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Filling the Void

January 19, 2015

Our universe probably holds a hundred billion galaxies. And each galaxy contains anywhere from a few million stars to a trillion or more. Add it all up and that’s a whole lot of zeroes in the number of stars.

Yet that may be only half of the story. According to recent observations by a small space telescope, there may be as many stars between galaxies as in them.

A project known as CIBER launched a small infrared telescope several times. Each flight lasted just a few minutes, but the total time above the atmosphere allowed the telescope to measure much of the infrared light in the universe. Astronomers masked out the glow of galaxies, plus the infrared background of our own galaxy, the Milky Way.

When they ran the numbers, the astronomers found that a lot of infrared light was unaccounted for. This glow was spread fairly evenly across the sky.

According to the project scientists, the most likely explanation is that there are a lot of stars between the galaxies. The stars didn’t form out in these voids. Instead, they were stripped from their parent galaxies by interactions between galaxies. When galaxies get close to each other, the gravity of one can pull great streamers of stars from the other. Over time, the stars spread out, so they’re distributed fairly evenly between galaxies.

That may mean that there’s not a sharp “edge” to any galaxy. Instead, they all taper off as some of their stars spread into the intergalactic void.


Script by Damond Benningfield, Copyright 2014

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