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Scientists discover ‘super-Earth’ planet
PARIS: Astronomers reported they had
discovered a “super-Earth” more than 20 light years away that is
the most intriguing world found so far in the search for
extra-terrestrial life.
About five times the mass of Earth, the planet orbits a cool, dim
“red dwarf” star located in the constellation of Libra, the team
from the European Southern Observatory (ESO) said in a press
release last week.
The star, Gliese 581, has already been identified as hosting a
planet similar in size to Neptune, the frigid gas giant on the
edge of our own Solar system.
The new planet is 14 times closer to Gliese 581 than the Earth is
to the sun. But because Gliese 581 is so cool, the planet is not
scorched by solar radiation.
It zips around the star at express speed, making just 13 days to
complete an orbit.
“We have estimated that the mean temperature of this super-Earth
lies between 0 and 40 degrees Celsius, and water would thus be
liquid,” lead researcher Stephane Udry of Switzerland’s Geneva
University, said.
“Moreover, its radius should be only 1.5 times the Earth’s radius,
and models predict that the planet should be either rocky – like
our Earth – or covered with oceans.”
“Liquid water is critical to life as we know it,” Xavier Delfosse,
a team member from France’s Grenoble University, said.
“Because of its temperature and relative proximity, this planet
will most probably be a very important target of the future space
missions dedicated to the search for extra terrestrial life.
“On the treasure map of the universe, one would be tempted to mark
this planet with an X.”
In 1995, two astronomers, also at Geneva, spotted the first
extrasolar planet, a term for a planet orbiting a star other than
our own.
Since then, 227 such planets have been spotted, according to the
Extrasolar Planets Encyclopaedia (http://exoplanet.eu/).
Gliese 581 is among the 100 closest stars to us. Its “red dwarf”
monicker comes from the fact that it is only one-third of the mass
of the sun.
Because such stars emit far less heat, they offer a far greater
chance of having planets in the so-called Goldilocks zone where
liquid water – and thus the potential for life – can exist.
The search for extrasolar planets has thrown up very few potential
home-from-homes.
The finds are typically uninhabitable, gassy giant planets, rather
than small rocky ones.
Or they orbit so close to their star that their atmosphere is
stripped away by solar radiation or, alternatively, at such a
distance that they are ice balls.
Two years ago, the same ESO team found a Neptune-sized planet
around Gliese 581, and their observations that time gave them a
hint that a smaller planet, closer to Earth in size, might also
encircle the star.
Not only did they find the “super-Earth”, they also found
indications of another planet, eight times the size of Earth, that
completes an orbit in 84 days – a discovery that makes Gliese 581
“quite a remarkable system,” ESO said.
The discovery is being reported in the journal Astronomy and
Astrophysics.
It came thanks to a highly sensitive instrument at ESO’s facility
at Silla, Chile.
The detection technique works by measuring the so-called radial
velocity of the star.
A planet orbiting around a star produces changes in the star’s
position relative to Earth.
This causes a measurable “wobble” in the starlight, from which the
orbiting object and its size can be inferred.
Even though Gliese 581 offers such promise, it would be impossible
for mankind to reach it – or even send an unmanned scout probe –
using current technology.
Chemical rockets generate only a fraction of the light speed
needed to get there within a human timescale. – AFP
 
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