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"All the Light in the Universe" --Is It Coming from an Exotic Unknown Source?





"It's as if you're in a big, brightly-lit room, but you look around and see only a few 40-watt light bulbs," noted Carnegie Institute's Juna Kollmeier. "Where is all that light coming from? It's missing from our census."

"The most exciting possibility is that the missing photons are coming from some exotic new source, not galaxies or quasars at all," said Neal Katz of the University of Massachusetts at Amherst. For example, the mysterious dark matter, which holds galaxies together but has never been seen directly, could itself decay and ultimately be responsible for this extra light. You know it's a crisis when you start seriously talking about decaying dark matter!"

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.

"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."

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.

The light in question consists of highly energetic ultraviolet photons that are able to convert electrically neutral hydrogen atoms into electrically charged ions. The two known sources for such ionizing photons are quasars—powered by hot gas falling onto supermassive black holes over a million times the mass of the sun—and the hottest young stars.

Observations indicate that the ionizing photons from young stars are almost always absorbed by gas in their host galaxy, so they never escape to affect intergalactic hydrogen. But the number of known quasars is far lower than needed to produce the required light.

"Either our accounting of the light from galaxies and quasars is very far off, or there's some other major source of ionizing photons that we've never recognized," Kollmeier said. "We are calling this missing light the photon underproduction crisis. But it's the astronomers who are in crisis—somehow or other, the universe is getting along just fine."

The mismatch emerged from comparing supercomputer simulations of intergalactic gas to the most recent analysis of observations from Hubble Space Telescope's Cosmic Origins Spectrograph. "The simulations fit the data beautifully in the early universe, and they fit the local data beautifully if we're allowed to assume that this extra light is really there," explained Ben Oppenheimer a co-author from the University of Colorado. "It's possible the simulations do not reflect reality, which by itself would be a surprise, because intergalactic hydrogen is the component of the Universe that we think we understand the best."

The image at the top of the page shows a type Ia supernovae that are brighter than whole galaxies and visible billions of light-years away. The Supernova Cosmology Project devised ways of finding Type Ia supernovae “on demand,” then measured the expansion of the universe with a precision that led to the discovery of dark energy.

The Daily Galaxy via the Carnegie Institution


Apparently not all light was created equally!

The active links in this article are the same color as the rest of the text, so that they can't be distinguished from the text except by accidentally mousing over them, eg., "The Astrophysical Journal Letters" in para 2.

Thanks for looking into this.

There is not enough mass, there isn't enough energy there isn't enough light. What is next? Perhaps there isn't enough poop on this planet to account for all the humans? Oh I cant wait for them to call for a dark light, or even a dark poop that exists.

the majority of light we see comes from our sun.

Manifestation of Dark Energy...

Black holes have expelled less energy the further you look into the past...

This is my best explanation. Black holes recycles the energy of expansion by bouncing it and keeping only the invariant mass of infalling particles.

Gee Michel, that's the first comment in this thread that makes any sense!

The source of light will be called "the spark".

That's not a picture of a supernovae.

That's a picture of galaxy with the focus on the bright bulge.

Apart from that there is NO second or brighter object or anything that could be described as a supernovae in the photo.

The photo is the Sombrero Galaxy.

There are so many unknown facts exist about the entire universe. We have to research about so many things to extract facts from which supports the reality. the number of known quasars is far lower than needed to produce the required light. Hope we will be able to solve this mystery as well gradually.

Well, we know dark matter exists. It seems reasonable to conclude that, over time, the second law of thermodynamics applies to dark matter as it does to everything else. That light might be the detectable product of dark matter decay is exciting.

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