Life In Other Galaxies — Where Should We Look?

Astrobiology is an emerging field that combines astronomy and biology to find signatures of life beyond Earth. Most thinking in this area has focused on individual planets or moons, but a new study asks — what if we instead thought about looking for habitable galaxies?

A new paper from the University of Belgrade explains four things current and future astrobiologists should consider when searching for life on a galactic scale.

These are: age of a galaxy (it must be old enough for life to have arisen), metallicity (it must have enough heavy elements to support the formation of gas and rocky planets), low rates of stellar explosions (too much of this and ionizing radiation sterilizes planets) and distance from the galactic center. Too close to a galaxy's center and radiation from its supermassive blackhole will irradiate planets. Close passes from other stars that destabilize planetary orbits are also more likely closer to the galactic center.

This is a very young field and the scientists say more research is needed in each of these areas. For instance, are ice worlds more protected from stellar explosions than other types of exoplanets? And just how close can life exist to the central black hole in different types of galaxies? Future researchers can use this paper as a guide on where to look for life outside the Milky Way.
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Source: "HABITABILITY OF GALAXIES AND THE APPLICATION OF MERGER TREES IN ASTROBIOLOGY," N. Stojkovic, B. Vukotic and M.M. Cirkovic (2019): https://arxiv.org/pdf/1908.05935.pdf

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Several images via public domain via NASA Scientific Visualization Studio. Exoplanet images via NASA/JPL-Caltech. HL Tau image via ALMA (NRAO/ESO/NAOJ); C. Brogan, B. Saxton (NRAO/AUI/NSF).

Thumbnail image via NASA.

Megalodon image in public domain here: https://www.flickr.com/photos/15304721@N07/5160619412

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