Starship Asterisk*

I wouldn't think that the medium between galaxies would be so dense that such a thing could happen.

Guest wrote: I wouldn't think that the medium between galaxies would be so dense that such a thing could happen.

Click to play embedded YouTube video.

Hubblecast 72: Clues to a cosmic crime
HubbleESA

Uploaded on 4 Mar 2014
The newest episode of the Hubblecast showcases striking new observations of a spiral galaxy moving through the heart of a galaxy cluster named Abell 3627. This cluster is violently ripping the spiral's entrails out into space, leaving bright blue streaks as telltale clues to this cosmic crime.

Guest wrote:

I wouldn't think that the medium between galaxies would be so dense that such a thing could happen.

Could it be, that the dark matter is only this unsuspected intergalactic material?

APODFORIST wrote:That's really an awesome picture!

How long the Galaxy needed for drifting the distance shown on the picture?

Guest wrote:Could it be, that the dark matter is only this unsuspected intergalactic material?

Guest wrote:And does this mean that the intergalactical medium isn't expanding as the rest of the universe?

Isaak Blechman wrote:1. what is the real speed of the Galaxy through the cluster, may by 50 km/sec which is nothing? and it does'nt produce high pressure. 7000 km/sec is Hubble speed !

Guest wrote:OK... so what accelerated an entire galaxy to that velocity relative to the rest of the universe? And without destroying it? And how long ago did that happen given its relative velocity and the amount of matter being stripped away at the (apparent) current rate? Is there some supremely massive object or equally fast moving object (galaxy?) now heading in an opposite direction (relative to the universe) to counter this apparent imparted energy? Again, how do you accelerate an entire galaxy without destroying it? :?: :?: :?:

Chris Peterson wrote:

Guest wrote:OK... so what accelerated an entire galaxy to that velocity relative to the rest of the universe? And without destroying it? And how long ago did that happen given its relative velocity and the amount of matter being stripped away at the (apparent) current rate? Is there some supremely massive object or equally fast moving object (galaxy?) now heading in an opposite direction (relative to the universe) to counter this apparent imparted energy? Again, how do you accelerate an entire galaxy without destroying it?

It's only a moderately high velocity with respect to its local surroundings (not the rest of the Universe). It probably formed from material traveling that velocity- either due to primordial interactions, or primordial statistical variation. I don't think it's out of the question that it might have been ejected from a cluster due to gravitational perturbations, either.

Guest wrote:If the building blocks of that galaxy were ejected material from some other 'structure', then the other 'structure' must be imparted with opposite velocity vector components (subject to mass).

Chris Peterson wrote:
That 2000 km/s relative motion between gas clouds is certainly enough to reduce the collision interval between particles at mean free distances of tens of kilometers sufficiently to create shock fronts.

http://en.wikipedia.org/wiki/Shock_waves_in_astrophysics wrote:
<<A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium (solid, liquid, gas or plasma). Shock waves are characterized by an abrupt, nearly discontinuous change in the characteristics of the medium. Across a shock there is always an extremely rapid rise in pressure, temperature and density of the flow. A shock wave travels through most media at a higher speed than an ordinary wave [and] is treated as a discontinuity where entropy increases over a nearly infinitesimal region.

Shock waves are common in astrophysical environments:

• The bow shock of a solar system (the existence of our solar system's bow shock has been disputed recently).
  Supernova remnants driving a shock through the interstellar medium (ISM).
  Shocks traveling through a massive star as it explodes in a core collapse supernova.
  Shocks in interstellar gas, caused by a collision between molecular clouds or by a gravitational collapse of a cloud.
  Accretion shocks at the edge of galaxy clusters.

Because of the low ambient density, most astronomical shocks are collisionless. This means that the shocks are not formed by two-body Coulomb collisions, since the mean free path for these collisions is too large, often exceeding the size of the system. It is widely accepted that the mechanism driving these shocks consists of plasma instabilities, that operate on the scale of plasma skin depth(; i.e., ,) which is typically much shorter than the mean free path(; i.e., ).

It is known that collisionless shocks are associated with extremely high energy particles, although it has not been definitively established if the high energy photons observed are emitted by protons, electrons or both. The energetic particles are in general believed to be accelerated by the Fermi acceleration mechanism. It is usually agreed that shocks caused by supernova remnants expanding in the interstellar medium accelerate the cosmic rays measured above the Earth's atmosphere.

Shock waves in stellar environments, such as shocks inside a core collapse supernova explosion often become radiation mediated shocks. Such shocks are formed by photons colliding with the electrons of the matter, and the downstream of these shocks is dominated by radiation energy density rather than thermal energy of matter.

An important type of astrophysical shock is the relativistic shock, in which the shock velocity is a non-negligible fraction of the speed of light. These shocks are unique to astrophysical environments, and can be either collisionless or radiation mediated. Relativistic shocks are theoretically expected in gamma ray bursts, active galactic nucleus jets and in some types of supernova explosions.>>

Chris Peterson wrote:

Guest wrote:If the building blocks of that galaxy were ejected material from some other 'structure', then the other 'structure' must be imparted with opposite velocity vector components (subject to mass).

No, it is momentum that is conserved, not velocity. And if the galaxy was ejected from another cluster, it was by a conversion of orbital angular momentum to linear momentum. No reason we should expect to detect the parent region.