Aside from a handful of astronauts, the only living beings to have seen an inhabited planet looming large in the sky come from science fiction.
But in other solar systems, a pair of planets could share a habitable zone – a region around a star with the right temperatures for liquid water. That proximity might help life to evolve, according to research presented at the Extreme Solar Systems III meeting in Hawaii this week.
In our solar system, planets are spaced quite far apart, with Mars orbiting 50 per cent further from the sun than Earth does and Venus 30 per cent closer. But some exoplanet systems found by NASA’s Kepler satellite have planets with tightly packed orbits. In the Kepler-36 system, for example, an outer planet circles its star just 10 per cent further out than its only known inner neighbour does.
Those planets inspired Jason Steffen of the University of Nevada, Las Vegas, working with Gongjie Li of Harvard University, to simulate what would happen to planetary systems in which two worlds shared the habitable zone.
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