by Nola Taylor Redd
September 20, 2012

from HuffingtonPost Website





Artist's rendition of the "super Earth" Gliese 163c,

which may be capable of supporting microbial life



A newly discovered alien planet may be one of the top contenders to support life beyond Earth, researchers say.


The newfound world, a "super Earth" called Gliese 163c, lies at the edge of its star's habitable zone - that just-right range of distances where liquid water could exist.

"There are a wide range of structures and compositions that allow Gliese 163c to be a habitable planet," Xavier Bonfils, of France's Joseph Fourier University-Grenoble, told by email.

He went on to caution that several possible uninhabitable combinations exist as well.





The Top 5

...Potentially Habitable Alien Planets

July 24, 2012

from Space Website

Astronomers have found more than 700 planets beyond our solar system, and thousands more await confirmation by follow-up observations.


Many of these alien worlds are too hot or too cold to support life as we know it, but researchers have found a few that appear to be much more hospitable.

On July 19, scientists at the University of Puerto Rico at Arecibo’s Planetary Habitability Laboratory released a list of the top five potentially habitable exoplanets.


Here's a brief rundown of the PHL's best candidates:


1. Gliese 581g

This rocky world was announced in September 2010 and has been controversial ever since, with some researchers casting doubt on its existence and its discoverers remaining firmly behind their find.

Gliese 581g, which is located just 20 light-years away, is likely two to three times as massive as Earth and zips around its parent star every 30 days or so.


This orbit places the planet squarely in its star's "habitable zone" - that just-right range of distances where liquid water, and perhaps life as we know it, could exist.



This artist's conception shows the inner four planets of the Gliese 581 system and their host star.

The large planet in the foreground is Gliese 581g,

which is in the middle of the star's habitable zone and is only two to three times as massive as Earth.

Some researchers aren't convinced Gliese 581g exists, however.
Credit: Lynette Cook




2. Gliese 667Cc

Gliese 667Cc, which was discovered in February 2012 by the same core team that spotted Gliese 581g, orbits a red dwarf 22 light-years away, in the constellation Scorpius (The Scorpion).

The alien world is a so-called "super Earth" that's at least 4.5 times as massive as our planet, and it completes an orbit every 28 days.


At least one other planet circles the star Gliese 667C, which is part of a triple-star system.


An artist's conception of the alien planet GJ 667Cc,

which is located in the habitable zone of its parent star.
Credit: Carnegie Institution for Science




3. Kepler-22b

Kepler-22b was spotted by NASA's planet-hunting Kepler space telescope in December 2011.


It's a super Earth about 2.4 times as wide as our planet. If the greenhouse effect operates on Kepler-22b like it does on Earth, the alien world would have an average surface temperature of 72 degrees Fahrenheit (22 degrees Celsius), researchers have said.

Kepler-22b is found about 600 light-years away, and it orbits a star very much like our own sun.


This artist's conception illustrates Kepler-22b,

a planet known to comfortably circle in the habitable zone of a sun-like star.
Credit: NASA/Ames/JPL-Caltech




4. HD 85512b

HD 85512b is another super Earth, one that's thought to be 3.6 times as massive as our planet. The alien world is found about 35 light-years from us, in the direction of the constellation Vela (The Sail).

Astronomers announced the discovery of HD 85512b in September 2011. The planet's estimated surface temperature is 77 degrees Fahrenheit (25 degrees Celsius).


This artist’s impression shows the planet HD 85512b

orbiting the Sun-like star HD 85512 about 35 light-years from Earth.

This planet is about 3.6 times as massive as the Earth

 is at the edge of the habitable zone around the star,

where liquid water, and perhaps even life, could potentially exist.
Credit: ESO/M. Kornmesser




5. Gliese 581d

This world, which is about seven times as massive as Earth, orbits a bit farther out than its planetary sibling Gliese 581g. When 581d was first discovered in 2007, many scientists regarded it as too cold to be potentially habitable.


In the years since, however, atmospheric-modeling studies have suggested that the planet may indeed be able to support life as we know it - provided 581d is warmed by a greenhouse effect.


An artist's impression of Gliese 581d,

an exoplanet discovered by the Kepler spacecraft that

is thought to be in its star's habitable zone, and a speculative moon.
Credit: Debivort | Wikimedia Commons




A newfound super Earth


Bonfils and an international team of astronomers studied nearly 400 red dwarf stars with the High Accuracy Radial Velocity Planet Searcher (HARPS), a spectograph on the 3.6-meter telescope at the European Southern Observatory's La Silla Observatory in Chile.


Gliese 163c was one of two alien planets found orbiting the star Gliese 163, which lies about 50 light-years from Earth in the Dorado constellation The team found indications of a third planet as well but cannot confirm it at this time.


Weighing in at about seven times the mass of Earth, Gliese 163c could be a rocky planet, or it could be a dwarfed gas giant, researchers said.

"We do not know for sure that it is a terrestrial planet," Bonfils said. "Planets of that mass regime can be terrestrial, ocean, or Neptune-like planets."

Orbiting at the inner edge of the habitable zone, Gliese 163c takes 26 days to zip around its parent star, which is considerably dimmer than our sun.


The second planet, Gliese 163b, has an orbital period of only nine days, while the third unconfirmed planet circles from a distance.


Bonfils pointed out that there is about a 2 percent chance that Gliese 163c might pass between its star and the sun from Earth's perspective. If so, scientists may be able to glean more information about the distant planet by watching it cross the face of its host star.


The research has been submitted for review and publication.





A good candidate for life


The Planetary Habitability Laboratory (PHL) at the University of Puerto Rico at Arecibo keeps a catalog of the alien worlds it considers good candidates to host life.


The newly discovered Gliese 163c ranks fifth on the list.

"We are finding more potentially habitable planets now than before," PHL's Abel Mendez, who was not part of the Gliese 163c discovery team, told by email..

Out of the six planets on PHL's list, four have been found in the last year alone -- Kepler-22b, Gliese 667Cc, HD 85512b, and, of course, Gliese 163c.


"Most of these are relatively close, so we can expect to find better and closer ones as our technological sensitivity to Earth-size planets improves," Mendez said.

To rank habitable planets, Mendez and his colleagues at PHL compare them with the only planet known to host life. They rank the worlds according to how similarly their masses, diameters and temperatures match up with those of Earth.


Temperatures of alien planets are tough for researchers to estimate. Temperature is heavily influenced by atmospheric characteristics, and scientists don't know much about most exoplanets' atmospheres.


Mendez suggested that one scenario for Gliese 163c might include a balmy ocean with an atmosphere 10 times as dense as Earth's. The global ocean might slosh beneath a pink, cloud-covered sky. At around 140 degrees Fahrenheit (60 degrees Celsius), the temperature would be too hot for prolonged human exposure or complex plants or animals, but some microbes could tolerate it.


But it's also possible that Gliese 163c is too hot for even those hardy lifeforms to exist.


In the meantime, Bonfils and his team intend to use HARPS to continue their search for planets that could be ripe for life, hoping to find one that may allow astronomers to study it today rather than tomorrow.

"Although it is nice to build the sample of possibly habitable planets that will be observed with the next generation of telescopes, it would be even better if we could find a planet one could characterize with today's observatories," Bonfils said.