Juri Toomre and Alar Toomre demonstrated how close gravitational encounters between galaxies can generate long bridges and tails. Their 1972 calculations represented each galactic disk by noninteracting test particles orbiting a central mass, then followed its response to another passing galaxy.
Despite this deliberately simplified model, tidal forces produced narrow extended structures resembling observed interacting systems. The paper reconstructed several particular pairs, connecting recognizable morphology to encounter geometry. It showed that dramatic luminous extensions can arise from ordinary gravity acting on pre-existing disk material.[ref]
Portrait of Juri Toomre
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