Space Telescope Science
Astronomers were fascinated in the 1980s with the discovery of nearby dust-enshrouded galaxies that glowed thousands of times brighter than our Milky Way galaxy in infrared light. Dubbed ultra-luminous infrared galaxies, they were star-making factories, churning out a prodigious amount of stars every year. What wasn't initially clear was what powered these giant infrared light bulbs. Observations by the Hubble Space Telescope helped astronomers confirm the source of the galaxies' light output. Many of them reside within "nests" of galaxies engaged in multiple pile-ups of three, four or even five galaxies. The dust is produced by the firestorm of star birth, which glows fiercely in infrared light.
Now Hubble is illuminating the bright galaxies' distant dust-enshrouded cousins. Boosted by natural magnifying lenses in space, Hubble has captured unique close-up views of the universe's brightest infrared galaxies. The galaxies are ablaze with runaway star formation, pumping out more than 10,000 new stars a year. This unusually rapid star birth is occurring at the peak of the universe's star-making boom more than 8 billion years ago. The star-birth frenzy creates lots of dust, which enshrouds the galaxies, making them too faint to detect in visible light. But they glow fiercely in infrared light, shining with the brilliance of 10 trillion to 100 trillion suns.
The galaxy images, magnified through a phenomenon called gravitational lensing, reveal a tangled web of misshapen objects punctuated by exotic patterns such as rings and arcs. The odd shapes are due largely to the foreground lensing galaxies' powerful gravity distorting the images of the background galaxies. Two possibilities for the star-making frenzy are galaxy collisions or gas spilling into the galaxies.