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Half of Stars Could Exist Outside Galaxies

Antennae galaxies

Image credit: Antennae galaxies (NGC 4038 & 4039) Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration

Stars and planets are usually thought to exist nicely within galaxies. We are sure that occasionally there are events that push a star outside of the galaxy and it was destined to go around the universe itself, which happened rarely based on previous assumption.

However, the latest research led by Michael Zemcov of Caltech, has showed that rogue stars could take almost fifty percent of all the stars in the universe. Their study was published recently in Science.

By using a series of four suborbital rockets called Cosmic Infrared Background Experiment (CIBER), scientists had collected the data from the period of 2009 to 2013. Jamie Bock, the principal investigator of Jet Propulsion Laboratory was the project leader. With the help of three instruments, CIBER succeeded in making measurement of near infrared wavelengths in the cosmic infrared background.

In the end, they found that the black, empty area between galaxies was not really as dark or vacant as they previously thought. In fact, the region between galaxies was littered with rogue stars. The total brightness of such stars accumulated up to about the same as what could be observed in galaxies. As the stars were very far away, they could be not seen as individual. However they seemed to make a remarkable impact when they were observed all together.

According to Zemcov, although it was amazing action to measure such huge fluctuations, but his team had already been engaged in many tests, which demonstrated that the results were actually reliable.

Zemcov’s team was following closely the previous observations made by Spitzer Space Telescope of NASA. Such observations showed unusual patterns in the cosmic infrared background, which were too big to be attributed to galaxies.

However, by collecting data via longer infrared wavelengths, Spitzer failed to resolve what they were. Therefore, scientists developed CIBER as a necessary tool for collecting the related data more thoroughly instead of using present telescopes, such as ESA’s Herschel. At the beginning, the team made the speculation that this light was discharged from some of the oldest galaxies and black holes in the universe, but in fact, the redshift of light showed that it could not be that old because of its shining brightness.

As Zemcov said, CIBER did present a couple of important facts. The fluctuations appeared too bright to come from the first galaxies. When people wanted burn a big amount of hydrogen into helium so as to have that much light, then they should hide the evidence, because scientists failed to observe enough heavy elements which were made by stellar nucleosynthesis [fusion of heavy elements in the core of stars], so it meant  these elements would have to disappear into black holes.

Although the data appeared to completely confirm the idea of an intergalactic sea of rogue stars, it was still far from being a slam dunk. The light’s color was not as blue as it should be to best explain it in the case of solitary stars. In addition, the quantity of light that was being produced between galaxies was so great that they could be ignored. Scientists were intended to be engaged in further study to identify whether these findings were accurate.

For the time being, the team is planning CIBER2 to trace these observations. It is hoped that the second generation would be able to expand the spectrum of IR light to be collected.

Source: Caltech, Science

Journal reference: Zemcov, Michael, et al. “On the origin of near-infrared extragalactic background light anisotropy.” Science 346.6210 (2014): 732-735.