In my 2013 science-fiction novel Proxima I imagined a habitable planet orbiting the red dwarf Proxima Centauri, the nearest star to our solar system. Human colonists call this world Per Ardua, after the 鈥� 鈥渢hrough struggle to the stars鈥�.
Fiction has now turned into partial fact with the discovery of a planet in this very spot by a team of astronomers led by . They have given it the more functional name Proxima b.
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It is fascinating to see my imagined world coming true. Until recently, we thought that no such planet could be habitable because it must be tidally locked, keeping the same face pointing at its star, leading to extremes of temperature. A flood of discoveries of entirely new world types among the is revising that view.
Proxima was partially inspired by a around such a planet, and, along with a magnetic field, might shield the surface from stellar flares and high levels of ultraviolet and X-ray radiation.
I put Per Ardua 6 million kilometres from its star, compared to the 7.3 million km estimated by Anglada-Escude鈥檚 team for Proxima b. Both are in the habitable zone. I gave it a mass 8 per cent less than Earth鈥檚, compared to 30 per cent higher for Proxima b.
The astronomers know the planet鈥檚 mass and orbital period and that it is probably tidally locked, but not much more. Of course it is fun to speculate further.
Archery target
With one face permanently turned to Proxima, Per Ardua鈥檚 鈥渟ubstellar point鈥�, directly facing the star, is a focus of climate patterns. Around it lie concentric bands of types of life, adapted to particular levels of starlight, with analogues of tropical forest at the centre, and temperate forests and taiga further out. From space, the illuminated face of Per Ardua looks like an archery target, though the bands are broken up across land and oceans.
Life on Per Ardua exploits its peculiar conditions. One plant spreads tough photosynthesising sheets, like lily pads, across the ground, to stifle competitors and monopolise the unchanging light.
The terminator zone, between permanent light and dark, features sunlit mountains and valleys of perpetual dark; these 鈥渓ight islands鈥� are evolutionary laboratories, like isolated islands on Earth. Solar flares inflict long term changes on the climate, like our ice ages, to which life has to adapt.
I was thrilled when Anglada-Escud茅 told me that my climate description was plausible for a Proxima planet, given the parameters the team has explored with its simulations.
But the real thrill of finding Proxima b is that since red dwarfs are by far the most numerous stars in the Milky Way and are much more long-lived than the sun, if they can host planets with the potential for life, then suddenly our galaxy looks much more hospitable.
And if we have found an Earth-like planet orbiting the very nearest of these stars to our sun, such planets must be everywhere.
