Planets with many neighbors may be the best places to look for life

If you’re looking for life beyond the solar system, there’s strength in numbers.

A new study suggests that systems with multiple planets tend to have rounder orbits than those with just one, indicating a calmer family history. Only child systems and planets with more erratic paths hint at past planetary sibling clashes violent enough to knock orbits askew, or even lead to banishment.

A long-lasting abundance of sibling planets might therefore have protected Earth from destructive chaos, and may be part of what made life on Earth possible, says astronomer Uffe Gråe Jørgensen of the Niels Bohr Institute in Copenhagen.

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JPL-CALTECH/NASA

Planetary families with lots of siblings, like the TRAPPIST-1 exoplanet system shown in this illustration, tend to have more circular orbits than singleton worlds. That could mean they’re better places to look for life.

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Astronomers using the Hubble Space Telescope have conducted the first spectroscopic survey of Earth-sized planets in the TRAPPIST-1 system's habitable zone.

Hubble reveals that at least the inner five planets do not seem to contain puffy, hydrogen-rich atmospheres similar to gaseous planets such as Neptune.

This means the atmospheres may be more shallow and rich in heavier gases like carbon dioxide, methane, and oxygen.