Re: Star chime could reveal small black holes

On 13/09/2011 14:49, Yousuf Khan wrote:
On 09/12/2011 05:06 PM, Sam Wormley wrote:
Star chime could reveal small black holes

"In theory, black holes come in all sizes, not just the star- and
galaxy-scale objects that astronomers have already seen. In particular,
smaller “primordial” black holes might have formed from density
fluctuations in the first seconds after the big bang. In addition to
providing a window into the universe in its earliest moments, these
remnants could be the cold dark matter that makes up about a quarter of
its present mass.

"Previous observations rule out abundant black holes smaller than 10^-16
or larger than 10^-7 times the mass of the sun, but intermediate sizes
could still account for cold dark matter. In Physical Review Letters,
Michael Kesden at New York University and Shravan Hanasoge at Princeton
University, New Jersey, propose that these medium-sized black holes
could be detected when they pass through a star. Although the black hole
will hardly be affected, it will leave lingering acoustic vibrations in
the star, analogous to the ringing of a bell".


Stars are chiming for their own internal reasons all of the time. How do
they propose to discern the difference between one type of chime and

Try reading the abstract!

The hard part will be distinguishing this ringing from the ambient vibrations caused by turbulent fluid motion. But the researchers calculated that a black hole passing through a star like the sun excites modes with higher frequencies and larger spatial scales than turbulence does, making it easily noticeable.