Origin of the Universe, Class 9

Origin of the Universe, Class 9 Origin of the Universe - Class 9

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Presentation by Gretta Thorn and Julie Sargeant: "Origin of life"
Comment: see the review of The Life of the Cosmos, by Lee Smolin.

Review by Thomas Nelson

Black hole collisions and growth. Spinning black holes. Hawking radiation.
Jets, searchlights, x-ray bursts.
Detecting black holes: tight orbits, X-ray emissions, gamma-ray bursts, gravitational lensing.

Black Holes from tight orbits

(Adapted from http://www.astro.soton.ac.uk/PH308/AGN/BH_masses.html)

By measuring the motions of material very close to the centers of galaxies, and assuming that they follow approximately circular orbits, it is possible to obtain direct measurement for the masses in these regions, based on the formula M = rv²/G, where:

v is the velocity at which material is observed to be orbiting
r is the radial distance from the black hole at which the material is observed.

In some cases the mass M that is determined in this way is so large that it must have collapsed into a black hole to fit inside a sphere of radius r.

For example:

HST studies of M87 find strong evidence that it contains a very massive central black hole.
VLBI observations of NGC4258 reveal that it also contains a massive central black hole.

V. Celli, Univ. of Virginia
Thu Feb 11 17:44:56 EDT 1999