While time travel is seemingly impossible, we can actually look back in time with our telescopes to learn about the conditions of our universe in times past. The Spitzer Space Telescope has found some very dim and distant galaxies located at the edge of our universe that have never been seen before. Approximately 12.5 billion light-years away from Earth, we’re seeing these galaxies as when our universe was just one billion years old. With Spitzer's infrared capability, astronomers have been able to take infrared portraits and even "weigh" many of these early galaxies. "Understanding the mass and chemical makeup of the universe's first galaxies and then taking snapshots of galaxies at different ages, gives us a better idea of how gas, dust and metals– the material that went into making our Sun, solar system, and Earth –has changed throughout the Universe's history," said Spitzer scientist Dr. Ranga Ram Chary.

Unlike the galaxies of today, Chary says that galaxies living in the one billion year old universe were much more pristine. They were comprised primarily of hydrogen and helium gas and contained less than 10% of the heavier elements we see in the local Universe today, and even on Earth. Astronomers have found these distant galaxies were cosmic "lightweights", or not very massive compared to mature galaxies we see nearby.

"A few billion years after the big bang, 90 percent of the stars being born were occurring in these types of faint galaxies. By identifying this population, we hope to gain insights into the environments where the universe's first stars formed," said Chary.