On Sat, Jul 12, 2014 at 7:21 PM, Axil Axil <[email protected]> wrote:
> Regarding the title: 400 percent less light in universe than predicted > > This article and the title are not well written. > > The title should read that there are missing light *sources* not XUV > light. That is, the is more light produced than there are light sources. > > [Snip] > > “It’s as if you’re in a big, brightly lit room, but you look around and > see only a few 40-watt lightbulbs,” > > [EndSnip] > > There are less 40-watt light bulbs than would be expected for the amount > of XUV light produced. These bulbs are light sources. There is too much > light than the light sources can produce. > > > Oh, my mistake, so the subject header should say "400 percent more light in universe than predicted" Harry > On Sat, Jul 12, 2014 at 7:03 PM, H Veeder <[email protected]> wrote: > >> CU-Boulder instrument onboard Hubble reveals the universe is ‘missing’ >> light >> >> http://tinyurl.com/qzs4rjo >> >> July 9, 2014 • >> >> Something is amiss in the universe. There appears to be an enormous >> deficit of ultraviolet light in the cosmic budget. >> >> Observations made by the Cosmic Origins Spectrograph, a $70 million >> instrument designed by the University of Colorado Boulder and installed on >> the Hubble Space Telescope, have revealed that the universe is “missing” a >> large amount of light. >> >> “It’s as if you’re in a big, brightly lit room, but you look around and >> see only a few 40-watt lightbulbs,” said the Carnegie Institution for >> Science’s Juna Kollmeier, lead author of a new study on the missing light >> published in The Astrophysical Journal Letters. “Where is all that light >> coming from? It’s missing from our census.” >> >> The research team—which includes Benjamin Oppenheimer and Charles >> Danforth of CU-Boulder’s Center for Astrophysics and Space >> Astronomy—analyzed the tendrils of hydrogen that bridge the vast reaches of >> empty space between galaxies. When hydrogen atoms are struck by highly >> energetic ultraviolet light, they are transformed from electrically neutral >> atoms to charged ions. >> >> The astronomers were surprised when they found far more hydrogen ions >> than could be explained with the known ultraviolet light in the universe, >> which comes primarily from quasars. The difference is a stunning 400 >> percent. >> >> Strangely, this mismatch only appears in the nearby, relatively >> well-studied cosmos. When telescopes focus on galaxies billions of light >> years away—which shows astronomers what was happening when the universe was >> young—everything seems to add up. The fact that the accounting of light >> needed to ionize hydrogen works in the early universe but falls apart >> locally has scientists puzzled. >> >> The mismatch emerged from comparing supercomputer simulations of >> intergalactic gas to the most recent analysis of observations from the >> 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,” said CU-Boulder’s Oppenheimer. “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 type of light that is energetic enough to turn neutral hydrogen into >> hydrogen ions is called “ionizing photons” and is known to come from only >> two sources in the universe: quasars, which are 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 amount of light necessary >> to create the quantity of hydrogen ions measured by the research team. >> >> >> “If we count up the known sources of ultraviolet ionizing photons, we >> come up five times too short,” Oppenheimer said. “We are missing 80 percent >> of the ionizing photons, and the question is where are they coming from? >> The most fascinating possibility is that an exotic new source, not quasars >> or galaxies, is responsible for the missing photons.” >> >> 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. >> >> “The great thing about a 400 percent discrepancy is that you know >> something is really wrong,” said co-author David Weinberg of 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.” >> >> Other co-authors on the study are Francesco Haardt of the Università >> dell’Insubria, Romeel Davé of the University of the Western Cape, Mark >> Fardal of University of Massachusetts Amherst, Piero Madau of the >> University of California, Santa Cruz, Amanda Ford of the University of >> Arizona, Molly Peeples of the Space Telescope Science Institute, and Joseph >> McEwen of Ohio State University. >> >> The study was funded in part by NASA, the National Science Foundation and >> the Ahmanson Foundation. >> > >
