| | | | | | |
| | |||||
|
How an X-ray Telescope Detected Sound from a Black HoleWhat is sound? How can it be generated by a black hole? How can an X-ray telescope detect the sound?
Sound is generated when an object makes a disturbance in a medium. Examples include vibrations from our vocal chords, from a tuning fork or from a membrane in a stereo speaker. In the Perseus galaxy cluster, scientists believe that sound is generated in the following way: cavities or bubbles in the cluster gas are blown out by jets from a supermassive black hole (located at the center of the cluster). These cavities eventually push against the cluster gas like a piston, generating a pair of sound waves which travel away from the now slowly traveling cavities. [View the animation] How is the Chandra X-ray Observatory able to detect these sound waves?
Although the sound waves in the Perseus cluster are moving rapidly, distance to the cluster is so large (250 million light years) that the motion of the waves is undetectable from Earth. What type of sound is being generated by the black hole? If sound waves are produced at fixed, regular time intervals, then a tone, or note is created, similar to the production of musical notes with a tuning fork. The frequency (or pitch) of the note depends on the size of the tuning fork: a small tuning fork moves more rapidly, generating a closely spaced set of sound waves, corresponding to a high frequency note. A larger tuning fork moves more slowly generating more widely spaced pressure waves and a lower frequency note.
The sound waves provide a critical source of energy for keeping the cluster gas from cooling too much, preventing massive amounts of star formation. Scientists have calculated that the pitch and intensity of the sound from the black hole would have had to have been roughly constant for about 2.5 billion years to offset cooling from radiation. [Return to Perseus Cluster Press Kit] |
||||||||||||
Revised: August 29, 2006
|
||||||||
