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Friday, December 21, 2012

Extreme Life Forms Might be Able to Survive on Eccentric Exoplanets

Eccentric Habitable Zones

While Earth and the other planets in our solar system travel around the sun in near-circular orbits, planets in other systems can have more comet-like orbits in which the distance from the planet to star varies. Such orbits, termed eccentric, would cause the planet to move in and out of the habitable zone. A habitable zone, shown in green here, is defined as the region around a star where liquid water, an essential ingredient for life as we know it, could potentially be present. Earth always remains in its habitable zone.

The hypothetical planet is depicted here moving through the habitable zone and then further out into a long, cold winter. During this phase of the orbit, any liquid water on the planet will freeze at the surface; however, the possibility remains that life could, in theory, hibernate beneath the surface.

Image credit: NASA/JPL-Caltech
Astronomers have discovered a veritable rogues' gallery of odd exoplanets -- from scorching hot worlds with molten surfaces to frigid ice balls.

And while the hunt continues for the elusive "blue dot" -- a planet with roughly the same characteristics as Earth -- new research reveals that life might actually be able to survive on some of the many exoplanetary oddballs that exist.

"When we're talking about a habitable planet, we're talking about a world where liquid water can exist," said Stephen Kane, a scientist with the NASA Exoplanet Science Institute at the California Institute of Technology in Pasadena. "A planet needs to be the right distance from its star -- not too hot and not too cold." Determined by the size and heat of the star, this temperature range is commonly referred to as the "habitable zone" around a star.

Kane and fellow Exoplanet Science Institute scientist Dawn Gelino have created a resource called the "Habitable Zone Gallery." It calculates the size and distance of the habitable zone for each exoplanetary system that has been discovered and shows which exoplanets orbit in this so-called "goldilocks" zone. The Habitable Zone Gallery can be found at www.hzgallery.org . The study describing the research appears in the Astrobiology journal and is available at http://arxiv.org/abs/1205.2429 .