For billions of years, galactic train wrecks have scattered stars across the cosmos. Alone in space, the celestial orphans only dimly light their drift through the blackness. Now, after detecting the faint flickers, astrophysicists believe they have found that cosmic collisions may have left as many as half of all stars floating without a galaxy.
“The merging of galaxies is a messy process,” said Michael Zemcov, an astrophysicist from Caltech and lead author on the study published Thursday in Science. “Some of the stars mash together and form bigger galaxies, but some of them get tossed out completely and flung over very large distances.”
Many of the reclusive stars form dim halos around the galaxies in which they used to reside. Although astronomers previously knew about these halos, they were unsure of how many there were, because the light that singular stars emit gets drowned out by their much brighter neighboring galaxies.
As a part of their research into ancient galaxies, Zemcov and his team of scientists from the U.S., Japan, and Korea, launched a rocket equipped with a built-in telescope to take an enormous picture of space. The experiment, called Cosmic Infrared Background Experiment, or CIBER, had a field of view that was 20 times larger than the surface of the moon, according to Zemcov. It offered the team a single image of millions of galaxies.