If there is life on K2-18b the K2-18 red dwarf star will kill it off

25 April 2025

News that traces of chemicals possibly indicating the presence of life on a planet, known as K2-18b, some one-hundred-and-twenty-four light years from Earth, resulted in a flurry of headlines the other week. Scientists find strongest evidence yet of life on an alien planet. Scientists claim they’ve discovered most promising ‘hints’ of potential for life on distant planet. And: Scientists Find Promising Indication of Extraterrestrial Life — 124 Light-Years Away.

Sure, it’s exciting. This is news many of us have been waiting for. Even if it’s not quite the definitive announcement we would have preferred. The problem though is the media outlets writing about the discovery of chemical “fingerprints” in the atmosphere of K2-18b, have not looked at the whole story. In fact, it seems they’ve only looked at the first few words. After all, why allow the full facts of the matter to get in the way of a click-bait worthy headline? The biggest — literally — part of the story is K2-18, the star the would-be life-hosting planet K2-18b is orbiting.

I’ve written about this before, but let’s revisit the subject, since it’s topical.

K2-18 is a red dwarf star. Red dwarfs — as the name suggests — are small. Some might only be a little bigger than Jupiter, the largest planet in the solar system. Red dwarfs are dimmer and cooler compared to a star like the Sun. They however have long lifespans, typically measured in trillions of years, rather than billions, as is the case for many other stars in the universe. At first glance, red dwarfs seem like ideal stars to host planets that might give rise to life. Their longevity gives lifeforms an eon to take hold and develop. But red dwarfs are not really life-friendly stars.

One problem lies in their size. Being so small, the habitable, or Goldilocks zone, the area of their solar system best suited for the fostering of life, that is neither too hot, nor too cool, is quite close to the star. Any planets in the habitable zone will be tidally locked. This means one side of the planet permanently faces the star, while the other is perpetually shrouded in darkness. In other words, the star facing side of a planet will be incredibly warm, while the dark side will be quite cold. Neither extreme may be particularly conducive to life, especially complex lifeforms.

But that’s not the worst of it. Red dwarfs also emit powerful flares that can render nearby planets lifeless. Some of these outbursts can be even more intense than those generated by the Sun. While one study of these flares found they might emanate from the polar regions of red dwarfs, rather than their equators, being the plane planets usually orbit a star along, the odds remain stacked against life here. None of this information is new, but has just about been completely overlooked in the recent news stories, about the possibility of life on K2-18b.

Here may be an unfortunate instance of a star that brings life into being, only to take it away later.

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astronomy, current affairs, science