Habitability impacts of molecular clouds

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Science  12 Apr 2019:
Vol. 364, Issue 6436, pp. 142
DOI: 10.1126/science.364.6436.142-b

The Sun is currently located in a low-density region of interstellar space, but conditions would be very different if it were inside a giant molecular cloud (GMC). These vast assemblages of relatively dense gas and dust are concentrated within the Milky Way's spiral arms. Passing through a GMC would block visible light from other stars, owing to dust absorption, and reduce the habitability of Earth by scattering comets onto impact orbits. Kokaia and Davies calculated the expected encounter rate between the Sun and GMCs: 1.6 ± 1.3 per billion years, lasting a few million years each time. Fortunately for life on Earth, these disruptive encounters are rare.

Mon. Not. R. Astron. Soc., in press, arXiv:1903.08026 (2019).

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