It’s hard enough to figure out what dark energy and dark matter are, a task that will occupy physicists for a long time to come. But even if we confine ourselves to ‘normal’ or ‘baryonic’ matter (accounting only for some four or five percent of the universe), we’re still left with a problem. Baryons are heavy subatomic particles like protons and neutrons that experience the strong nuclear force, and the problem is that even these relatively familiar particles are only partially accounted for.
So where is the missing baryonic matter? The answer may lie in a thin haze of hot, low-density gas that connects galactic clusters. Call it WHIM, for warm-hot intergalactic medium. Dutch and German scientists now think they have uncovered a filament of such gas that connects the clusters Abell 222 and Abell 223. The properties of the gas, visible primarily in the far ultraviolet and X-ray bands, fit with simulations in terms of density and temperature. The scientists used the XMM-Newton X-ray observatory to identify the hitherto unobserved filament.
Image: Composite optical and X-ray image of galaxy clusters Abell 222 and Abell 223. The cluster pair is connected by a filament permeated by hot X-ray emitting gas. The optical image was obtained by SuprimeCam at the Subaru telescope, the X-ray image showing the distribution of the diffuse hot gas (yellow to red) was obtained by XMM-Newton. Credits: ESA/ XMM-Newton/ EPIC/ ESO (J. Dietrich)/ SRON (N. Werner)/ MPE (A. Finoguenov).
Norbert Werner (SRON Netherlands Institute for Space Research), who led this work, thinks the team is seeing at least some of the missing baryonic matter. Says Werner, “The hot gas that we see in this bridge or filament is probably the hottest and densest part of the diffuse gas in the cosmic web…”
That last phrase deserves explanation. I’m working through the paper, which likens the structure of the universe to such a web-like structure, with galactic clusters, the largest objects in the universe, congregating at the web’s densest nodes. Let me quote the scientists on this:
According to the standard theory of structure formation, the spatial distribution of matter in the Universe evolved from small perturbations in the primordial density field into a complex structure of sheets and filaments with clusters of galaxies at the intersections of this filamentary structure. The filaments have been identified in optical surveys of galaxies…, but the dominant fraction of their baryons is probably in the form of a low density warm-hot gas emitting predominantly soft X-rays.
Sheets and filaments, with the things we see clustering in the web’s threads and knots. Thirty to forty percent of the baryonic matter in the universe ought to reside in filaments connecting galactic clusters, according to a variety of simulations, but this seems to be the first unambiguous detection (although other candidates have been put forward). And while the observed filament closely tracks at least one previous simulation, we still haven’t seen the largest part of the missing matter:
…according to the simulations… the dominant fraction of the WHIM resides in a lower temperature and density phase, the existence of which still remains to be proven observationally. The detection of the dominant fraction of the WHIM will only be possible with dedicated future instrumentation…
In other words, we’re going to need a more advanced space-based observatory to extend such difficult work, this particular filament being detectable largely because it is along the line of sight from Earth, thus concentrating its emission in a small region of sky. Understanding how matter is distributed in these structures will help us better piece together this web-like structure and the place of baryons within it.
The paper is Werner, et al., “Detection of hot gas in the filament connecting the clusters of galaxies Abell 222 and Abell 223,” Astronomy & Astrophysics Letters, Volume 482-3 (May, 2008), p. L29 (abstract).
Why is it a low density warm hot GAS emitting soft X-Rays rather than a low density plasma?
The reason I ask is filamentary structures can have very different explanations in plasma vs. gas.
Hi Folks;
It is interesting to note that the deternination of the filamentary structures within WHIM may better enable us to utilize the intergalactic medium as an energy source and/or as a reaction mass for high gamma factor type craft such as any improved or yet to be developed interstellar ramjet concepts.
Mapping out the baryoic matter terrain within the visible universe may help us plan the best routes for far distant future intergalactic space missions to send humanity throughout the visible universe and beyond.
Thanks;
Jim
occam, I’ll see if I can get a comment from one of the MPE team on this.
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Publisher: University of Chicago Press
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occam, I just had a response to your question from Alexis Finoguenov as the Max Planck Institute for Extraterrestrial Physics. Here it is:
“We simply do not differentiate between hot gas and hot plasma. We use gas simply as a notation that laws of gasodynamics are applicable. Classical plasma experiments refer to densities much larger than ours but plasma effects are observed in our hot gas.”
Hi All
Baryonic dark matter is always worth investigating, especially if we one day build ram-scoops.
In SF it’s funny where ramscoops turn up – on the “Enterprise” and, curiously, on the “Liberator” from “Blake’s 7”, according to a recent retrospective piece in a TV pop-culture review of SF shows. Ramscoops also propelled Stanislaw Lem’s starship in his “anti-SETI” masterpiece, “Fiasko”.
Which leads me to ponder if we meet ETIs will we understand them? Carl Sagan believed ramscoop propelled starships would allow direct contact between ETIs – a reasonable possibility – but even then how much would we have in common? Worth a thought.
Hi Adam;
I could not agree with you more about the great potential for ram scoup powered starships. I would like to add that negative refraction index materials installed within the front of the ship could perhaps pull the ship in the direction of travel and opposite the direction of the incident CMBR highly dopplar blueshifted light. An elongatable cone in front the the ship could be lenthened to reflect the incomming CMBR for grazing incidence reflection for reduced drag. Additionally, the ship could be produced with as long as possible length relative to its cross-section for reduced drag inducing cross-section. Thermal collection mechanism could bleed off heat or be used to power electrodynamically powered propulsion systems wherein the heat of the incident CMBR could be recycled for increased net propulsion effeciency.
It would be wonderful if negative index of refraction materials could be developed which where operable over hard gamma ray frequencies. Perhaps some sort of dielectric neutronium with superconducting femtometer scale neutronium coils instilled in the dielectric in a 3-D matrix pattern might be the hard gamma ray analogue of the optical through microwave frequency negative refractive index materials currently the subject of research at certain universities and government labs. An intriguing idea, but Man oh Man, I would be hard pressed to see how even neutronium could hold up to blackbody hard gamma radiation flux. I feel somewhat confident on another level that our distant materials science folks might come up with such materials.
Even a gamma factor of 1,000 would help us sport about anywhere within the Milky Way galaxy during one long human working lifetime. Multigeneration high gamma space arks could enable us to go much farther. I will settle with simply starting with a gamma factor of 2 to 10 and constant comfortable accelleration and decelleration to sport about our local interstellar neighboorhood.
Thanks;
Your Friend Jim
Maybe thin filaments of gaseous baryonic matter link stars too, not only clusters or galaxies?
Food for ramscoops yes, but is it enough to overcome the drag coefficient?
Hi All
Jim, neutronium is unstable to neutron decay and only remains in existence in neutron stars because it is continuously regenerated. Take away the extreme density and gravity, and the neutronium will evaporate away explosively. A half-life of 15 minutes makes for some very energetic radioactive decay.
Quark matter is, potentially, stable but incredibly dense – and would probably collapse regular matter into quarkonium. If there is a stable higgsino, or chargino, then some sort of ultra-density material could be made from that. Hans Moravec’s old paper on such things is around on the web somewhere – and not much has changed in the ~ 25 years since he wrote it. We still have no samples of either higgsinium or monopolium, and still no known charginos or other supersymmetric beasties.
Lorentz contraction means that no reasonable taper-ratio will make much difference, though I am unsure about how the incoming particles look in the ship’s frame of reference. My CMB drag computations look suspect to me in hindsight – I think I threw in one too many powers of 2. But extreme gamma factors will mean extreme drag from the ambient proton medium – even at the critical mass density of the cosmos, which is much lower than the intragalactic mass density. Fields will mean drag too. I think intergalactic travel will always be measured in millennia of subjective time – extreme gamma factors will be rightly seen as fictional.
Hey Jim,
According to my short research on this observation I’ve come up with a hypothesis that might have space craft implications at some distant future time.
Occam’s Comic,
I propose a hypothesis that, along with probably many other possible scenarios, might explain the “bridge” and the related heating and the related soft X-rays.
Looking at the above picture of galaxies it appears that both galaxies are distended in a tear drop form in the direction from the photo of about 10:30.
In essence one galaxy seems to be “facing” the other. This might be due to a preferred magnetic field direction of which spiraling plasma particles move at high speeds from the “lower” galaxy to the upper galaxy. If this is the case, a spiraling high speed particle plasma flowing from bottom to top might create the observed cylindrical structure and greatly heat up neutral atomic and molecular hydrogen and other cloud matter. The interaction of the streaming plasma with more stationery clouds could produce soft X-rays.
Jim, Adam, Occam, Paul, dad, ljk,
This is seemingly a plasma-physics and cosmology playground finding, such as Eric Lerner and Co. (a different Werner than above) With such magnetic fields and a preferred direction from bottom to top, for instance, it would seem feasible (if this were the case) that someday we might be able to use this to our advantage not only for propulsion but for speed records. Similar alignments might be the future galactic highways for us, or maybe other space faring craft which are using it now, maybe fanciful but interesting speculation none the less.
What do you think?
your friend forrest
adam/jim, yes if we ever did meet eti’s how much could we possibly have in common!? but it would be great to have the opportunity to try to find out! also yes i see great promise for the concept of the ramscoup starship in fact i just went downstairs and got my old hardcover copy of cosmos by carl sagan that somebody gave me as a gift years ago.and on page 205 sure enough is a picture and schematic of just such a starship! sagan was great,just yesterday i watched episode 9 of cosmos( i have the whole series on dvd),and in it he talks about one of our favorite subjects traversable wormholes! lays it all out very clearly too i might ad and even surmises that even now advanced aliens may be using just such a “transit system”! cool stuff. thank you your friend george
Hi Adam and Forrest;
Adam, thanks for the correction in the calculation of electromagnetic drag and the insights on the unstable nature of neutronium on the scale of the size a space craft. I had not previously realised that pure neutronium would be unstables at ordinary pressures and gravity.
Perhaps nuetronium could somehow be stabilized when combined with other particles such as pions, mesons, or God knows what else as long as the neutronium would be largely electrically neutral so that it would not blast away in a coulombic force explosion.
One conceivable exception to the ion, hydrogen, and helium drag problem would be to simply absorb the kinetic energy of particle impact and then reradiate the energy in the form of thrust. Another bazaar idea that I am hard pressed to see how would work would be to simply use a matter wave based negative index of refraction like material that would somehow be pulled in the direction of the incident proton or ions and atoms as a matter wave analogue to electromagnetic negative index of refraction materials. Perhaps this would require an energy field instead of solid material in a reverse analogue sense to the fact that negative index of refraction materials for the pure energy of photons are solid material artifacts.
Forrest;
That is a very interesting idea. Utilizing magnetic or electric field gradients between galaxies or else where may by simmilar to using rivers on Earth to transport spacecraft or the jet stream to aid in commercial airline route effeciency. Given the vast volume of space, I get a feeling there must be someway to harness the vast electrodynamic energy available within it in the form of electric or magnetic fields.
Thanks;
Your Friend Jim
Hi George;
I still have my copy of cosmos. I must have read the entire book 3 to 4 times as it was just such a great work. I saw all of the episodes of the series also.
Every now and then I am tempted to dust off my old copy of cosmos and reread it if for no other reason than the fact that there is a certain nastalgia to that era in the 80s. There was much talk of deploying massive space based systems for defense against Soviet ICBMs, but unfortunately such talk was, well, defense related. But the fact that we were agressively considering fielding somewhat exotic space systems at least smacked of intense space development.
We need a replacement to all of the above in the form of a mandate to send mankind to the outer reaches of the solar system and beyond for peaceful, scientific, exploratory, and ethical purposes; in short just because space is there waiting to be explored.
Carl Sagan’s Grand Central Subway Station Concept for wormholes in His book Cosmos was particularly interesting. The idea of using huge natural macroscopic infrastructure for wormhole travel is cool.
Thanks;
Your Friend Jim
The Molecular Hydrogen Explorer H2EX
Authors: F. Boulanger, J.P. Maillard, P. Appleton, E. Falgarone, G. Lagache, B. Schulz, B.P. Wakker, A. Bressan, J. Cernicharo, L. Drissen, G. Helou, T. Henning, T.L. Lim, E.A. Valentijn, the H2EX collaboration
(Submitted on 20 May 2008)
Abstract: The Molecular Hydrogen Explorer, H2EX, was proposed in response to the ESA 2015 – 2025 Cosmic Vision Call as a medium class space mission with NASA and CSA participations. The mission, conceived to understand the formation of galaxies, stars and planets from molecular hydrogen, is designed to observe the first rotational lines of the H2 molecule (28.2, 17.0, 12.3 and 9.7 micron) over a wide field, and at high spectral resolution.
H2EX can provide an inventory of warm (> 100 K) molecular gas in a broad variety of objects, including nearby young star clusters, galactic molecular clouds, active galactic nuclei, local and distant galaxies. The rich array of molecular, atomic and ionic lines, as well as solid state features available in the 8 to 29 micron spectral range brings additional science dimensions to H2EX.
We present the optical and mechanical design of the H2EX payload based on an innovative Imaging Fourier Transform Spectrometer (IFTS) fed by a 1.2m telescope. The 20’x20′ field of view is imaged on two 1024×1024 Si:As detectors. The maximum resolution of 0.032 cm^-1 (FWHM) means a velocity resolution of 10 km s^-1 for the 0-0 S(3) line at 9.7 micron. This instrument offers the large field of view necessary to survey extended emission in the Galaxy and local Universe galaxies as well as to perform unbiased extragalactic and circumstellar disks surveys. The high spectral resolution makes H2EX uniquely suited to study the dynamics of H2 in all these environments.
The mission plan is made of seven wide-field spectro-imaging legacy programs, from the cosmic web to galactic young star clusters, within a nominal two years mission. The payload has been designed to re-use the Planck platform and passive cooling design.
Comments: Accepted for publication in Experimental Astronomy special issue on Cosmic Vision Proposals, 19 pages and 9 figures
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0805.3109v1 [astro-ph]
Submission history
From: Francois Boulanger [view email]
[v1] Tue, 20 May 2008 17:01:02 GMT (2805kb)
http://arxiv.org/abs/0805.3109