NASA held a press conference today to reveal some findings from two of its four CIBER (Cosmic Infrared Background ExpeRiment) sounding rocket missions. These CIBER missions launched from White Sands Missile Range in New Mexico in 2010 and 2012. Researchers at California Institute of Technology (Cal Tech) have now analyzed the data gathered by the CIBER mission’s 1.1-micron and 1.6-micron infrared cameras, and a new realization about the nature of our universe is beginning to dawn. CIBER detected a “surprising surplus of infrared light in the dark space between galaxies, a diffuse cosmic glow as bright as all known galaxies combined. The glow is thought to be from orphaned stars flung out of galaxies.” The Spitzer Space Telescope had previously detected some of this “background infrared” light, but scientists were split as to its origin. CIBER’s observations are helping to settle the debate.

James Bock, CIBER’s principal investigator, said, “[The amount of] light production cannot be explained by the known [star] population of the galaxy. Spitzer measurements set up this mystery: an infrared background glow. There were two ideas to explain this. One was that the very first galaxies born in the universe lit up and made this glow, and their remnants were responsible for this glow. The other was that faint stars flung from their galaxies “stray stars” are responsible for this light.”

Michael Zemkov, the study’s lead, is an astronomer at Cal Tech. He elaborated, “We think stars are being scattered out into space during galaxy collisions. While we have previously observed cases where stars are flung from galaxies in a tidal stream, our new measurement implies this process is widespread.”

This graphic illustrates how CIBER team measures a diffuse glow of infrared light filling the spaces between galaxies.

CIBER captured wide-field pictures of the cosmic infrared background at two infrared wavelengths shorter than those seen by Spitzer. Zemkov explained, “We then masked out stars and galaxies which we know [from the images], and what’s left is the large scale fluctuations … we determine that the light is extragalactic by excluding known sources within the galaxy. The spectrum of this emission is very blue [which means it increases in brightness at shorter wavelengths]. First galaxies have trouble making short-wavelength emissions because of absorption present in the early universe. The model we favor based on these data is that stars are threaded throughout space, in between galaxies.”

“It is wonderfully exciting for such a small NASA rocket to make such a huge discovery,” said Mike Garcia, program scientist from NASA Headquarters. “Sounding rockets are an important element in our balanced toolbox of missions from small to large.”

A recent image from NASA’s Hubble Space Telescope of a cluster of galaxies shows the same type of star glow as seen by CIBER only at smaller scales.

The Sounding Rocket Program is about 40 years old, and NASA touts it as “one of the most robust, versatile, and cost-effective flight programs at NASA.” The sounding rockets travel a relatively slow parabolic arc, carrying a specific scientific instrument into space for just 5-20 minutes. It’s an ideal arrangement, both because the rockets can access areas of space too low to be studied using satellites, and because of the relatively low cost of these missions. Sounding rockets never go into orbit, so they don’t need boosters, nor telemetry and tracking coverage. In many cases, only the experiment itself is changed from one sounding rocket mission to the next; it’s the closest to a parts-bin rocket NASA has ever used. This offers opportunities and flexibility to all kinds of researchers, because a sounding rocket mission can be designed, built and launched in as little a three months.

Karoline Gilbert, an assistant astronomer at Space Telescope Science Institute summarized, “The blue glow [see graphic, left] is halo stars, stars between galaxies, [and we now know] they provide about 10% of the total light starlight in the universe. Today’s results shed new light on how our universe is structured right now, and how it formed.”

NASA said in a press release after the press conference, “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 stripping of stars happened over cosmic history.”


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