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Universe's Missing Baryonic Mass Found

Posted December 14, 2015 9:32 AM by Bayes

One of the mysteries of astrophysics has been where all the baryons are. The sum of observed baryons falls short of what would be expected from Big Bang nucleosynthesis. For instance stars only account for 7% of the expected baryons.

Some scientists think they may have figured out where the baryons are hiding.

Universe's missing mass found in the cosmic web

The best estimate yet of how much mass is contained within the long, tenuous threads of hot gas thought to span the vast distances between galaxy clusters has been made by a team of astrophysicists in Europe. The researchers used the XMM-NewtonX-ray satellite to characterize three "filaments" of plasma extending from the galaxy cluster Abell 2744. Such filaments are believed to make up a cosmic web that permeates the universe, and the team says that the filaments are likely to contain much of the universe's ordinary or "baryonic" matter. Observations of the afterglow of the Big Bang known as the cosmic microwave background (CMB) suggest that protons, neutrons and other (three-quark) baryon particles only account for about 5% of the universe's energy density - the rest is believed to consist of enigmatic dark matter and dark energy. However, the combined mass of all of the stars within a radius of about a billion light-years from Earth only amounts to about 2.5% of the energy density within that region. Computer simulations predict that the missing baryons instead exist within low-density plasma filaments millions of light-years long. Indeed, in regions of the sky containing two galaxy clusters, smaller groups of galaxies can be seen tracing out a line between the clusters. These filaments are thought to permeate the universe, creating a "cosmic web" of galaxy clusters that is surrounded by an extremely low-density "void". The seeds for this web can be seen in the tiny fluctuations within the CMB; as the universe expanded, gravitational attraction caused slightly denser regions to accumulate mass, while less-dense regions lost mass.

Good target

To measure the baryonic mass of several filaments, Dominique Eckert of the University of Geneva in Switzerland and colleagues looked towards Abell 2744, which is a vast galaxy cluster with a mass 1000 trillion times that of the Sun lying about four billion light-years from Earth. Like other clusters, its mass consists of galaxies (about 2%), gas (around 15%) and dark matter (80-85%). It is a good target, say the researchers, because its composition suggests that it is located at the intersection of several filaments of the cosmic web. Although the gas in the filaments would be cooler than that in the cluster - at around several million degrees, as opposed to some 100 million degrees - it would still be hot enough to radiate at X-ray wavelengths. Eckert and his colleagues turned XMM-Newton towards Abell 2744 for 30 h last December, and studied the X-ray emission from the cluster and from a large volume of space around it. The researchers identified three structures of interest, each of which is several tens of millions of light-years long. A close match between the position of these structures and the location of galaxy concentrations away from the centre of the cluster allowed Eckert and colleagues to conclude that they had observed filaments of the cosmic web.

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#1

Re: Universe's Missing Baryonic Mass Found

12/14/2015 11:48 AM

So is this the "dark matter" or is this in addition to "dark matter"?

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#2
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Re: Universe's Missing Baryonic Mass Found

12/14/2015 11:51 AM

Hi Rixter,

No, not dark matter, just visible matter.

-R

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#11
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Re: Universe's Missing Baryonic Mass Found

12/15/2015 9:45 PM

"A baryon is a composite subatomic particle made up of three quarks (as distinct from mesons, which are composed of one quark and one antiquark). Baryons and mesons belong to the hadron family of particles, which are the quark-based particles."

"In astronomy and cosmology, baryonic dark matter is dark matter (matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter) composed of baryons, i.e. protons and neutrons and combinations of these, such as non-emitting ordinary atoms. Candidates for baryonic dark matter include non-luminous gas, Massive Astrophysical Compact Halo Objects (MACHOs: condensed objects such as black holes, neutron stars, white dwarfs, very faint stars, or non-luminous objects like planets), and brown dwarfs.

The total amount of baryonic dark matter can be inferred from Big Bang nucleosynthesis, and observations of the cosmic microwave background. Both indicate that the amount of baryonic dark matter is much smaller than the total amount of dark matter.

In the case of big bang nucleosynthesis, the problem is that large amounts of ordinary matter means a denser early universe, more efficient conversion of matter to helium-4 and less unburneddeuterium that can remain. If one assumes that all of the dark matter in the universe consists of baryons, then there is far too much deuterium in the universe. This could be resolved if there were some means of generating deuterium, but large efforts in the 1970s failed to come up with plausible mechanisms for this to occur. For instance, MACHOs, which include, for example, brown dwarfs (balls of hydrogen and helium with masses less than 0.08 M or 1.6×1029 kg), never begin nuclear fusion of hydrogen, but they do burn deuterium. Other possibilities that were examined include "Jupiters", which are similar to brown dwarfs but have masses 0.001 M (2×1027 kg) and do not burn anything, and white dwarfs.[1][2][clarification needed]"

https://en.wikipedia.org/wiki/Baryonic_dark_matter

  • Nonbaryonic dark matter

"Dark matter is a hypothetical kind of matter that cannot be seen with telescopes but accounts for most of the matter in the universe. The existence and properties of dark matter are inferred from its gravitational effects on visible matter, on radiation, and on the large-scale structure of the universe. Dark matter has not been detected directly, making it one of the greatest mysteries in modern astrophysics.

Dark matter neither emits nor absorbs light or any other electromagnetic radiation at any significant level. According to the Planck mission team, and based on the standard model of cosmology, the total mass-energy of the known universe contains 4.9% ordinary (baryonic) matter, 26.8% dark matter and 68.3% dark energy.[2][3] Thus, dark matter is estimated to constitute 84.5%[note 1] of the total matter in the universe, while dark energy plus dark matter constitute 95.1% of the total mass-energy content of the universe.[4][5][6]"

https://en.wikipedia.org/wiki/Dark_matter

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#3
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Re: Universe's Missing Baryonic Mass Found

12/14/2015 2:48 PM

@Rixter: No, baryonic matter is supposed to make up 5% of the critical energy density, but we so far could identify only half of that inside galactic clusters and filaments together. This new study may have found the other 2.5% in the form of hot gas in the filaments.

Dark matter involves another 25% of critical density, but we do not know what sort of matter it is.

-J

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Re: Universe's Missing Baryonic Mass Found

12/14/2015 6:05 PM
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#6
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Re: Universe's Missing Baryonic Mass Found

12/14/2015 10:50 PM

Solar: "I thought it was quark dust...."

AFAIK, no such dust or soups around today, except perhaps for fleeting moments inside the LHC.

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#10
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Re: Universe's Missing Baryonic Mass Found

12/15/2015 11:35 AM

Jorrie: I am somewhat disappointed. I had hoped for a long time (all of two minutes), that the dust that collects at the bottom of my TV screen after watching the Science Channel (How the Universe Works), etc., was comprised of quark dust, but alas it is entirely condensed matter, all hadronic.

The OP article was pretty good, and the informative link in Solar Eagle's post helped me get a better grip on the topic that is entirely fascinating. 2 trillion degrees is a far piece hotter than even a faulty toaster oven.

Thanks for the entertainment, gentlemen. Keep up the good work, and I hope they find the rest of the missing mass. It is critical that we do so, I suppose, before everything flies apart.

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#5

Re: Universe's Missing Baryonic Mass Found

12/14/2015 6:35 PM

Hmmm. Baryons you say? I think I have a few buckets of old ones in my shop some place.

Given the amount of stuff I have the odds are in my favor they're in there!

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#7

Re: Universe's Missing Baryonic Mass Found

12/15/2015 12:10 AM

Filaments have been discussed here before such as in my thread "Book Review: The Big bang Never Happened" and "Big Bang Theory Flawed" remarks by JohnJohn.

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#8

Re: Universe's Missing Baryonic Mass Found

12/15/2015 6:25 AM

We designed & made the XMM visible detector in the UK for Mullard on this mission, seems a long time ago now.

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#9

Re: Universe's Missing Baryonic Mass Found

12/15/2015 10:57 AM

Has anyone looked in the bottom of Margaret Burbidge's purse? I bet it's in there.

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#12

Re: Universe's Missing Baryonic Mass Found

12/15/2015 9:56 PM
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