Cosmic Castaways’ Orphan Stars Shine in New Numbers

By on November 14, 2014 in

New research is occurring on up to half of the stars in the known universe, discovered to be drifting outside the safe havens of their home galaxies in unexpected numbers by a new study.

CIBER, or the “Cosmic Infrared Background Experiment,” is a set of telescopes launched into space to briefly study the “cosmic glow” emitted by what scientists had previously thought to be the light of the Universe’s first, primordial galaxies. During Astrophysicist Michael Zemcov and his team’s observation flights of CIBER during 2010 and 2012, however, they found scores of abandoned stars, shining into empty space in far greater quantities than previously thought.

This cosmic glow is actually called “extragalactic background light,” the sum of all light emitted by stars throughout our Universe’s history. Scientists studying this light discovered small fluctuations throughout that they thought may have been hints of the first galaxies in our universe, but what they found was actually something quite different.

CIBER was created to study the infrared light spectrum, and search for these light fluctuations or hints. Upon closer study of the data returned, however, Zemcov and his team discovered that the fluctuations were far too young and blue to have come from the earliest galaxies—light from them would have been redshifted all the way into the infrared spectrum by the Universe’s expansion. This light had to have come from somewhere else; somewhere like a patch of space, dark and empty but for a lonely star, ejected from its home galaxy.

The planetarium show Cosmic Castaways discusses the process of these star ejections in detail, but the basic premise is that when galaxies collide, they will often fling their “tails” away when their gravity cannot retain them post-collision. These tails slowly dissipate, leaving orphaned stars strewn throughout empty space.

There were far larger quantities of this background light than could be produced by just a few of these far-flung stars, leading Zemcov and his team to believe that as many as half of the Universe’s stars could be among those floating alone in the black, tossed away by their host galaxies.

“These stars produce as much background light as the galaxies themselves…” said CIBER team member Jamie Bock. “…This is telling us that stars are torn from their galaxies more often than previously thought…that’s really exciting.”

To learn more about these wandering stars, visit Science on The Half-Sphere and watch our “Cosmic Castaways” planetarium show.

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