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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
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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 .
