The Cosmic Light of Stray Stars Makes the Universe Brighter Than Expected

It turns out that the universe may be a far brighter place than expected. Using an experiment carried into space on a NASA suborbital rocket, astronomers have discovered a diffuse cosmic glow that appears to be more light than what's normally produced by known galaxies. The findings suggest that there may be undetected stars that permeate the "dark" spaces between galaxies.

In previous studies, NASA's Spitzer Space Telescope observed a splotchy pattern of infrared light called the cosmic infrared background. Yet the splotches were far larger than individual galaxies. Some argued that this light came from the very first galaxies to form and ignite stars after the Big Bang. Others, though, argued that the light originated from stars stripped from galaxies in more recent times.

In order to find out which was true, the researchers created the Cosmic Infrared Background Experiment (CIBER). The scientists had the idea of measuring galaxies' large-scale structure directly from maps.

The CIBER experiment itself consists of three instruments, including two spectrometers to determine the brightness of Zodiacal light, which is caused by dust in the solar system reflecting light from the sun, and to measure the cosmic infrared background directly. The measurements in this latest study were made with two wide-field cameras to search for fluctuations in two wavelengths of near infrared light.

In the end, the scientists found fluctuations and then removed local sources, such as the Milky Way, and known galaxies. What was left behind was a splotchy pattern that represented the fluctuations of the remaining infrared background light.

"Although we designed our experiment to search for emission from first stars and galaxies, that explanation doesn't fit our data very well," said Michael Zemcov, one of the researchers, in a news release. "The best interpretation is that we are seeing light from stars outside of galaxies but in the same dark matter hallows. The stars have been stripped from their parent galaxies by gravitational interactions-which we know happens from images of interacting galaxies-and flung out to large distances."

Currently, the scientists plan to see whether stray stars are indeed the source of the infrared cosmic glow or if there are other processes at work.

The findings are published in the journal Science.