Galaxies

A tidal tussle between M31 and M33

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Science  21 Sep 2018:
Vol. 361, Issue 6408, pp. 1212-1213
DOI: 10.1126/science.361.6408.1212-e

The morphology of the spiral arms of the Triangulum Galaxy, M33, was affected by a close pass with another nearby galaxy, M31.

CREDIT: NASA/JPL-CALTECH

The three largest galaxies in the Local Group are the Andromeda Galaxy (M31), our own Milky Way, and the Triangulum Galaxy (M33). The morphology of M33 has led to suggestions that it recently passed close to M31, but simulations have struggled to reproduce the observed properties. Semczuk et al. constructed a simulated close approach between M33 and M31. They reproduced the number and angle of M33's prominent spiral arms, the warp in its disc, its rotation rate, and more. The model is not uniquely required by the observations but demonstrates that M33's current appearance could plausibly have been generated by tidal interactions with M31.

Astrophys. J. 864, 34 (2018).

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