Do planets have to have a stable tilt like earth to nurture life? Perhaps not as a fluctuating tilt in a planet's orbit does not prohibit the possibility of life. In fact, sometimes, it helps, a promising research say.
Further, expanding the habitable zone might almost double the number of potentially habitable planets in the galaxy, according to astronomers from University of Washington, Utah-based Weber State University and NASA.
"That is because such 'tilt-a-worlds' are less likely than fixed-spin planets to freeze over as heat from their host star is more evenly distributed," explained astronomer Rory Barnes from University of Washington.
Such a 'tilt-a-world' becomes potentially habitable because its spin would cause poles to occasionally point toward the host star, causing ice caps to quickly melt.
"Without this sort of 'home base' for ice, global glaciation is more difficult. So the rapid tilting of an exoplanet actually increases the likelihood that there might be liquid water on a planet's surface," Barnes added.
To understand this, the team used computer simulations to reproduce such planetary alignments, wondering what an earth-like planet might do if it had similar neighbours.
Their findings argue against the long-held view among astronomers that a planet needs the stabilising influence of a large moon - as earth has - to have a chance at hosting life.
"We found that planets do not have to have a stable tilt to be habitable," Barnes noted.
Minus the moon, he said, earth's tilt - now at a fairly stable 23.5 degrees - might increase by 10 degrees or so.
Climates might fluctuate but life would still be possible.
"This study suggests the presence of a large moon might inhibit life, at least at the edge of the habitable zone," said first author John Armstrong from Weber State University in a paper published online in the journal Astrobiology.
