Reports

Chaos and the Shapes of Elliptical Galaxies

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Science  19 Jan 1996:
Vol. 271, Issue 5247, pp. 337-340
DOI: 10.1126/science.271.5247.337

Abstract

Hubble Space Telescope observations reveal that the density of stars in most elliptical galaxies rises toward the center in a power-law cusp. Many of these galaxies also contain central dark objects, possibly supermassive black holes. The gravitational force from a steep cusp or black hole will destroy most of the box orbits that constitute the “backbone” of a triaxial stellar system. Detailed modeling demonstrates that the resulting chaos can preclude a self-consistent, strongly triaxial equilibrium. Most elliptical galaxies may therefore be nearly axisymmetric, either oblate or prolate.

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