 billion light-years away were shining with an unexpected excess of infrared light. They then followed up with X-ray data from Chandra of the same field, and applied a technique called stacking, which adds up the faint light of multiple galaxies. The results revealed that the infrared-bright galaxies are hiding many black holes that had been theorized about before but never seen. This excess infrared light is being produced by the growing black holes. The other smudges in this picture are distant galaxies, most of which are closer to us than the circled galaxies, causing them to appear brighter. This image was taken by Spitzer's multiband imaging photometer at a wavelength of 24 microns. It shows the faintest distant objects ever observed with Spitzer at this wavelength.

These two images show "stacked" Chandra images for two different classes of distant, massive galaxy detected with Spitzer. Image stacking is a procedure used to detect emission from objects that is too faint to be detected in single images. To enhance the signal, images of these faint objects are stacked on top of one another. In both images, low-energy X-rays are shown in orange and high-energy X-rays in blue, and the stacked object is in the center of the image (the other sources beyond the center of the image are X-ray sources that were directly detected and are not part of the source stacking). On the left is a stacked Chandra image of the "normal" galaxies seen with Spitzer. The infrared emission for these young, massive galaxies is consistent with expectations for star formation. The Chandra image shows mainly low-energy X-ray emission at the center as expected. On the right, is a stacked Chandra image for galaxies with infrared emission exceeding the levels likely to be caused by star formation. These galaxies contain active galactic nuclei, or quasars, in their centers. These are luminous objects powered by the rapid growth of supermassive black holes. The obscured quasars show much higher levels of high-energy X-ray emission because the less energetic X-rays are mostly absorbed by gas.

In this image of the Hubble Ultra Deep Field, several objects are identified as the faintest, most compact galaxies ever observed in the distant universe. They are so far away that we see them as they looked less than one billion years after the Big Bang. Blazing with the brilliance of millions of stars, each of the newly discovered galaxies is a hundred to a thousand times smaller than our Milky Way Galaxy. The detection required joint observations between Hubble and NASA's Spitzer Space Telescope. Blue light seen by Hubble shows the presence of young stars. The absence of infrared light from Spitzer observations conclusively shows that these are truly young galaxies without an earlier generation of stars.

In this image of the Hubble Ultra Deep Field, several objects are identified as the faintest, most compact galaxies ever observed in the distant universe. They are so far away that we see them as they looked less than one billion years after the Big Bang. Blazing with the brilliance of millions of stars, each of the newly discovered galaxies is a hundred to a thousand times smaller than our Milky Way Galaxy. The bottom row of pictures shows several of these clumps (distance expressed in redshift value). Three of the galaxies appear to be slightly disrupted. Rather than being shaped like rounded blobs, they appear stretched into tadpole-like shapes. This is a sign that they may be interacting and merging with neighboring galaxies to form larger structures. The detection required joint observations between Hubble and NASA's Spitzer Space Telescope. Blue light seen by Hubble shows the presence of young stars. The absence of infrared light from Spitzer observations conclusively shows that these are truly young galaxies without an earlier generation of stars.

This artist's timeline chronicles the history of the universe, from its explosive beginning to its mature, present-day state. Our universe began in a tremendous explosion known as the Big Bang about 13.7 billion years ago (left side of strip). Observations by NASA's Cosmic Background Explorer and Wilkinson Anisotropy Microwave Probe revealed microwave light from this very early epoch, about 400,000 years after the Big Bang, providing strong evidence that our universe did blast into existence. Results from the Cosmic Background Explorer were honored with the 2006 Nobel Prize for Physics. A period of darkness ensued, until about a few hundred million years later, when the first objects flooded the universe with light. This first light is believed to have been captured in data from NASA's Spitzer Space Telescope. The light detected by Spitzer would have originated as visible and ultraviolet light, then stretched, or redshifted, to lower-energy infrared wavelengths during its long voyage to reach us across expanding space. The light detected by the Cosmic Background Explorer and the Wilkinson Anisotropy Microwave Probe from our very young universe traveled farther to reach us, and stretched to even lower-energy microwave wavelengths. Astronomers do not know if the very first objects were either stars or quasars. The first stars, called Population III stars (our star is a Population I star), were much bigger and brighter than any in our nearby universe, with masses about 1,000 times that of our sun. These stars first grouped together into mini-galaxies. By about a few billion years after the Big Bang, the mini-galaxies had merged to form mature galaxies, including spiral galaxies like our own Milky Way. The first quasars ultimately became the centers of powerful galaxies that are more common in the distant universe. NASA's Hubble Space Telescope has captured stunning pictures of earlier galaxies, as far back as ten billion light-years away.

The right panel is an image from NASA's Spitzer Space Telescope of stars and galaxies in the Ursa Major constellation. This infrared image covers a region of space so large that light would take up to 100 million years to travel across it. The left panel is the same image after stars, galaxies and other sources were masked out. The remaining background light is from a period of time when the universe was less than one billion years old, and most likely originated from the universe's very first groups of objects -- either huge stars or voracious black holes. Darker shades in the image on the left correspond to dimmer parts of the background glow, while yellow and white show the brightest light.

This image reveals a background glow of light from a period of time when the universe was less than one billion years old. This light most likely originated from the universe's very first groups of objects -- either huge stars or voracious black holes. The image from NASA's Spitzer Space Telescope shows a region of sky in the Ursa Major constellation. To create this image, stars, galaxies and other sources were masked out. This infrared image covers a region of space so large that light would take up to 100 million years to travel across it. Darker shades in the image on the left correspond to dimmer parts of the background glow, while yellow and white show the brightest light.

When one galaxy wont do the trick, perhaps 20,000 will do. In the blue image on the left, 24 micron images of over 20,000 faint, distant galaxies have been added together. None of these galaxies were detectable, alone, at longer wavelengths. The following green and red images show the resulting combined images at 70 microns and 160 microns, respectively, which result in a clear detection of the galaxies in the until-recently unresolved infrared background.

The top panel is an image from NASA's Spitzer Space Telescope of stars and galaxies in the constellation Draco, covering about 50 by 100 million light-years (6 to 12 arcminutes). This is an infrared image showing wavelengths of 3.6 microns, below what the human eye can detect. The bottom panel is the resulting image after all the stars, galaxies and artifacts were masked out. The remaining background has been enhanced to reveal a glow that is not attributed to galaxies or stars. This might be the glow of the first stars in the universe.