Sounding Rocket Sheds New Light On Surprising Cosmic Glow

Chuck Bednar for redOrbit.com – Your Universe Online
An experiment designed by astronomers at the California Institute of Technology (Caltech) and carried into space on a NASA sounding rocket has detected a diffuse cosmic glow that appears to represent more infrared light than is produced by the known galaxies in the universe, officials at the US space agency announced on Thursday.
The researchers detected the surplus of infrared light in the dark space between galaxies, and they believe that the glow is from orphaned stars that had been ejected from galaxies. Furthermore, the Caltech researchers, who reported their findings in the journal Science, could redefine the scientific definition of a galaxy to indicate that they do not have set boundaries but are vast and interconnected.
The observations were obtained from NASA’s Cosmic Infrared Background Experiment (CIBER) rocket, and according to the agency, they are helping to settle an ongoing debate about whether this background infrared light (which had previously been detected by the Spitzer Space Telescope) originated from streams of far-flung stars that are too distant to be observed individually, or if it comes from the first galaxies to form in the universe.
[ Watch the Video: NASA Rocket Experiment Finds Flood Of Cosmic Light ]
In the new study, Caltech physics professor Jamie Bock, senior postdoctoral fellow Michael Zemcov and their colleagues report that the best explanation is that the cosmic light came from stars that had been ejected from their parent galaxies and flung out into space as those galaxies collided and merged with other galaxies. These previously undetected stars could actually reside in what was thought to be dark spaces between galaxies, they added.
“We think stars are being scattered out into space during galaxy collisions,” Zemcov, lead author of the study and an astronomer at NASA’s Jet Propulsion Laboratory in Pasadena, California, said in a statement. “While we have previously observed cases where stars are flung from galaxies in a tidal stream, our new measurement implies this process is widespread.”

Image Above: This graphic illustrates how CIBER team measures a diffuse glow of infrared light filling the spaces between galaxies. Credit: NASA/JPL-Caltech
Bock, who is the principal investigator on the CIBER project (which originated at Caltech) as well as a senior research scientist at JPL, added that even though the stars cannot be seen individually, the total combined light that they produce is “about equal to the background light we get from counting up individual galaxies.”
Previously, Spitzer observed a patchy pattern of infrared light known as the cosmic infrared background. However, the space telescope only looks at the universe in longer wavelengths. Using suborbital sounding rockets, CIBER was able to capture wide-field pictures of the cosmic infrared background at two infrared wavelengths shorter than Spitzer. Due to the glow of Earth’s atmosphere at those wavelengths, the measurements had to be done from space.
During the CIBER flights, the cameras used for the experiment were launched into space, capturing images for approximately seven minutes before transmitting the data back to Earth. Once the researchers received that data, they masked out galaxies and bright stars, then eliminated light coming from any other local sources. Ultimately, they wound up with a map showing fluctuations in the remaining infrared background light, according to NASA.
The splotches that remained were far larger than individual galaxies, and the brightness of their fluctuations allowed the study authors to measure the total amount of background light. To their surprise, their maps revealed a tremendous excess of light beyond that produced by galaxies. Furthermore, the CIBER data found that the infrared background light has a blue spectrum, meaning that it becomes brighter when viewed at shorter wavelengths.
“This is evidence the light comes from a previously undetected population of stars between galaxies. Light from the first galaxies would give a spectrum of colors that is redder than what was seen,” NASA explained. “Future experiments can test whether stray stars are indeed the source of the infrared cosmic glow. If the stars were tossed out from their parent galaxies, they should still be located in the same vicinity.”
“The CIBER team is working on better measurements using more infrared colors to learn how the stripping of stars happened over cosmic history,” the agency added. Researchers from the Los Alamos National Laboratory, the Japan Aerospace Exploration Agency (JAXA), the Seoul National University, the Korea Astronomy and Space Science Institute (KASI), and other US and international universities also took part in the study.
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