An evaluation of exoplanets shows that many have an eccentric orbit around their star which probably precludes life.
The research is in a new paper in the Proceedings of the National Academy of Sciences.
M dwarf stars, which make up 70% of all known stars, are at most about half the size of our Sun. They’re also much cooler, so in order to have liquid water and therefore life, exoplanets around those stars need to get very close.
The problem is that, because they’re so close, many potentially life-holding exoplanets are subject to “tidal heating”: if their orbit is too oval-shaped, they’re subject to different gravitational pull at different points in their orbit, which causes friction to heat the planet too much and boil its oceans. So while the planet is technically in the habitable zone, its orbit stops it from being actually habitable.
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