[Sherman Logan]

It is thought that these hot intergalactic hazes were created from material that did not fall into galaxies when they first formed more than 13 billion years ago.

Stupid question time.

Why haven't these hot gases cooled off in the last few billion years, if they're in intergalactic space far from energy sources?

[Pontiac]

The missing part of this matter was thought to be a hot, ultra-thin gas haze of very low density between larger structures. Its hellacious temperature means that it only emits far-ultraviolet and X-ray radiation.

A similar baryonic haze, 150 times hotter than the sun's surface, was indirectly detected surrounding the Milky Way

Puzzling

What keeps this ultra-thin gas haze of very low density so hot for 13 billion years?

One would think that only fusion could do this. But Physics as I understand it would require enormous pressures to sustain fusion reaction. Such pressures do not exist in the vacuum of space.

There must be physics at work here that we do not understand. Once we do I think our energy crisis is over.

[grey_whiskers]

Why haven't these hot gases cooled off in the last few billion years, if they're in intergalactic space far from energy sources?

First describe the definition of temperature and the ordinary mechanisms of cooling.

Then the answer may become clearer.

Hint: T, R, and V.

Photon emission too.

Cheers!

[dr_lew]

Why haven't these hot gases cooled off in the last few billion years, if they're in intergalactic space far from energy sources?

Found this in an abstract from a 2001 paper, Baryons in the Warm-Hot Intergalactic Medium :

"The evolution of the WHIM is primarily driven by shock heating from gravitational perturbations breaking on mildly nonlinear, nonequilibrium structures such as filaments. Supernova feedback energy and radiative cooling play lesser roles in its evolution."

Based on the wikipedia entry for Intergalactic Space, I think the shock heating refers to the particles "falling" into these zones and gaining gravitational energy. This energy becomes thermal as they interact. This is a very thin plasma, and the interactions occur when the charged particles pass very near each other and emit "brehmstrahlung" X-rays . Brehmstrahlung means "braking radiation" and is a result of the electrostatic interaction of the particles.

Anyway, they're saying that the radiation is weak enough so that it is not a significant drain of the energy of the WHIM. The abstract of the article from the news link says the thermal energy is of the same order as the detected X-rays, so this means that the interaction time per particle must be much greater than 1 billion years, I believe.

Heaven's net casts wide. Though its meshes are coarse, nothing slips through. - LAO-TSU

( on the fly-leaf of Timothy Ferris's GALAXIES )