Drunkenly Wobbling Planets Could Make Good Homes For Humans:
A drunken planet that’s reeling all over the place could actually be a better place for life to spring up, according to a new modelling study.
Astronomers at the University of Washington, Weber State University and NASA have found that a fluctuating tilt in a planet’s orbit doesn’t stop the world from supporting life – in fact, it might actually help.
With odd pivots in their orbit, these “tilt-a-worlds” would be leaning one way and then another, which would actually expose their surfaces to more even heat from their suns. That could mean that planets further out from their stars, outside the commonly known habitable zone, could still be kept from turning into icy glacier-locked worlds.
“Planets like these are far enough from their stars that it would be easy to write them off as frozen, and poor targets for exploration, but in fact, they might be well-suited to supporting life,” said Shawn Domagal-Goldman, an astrobiologist at NASA’s Goddard Space Flight Centre. “ .”
Tilted orbits might make some planets wobble like a top that’s almost done spinning, an effect that could maintain liquid water on the surface. (Credit: NASA’s Goddard Space Flight Centre)
In their model, the scientists looked at planets that have the same mass as Earth, orbit a sun-like star and have one or two gas giants orbiting nearby. Those massive planets can pull a world’s axis of rotation with their huge gravitational effects, changing the orientation within tens to hundreds of thousands of years – a mere blink of an eye in geological terms.
Such a tilt-a-world becomes potentially life-supporting because the spin would cause the poles to occasionally point at their sun, melting their ice caps.
“Without this sort of ‘home base’ for ice, global glaciation is more difficult,” said UW astronomer Rory Barnes. “So the rapid tilting of an exoplanet actually increases the likelihood that there might be liquid water on a planet’s surface.”
Wobbling worlds might seem far-fetched, especially to us in a system where all the planets are on roughly the same plane in space. But researchers have already spotted planetary systems where t’s happened, in orbit around the star Upsilon Andromedae. There, two enormous worlds are inclined at an angle of 30 degrees to each other, compared to the most extreme angle in our Solar System of just seven degrees.
“Knowing that this kind of planetary system existed raised the question of whether a world could be habitable under such conditions,” said Barnes.
John Armstrong of Weber State, lead author on the study, which was published in Astrobiology, said that expanding the habitable zone to include these worlds could double the number of potentially habitable planets in the galaxy.
“The habitable zone could be extended much farther from the star than we normally expect,” he said. “Rather than working against habitability, the rapid changes in the orientation of the planet could turn out be a real boon sometimes.”