May 21, 2018 03:18 PM
https://cosmosmagazine.com/space/planets...-snowballs
EXCERPT: Earthlike planets circling other stars may be prone to wild climate fluctuations that could make them uninhabitable, even if they lie within the so-called “habitable zone”, scientists say. Sometimes referred to as the Goldilocks Zone, the habitable zone is the region in which a planet is neither so close to its sun that it is permanently parched nor so far away it doesn’t receive enough energy for liquid water to exist.
But another factor affecting habitability, says Rory Barnes, an astrobiologist [...], is the planet’s obliquity – the angle between the planet’s spin and its orbit. On Earth, this is the well-known 23.5 degrees that establishes our seasons [...] For us, the condition is both fairly mild and fairly stable over time. “The moon keeps our obliquity fairly constant,” Barnes says. [...] other solar systems might not be so tidy. In fact, exoplanet hunters are coming to believe that planets could be flying around at all sorts of angles. [...] small wobbles known as Milankovitch cycles have since the 1970s been associated with the beginning and ending of ice ages.
[...] “As we find more and more systems with potentially habitable worlds we need to identify which are the ones we want to observe first,” he notes. “If there’s a huge possibility of a snowball state because of the orbital dynamics, we may say here’s one to cross off the list and go on to the next one.”
MORE: https://cosmosmagazine.com/space/planets...-snowballs
EXCERPT: Earthlike planets circling other stars may be prone to wild climate fluctuations that could make them uninhabitable, even if they lie within the so-called “habitable zone”, scientists say. Sometimes referred to as the Goldilocks Zone, the habitable zone is the region in which a planet is neither so close to its sun that it is permanently parched nor so far away it doesn’t receive enough energy for liquid water to exist.
But another factor affecting habitability, says Rory Barnes, an astrobiologist [...], is the planet’s obliquity – the angle between the planet’s spin and its orbit. On Earth, this is the well-known 23.5 degrees that establishes our seasons [...] For us, the condition is both fairly mild and fairly stable over time. “The moon keeps our obliquity fairly constant,” Barnes says. [...] other solar systems might not be so tidy. In fact, exoplanet hunters are coming to believe that planets could be flying around at all sorts of angles. [...] small wobbles known as Milankovitch cycles have since the 1970s been associated with the beginning and ending of ice ages.
[...] “As we find more and more systems with potentially habitable worlds we need to identify which are the ones we want to observe first,” he notes. “If there’s a huge possibility of a snowball state because of the orbital dynamics, we may say here’s one to cross off the list and go on to the next one.”
MORE: https://cosmosmagazine.com/space/planets...-snowballs
