The vast reaches of empty space between galaxies are bridged by tendrils of hydrogen and helium, which can be used as a precise “light meter.” In a recent study published in The Astrophysical Journal Letters, a team of scientists finds that the light from known populations of galaxies and quasars is not nearly enough to explain observations of intergalactic hydrogen. The difference is a stunning 400 percent.
“It’s as if you’re in a big, brightly-lit room, but you look around and see only a few 40-watt lightbulbs,” noted Carnegie’s Juna Kollmeier, lead author of the study. “Where is all that light coming from? It’s missing from our census.”
Strangely, this mismatch only appears in the nearby, relatively well-studied cosmos. When telescopes focus on galaxies billions of light years away (and therefore are viewing the universe billions of years in its past), everything seems to add up. The fact that this accounting works in the early universe but falls apart locally has scientists puzzled.
As problems go, it sounds like more fun than summer camp, actually.
“The great thing about a 400% discrepancy is that you know something is really wrong,” commented co-author David Weinberg of The Ohio State University. “We still don’t know for sure what it is, but at least one thing we thought we knew about the present day universe isn’t true.”
Let us be the first to know, okay?
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