Proxima Centauri was the third star of Alpha Centauri, and the closest star to the Solar System. The two were separated by 4.22 light-years-more than 40 trillion kilometers!
Proxima Centauri was a red dwarf with a surface temperature of only 4,000 degrees Celsius and a reddish hue. Within its planetary system, the first planet was particularly striking.
It lay very close to Proxima Centauri and was roughly 1.3 times the size of Earth. Viewed from space, it was a life-bearing planet with one half blazing red and the other lush, green, and brimming with vitality.
The planet completed an orbit around Proxima Centauri in ten days. Interestingly, its rotation period was only slightly shorter than ten days.
This peculiar phenomenon left one half of the planet exposed to the star for long stretches of time. Surface temperatures on that half were extraordinarily high, and magma was everywhere!
Yet the planet's unique atmospheric and water circulation systems kept the other half in a climate exceptionally suited to the proliferation of life. Its environment was even more blessed than that of an ordinary life-bearing planet!
The ecosystem seemed to transfer the vitality of one side to the other. Half the planet became a forbidden zone for life, while the other half was its ideal cradle!
Because the planet rotated slightly faster than it orbited, the boundary between the two halves was constantly moving. Every three hundred Earth days or so, the planet turned halfway around, bringing the life-bearing hemisphere around to face the star's scorching heat. This also meant that life on the planet had to migrate constantly to remain on its habitable side.
At that moment, at the heart of the habitable hemisphere, stood an enormous moving metropolis. More precisely, it was a vast city built upon a moving giant tree!