Against the Grain: NASA Says Half of All Stars Are in Between Galaxies

NASA had announced a press conference for yesterday afternoon to reveal amazing findings that would ‘change how we look at galaxies.’  And they did just that, sort of.

Findings from the Cosmic Infrared Background Experiment (CIBER) reveal that there is a huge surplus of Infrared light present in the vast darkness that exists between Galaxies.  Infrared light is invisible to the human eye, but is emitted by most room temperature objects.  It fills the EM spectrum at wavelengths longer than visible light (See yesterday’s post for the EM spectrum).  This surplus of light is greater than what we would expect from galaxies alone.  It was also found that the Infrared light has a blue spectrum, meaning it gets brighter at shorter wavelengths.  This is evidence that the light comes from a huge population of stars hiding in the darkness between Galaxies.

We’ve known about the Cosmic Infrared Background (CIB) for over 40 years, its been seen by IRAS, ISO, COBE, and the Spitzer Space Telescope.  The debate about the CIB has been whether its origin was stars between Galaxies or the light from the youngest Galaxies at the edge of the visible Universe.  The CIBER evidence points to a stellar origin, as the light from young galaxies would give a spectrum redder than what was seen.

CIBER Rocket Launch. Credit: T. Arai/University of Tokyo

CIBER uses a series of suborbital sounding rockets, much smaller than rockets used to carry satellites to space.  The goal of the rocket is to get above the atmosphere, as any ground-based observations in Infrared light are obscured by the warm air in the lower atmosphere. Once the rocket reaches the upper atmosphere, it can snap pictures for about 7 minutes before transmitting the data back to Earth.  Scientists removed the light from Stars and Galaxies in the images and removed any light coming from other sources such as the Milky Way Galaxy.  What remains is a map of all the CIB light, which can be measured by the team.

Credit: NASA/ JPL-Caltech
Credit: NASA / JPL-Caltech

James Bock, principal investigator of the CIBER project, summarized the results. “The simplest explanation, which best explains the measurements, is that many stars have been ripped from their galactic birthplace, and that the stripped stars emit on average about as much light as the galaxies themselves.” Future work by the CIBER team will look to verify this result by determining how many stars exist between galaxies, and how much of their light contributes to the observed CIB.

Although this doesn’t change the way I think about Galaxies, it does change the way I think about the vast darkness between Galaxies.  Maybe it isn’t totally dark after all.  Imagine Earth was a planet orbiting one of these stars.  The night sky would be nearly devoid of stars, as there probably aren’t many stars close enough to be seen with organic eyes.  Although there could be Billions of stars in the space between Galaxies, this space so vast that the distance between the neighbouring stars would be large enough to consider them ‘lonely wanderers.’


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