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Re-thinking an Alien World.
Presented by Science at NASA.
Forty light years from Earth, a rocky world named "55 Cancri e"
circles perilously close to a stellar inferno.
Completing one orbit in only 18 hours, the alien planet is
26 times closer to its parent star than Mercury is to the Sun.
If Earth were in the same position, the soil beneath our
feet would heat up to about 3200 F.
Researchers have long thought that 55 Cancri e must be a
wasteland of parched rock.
Now they're thinking again.
New observations by NASA's Spitzer Space Telescope suggest
that 55 Cancri e may be wetter and weirder than anyone imagined.
Spitzer recently measured the extraordinarily small amount
of light 55 Cancri e blocks when it crosses in front of its star.
These transits occur every 18 hours, giving researchers
repeated opportunities to gather the data they need to
estimate the width, volume and density of the planet.
According to the new observations, 55 Cancri e has a mass
7.8 times and a radius just over twice that of Earth.
Those properties place 55 Cancri e in the "super-Earth"
class of exoplanets, a few dozen of which have been found.
Only a handful of known super-Earths, however, cross the
face of their stars as viewed from our vantage point in the
cosmos, so 55 Cancri e is better understood than most.
When 55 Cancri e was discovered in 2004, initial estimates
of its size and mass were consistent with a dense planet of solid rock.
Spitzer data suggest otherwise: About a fifth of the
planet's mass must be made of light elements and compounds, including water.
Given the intense heat and high pressure these materials
likely experience, researchers think the compounds likely
exist in a "supercritical" fluid state.
A supercritical fluid is a high-pressure, high-temperature
state of matter best described as a liquid-like gas, and a
marvelous solvent.
Water becomes supercritical in some steam turbines, and it
tends to dissolve the tips of the turbine blades.
Supercritical carbon dioxide is used to remove caffeine
from coffee beans, and sometimes to dry-clean clothes.
Liquid-fueled rocket propellant is also supercritical when
it emerges from the tail of a spaceship.
On 55 Cancri e, this stuff may be literally oozing, or is
it steaming out of the rocks.
With supercritical solvents rising from the planet's
surface, a star of terrifying proportions filling much of
the daytime sky, and whole years rushing past in a matter
of hours, 55 Cancri e teaches a valuable lesson: Just
because a planet is similar in size to Earth does not mean
the planet is like Earth.
It's something to re-think about.
For more news about alien worlds, visit science.nasa.gov