NGC 1275- the stardust sound not heard

In 2003, astronomers detected the deepest note ever generated in the cosmos, a B♭, after 53 hours of Chandra observation. No human will actually hear the note, because it is 57 octaves below the keys in the middle of a piano. The sound waves appear to be generated by the inflation of bubbles of relativistic plasma by the central active galactic nucleus in NGC 1275 . Such plasmas may be created either by heating a gas to very high temperatures or by the impact of a high-energy particle beam. Since these temperatures are so high, most relativistic plasmas are small and brief, and are often the result of a relativistic beam impacting some target.  More mundanely, “relativistic plasma” might denote normal, cold plasma moving at a significant fraction of the speed of light relative to the observer.  Relativistic plasmas may result when two particle beams collide at speeds comparable to the speed of light, and in the cores of supernovae. Plasmas hot enough for particles other than electrons to be relativistic are even more rare, since other particles are more massive and thus require more energy to accelerate to a significant fraction of the speed of light.

The giant elliptical galaxy NGC 1275, at the center of the Perseus cluster, is surrounded by a well-known giant nebulosity of emission-line filaments, which are plausibly in excess of 108 years old3. The filaments are dragged out from the center of the galaxy by radio-emitting ‘bubbles’ rising buoyantly in the hot intracluster gas, before later falling back. They act as markers of the feedback process by which energy is transferred from the central massive black hole to the surrounding gas. The mechanism by which the filaments are stabilized against tidal shear and dissipation into the surrounding extremely hot gas has been unclear. Here we report observations that resolve the thread-like structures in the filaments. Some threads extend over 6 kpc, yet are only 70 pc wide. We conclude that magnetic fields in the threads, in pressure balance with the surrounding gas, stabilize the filaments, so allowing a large mass of cold gas to accumulate and delay star formation.

The existence of the filaments poses a problem. As they are much cooler than the surrounding intergalactic cloud, how have they persisted for perhaps 100 million years? Why haven’t they warmed, dissipated or collapsed to form stars? One possibility is that weak magnetic fields (about one-ten-thousandth the strength of Earth’s field) exert enough force on the threads to keep them together.

info found on web (several sources)including NASA, WIkipedia, and  http://mnras.oxfordjournals.org/content/367/2/433.full.pdf

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