The Hubble Space Telescope has captured a series of close-ups showing spectacularly bright infrared galaxies – as much as 10,000 times more luminous than our Milky Way – pumping out stars and surrounded by tangles of misshapen objects and exotic patterns of rings.

To capture the images of the rare, far-distant formations, scientists capitalized on gravitational lensing. In this cosmic magnifying glass effect, the powerful gravity of massive galaxies in the foreground magnifies the fainter light from galaxies in the background. Previous observations of the galaxies hinted that the phenomenon was at work. Hubble’s keen vision confirmed it.

“We have hit the jackpot of gravitational lenses,” said lead researcher James Lowenthal of Smith College in Northampton, Massachusetts. “These ultra-luminous, massive, starburst galaxies are very rare. Gravitational lensing magnifies them so that you can see small details that otherwise are unimaginable. We can see features as small as about 100 light-years or less across. We want to understand what’s powering these monsters, and gravitational lensing allows us to study them in greater detail.”

The galaxies are cauldrons of star-making activity, pumping out more than 10,000 new stars a year. The unusually rapid pace of star birth is occurring at the peak of the universe’s star-making boom more than 8 billion years ago.

Dust shrouds the galaxies, making them too faint to detect in visible light. In infrared light, however, they glow fiercely, shining with the light of 10 trillion to 100 trillion suns.

Only a few dozen of these galaxies exist in the universe. They reside in random, unusually dense regions of space where rapid star formation took place in the early universe.

“There are so many unknowns about star and galaxy formation,” Lowenthal said. “We need to understand the extreme cases, such as these galaxies, as well as the average cases, like our Milky Way, in order to have a complete story about how galaxy and star formation happen.”

One of the most tantalizing questions: What’s powering the prodigious birth of stars? The galaxies may be distant cousins of the ultra-luminous infrared galaxies (ULIRGS) seen in the nearby universe. ULIRGS’ star-making is stoked by the merger of two spiral galaxies.

It may also be possible that lots of gas, the material that makes stars, is flooding into the faraway galaxies. “Maybe gas is raining down on the galaxies, or they are fed by some sort of channel or conduit, which we have not figured out yet,” Lowenthal said.

Future telescopes, such as NASA’s James Webb Space Telescope, an infrared observatory set to launch in 2018, will measure the speed of the galaxies’ stars so that astronomers can calculate the mass of these ultra-luminous objects.

“The sky is covered with all kinds of galaxies, including those that shine in far-infrared light,” Lowenthal said. “What we’re seeing here is the tip of the iceberg: the very brightest of all.”

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