October 30, 2003

Blackhole tone

Went to see GB. Before he got to show me some of his simulations he told me about modes of vibration in stars. Caused by fluctuations in the equilibrium between gravity pulling inwards and pressure pulling outwards they vibrate in different planes - modes. So they must make a sound. Whether one can hear it or not is another matter. So there's something to follow up, helio seismology, study of pulsations of the sun. He explained how the black hole made a sound. I'd been wondering how you could have sound in a vacuum but of course it's not. The black hole is in the centre of  the Perseus cluster, a vast cloud of hot hot gas (density, a few 100 atoms per cubic meter, ie not very dense). Hit the cluster and it will "ring". The black hole does the hitting by spewing out plumes of gas. We worked out that the length of time for one cycle of the low low B flat is around 20 million years !

Watched some beautiful simulations - birth of a star in the early universe - clouds of  hydgoren and helium in which the denser areas exert a gravitational pull and gather more gas until they start to collapse into each other forming bigger and bigger clumps until a star is born. In the simulation the new born star looked very fragile and waif like.

Looked at some other simulations of clusters.

KC talked to me about theology and astrophysics and then about pulsars. I never realised how small they were, that you could fit one within the ring road of Oxford. A super dense spinning ball of iron humming above the spires. I'm wondering whether it's possible to make one. Is it the density or just the magnetised spinning iron bit thats crucial ?

Posted by Jem Finer at October 30, 2003 10:44 PM