SCIENTISTS DISCOVER AN EARTH-SIZED PLANET - UPDATES

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                                            Scientists discover an Earth-sized planet
           





YAHOO NEWS
April 21, 2009
HATFIELD,
England

– Scientists say they've discovered a planet outside our solar system that is close to Earth in size — far different from the behemoths they had previously seen so far.

Scientists attending a conference in England said Tuesday that a planet less than twice the size of Earth has been located in a galaxy outside our solar system.

As many as 300 so called exoplanets — or planets outside our solar system — have been discovered, but most are much larger than Earth.

The BBC is quoting scientist Xavier Bonfils of the Grenoble Observatory in France as saying the new planet is the least massive exoplanet ever detected.

Researcher Michel Mayor says the new planet is probably too hot for human life because it sits very close to the sun-like star it orbits.

Mayor made the announcement at a press conference during the European Week of Astronomy and Space Science.

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                                       Scientists discover a nearly Earth-sized planet
           





Jennifer Quinn,
Associated Press Writer
April 21, 2009
HATFIELD,
England

– In the search for Earth-like planets, astronomers zeroed in Tuesday on two places that look awfully familiar to home. One is close to the right size. The other is in the right place. European researchers said they not only found the smallest exoplanet ever, called Gliese 581 e, but realized that a neighboring planet discovered earlier, Gliese 581 d, was in the prime habitable zone for potential life.

"The Holy Grail of current exoplanet research is the detection of a rocky, Earth-like planet in the 'habitable zone,'" said Michel Mayor, an astrophysicist at Geneva University in Switzerland.

An American expert called the discovery of the tiny planet "extraordinary."

Gliese 581 e is only 1.9 times the size of Earth — while previous planets found outside our solar system are closer to the size of massive Jupiter, which NASA says could swallow more than 1,000 Earths.

Gliese 581 e sits close to the nearest star, making it too hot to support life. Still, Mayor said its discovery in a solar system 20 1/2 light years away from Earth is a "good example that we are progressing in the detection of Earth-like planets."

Scientists also discovered that the orbit of planet Gliese 581 d, which was found in 2007, was located within the "habitable zone" — a region around a sun-like star that would allow water to be liquid on the planet's surface, Mayor said.

He spoke at a news conference Tuesday at the University of Hertfordshire during the European Week of Astronomy and Space Science.

Gliese 581 d is probably too large to be made only of rocky material, fellow astronomer and team member Stephane Udry said, adding it was possible the planet had a "large and deep" ocean.

"It is the first serious 'water-world' candidate," Udry said.

Mayor's main planet-hunting competitor, Geoff Marcy of the University of California, Berkeley, praised the find of Gliese 581 e as "the most exciting discovery" so far of exoplanets — planets outside our solar system.

"This discovery is absolutely extraordinary," Marcy told The Associated Press by e-mail, calling the discoveries a significant step in the search for Earth-like planets.

While Gliese 581 e is too hot for life "it shows that nature makes such small planets, probably in large numbers," Marcy commented. "Surely the galaxy contains tens of billions of planets like the small, Earth-mass one announced here."

Nearly 350 planets have been found outside our solar system, but so far nearly every one of them was found to be extremely unlikely to harbor life.

Most were too close or too far from their sun, making them too hot or too cold for life. Others were too big and likely to be uninhabitable gas giants like Jupiter. Those that are too small are highly difficult to detect in the first place.

Both Gliese 581 d and Gliese 581 e are located in constellation Libra and orbit around Gliese 581.

Like other planets circling that star — scientists have discovered four so far — Gliese 581 e was found using the European Southern Observatory's telescope in La Silla, Chile.

The telescope has a special instrument which splits light to find wobbles in different wavelengths. Those wobbles can reveal the existence of other worlds.

"It is great work and shows the potential of this detection method," said Lisa Kaltenegger, an astronomer at the Harvard-Smithsonian Center for Astrophysics.

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National Geographic






A distant world known as Gliese 581e (foreground in this artist's conception) is the lightest planet outside our solar system found to date, astronomers announced in April 2009. The planet, one of four orbiting a red dwarf star, is just less than twice the mass of Earth.

Astronomers also announced that one of the system's other planets, Gliese 581d, is an Earthlike world that orbits in the right zone to host liquid water, and thus potentially life.



Image courtesy
ESO/
L. Calçada

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                             Most Earthlike Planet Yet Found May Have Liquid Oceans






Kate Ravilious
for National Geographic News
April 21, 2009

It probably wouldn't feel exactly like home. But the planet known as Gliese 581d has a lot more in common with Earth than astronomers first thought.

New measurements of the planet's orbit place it firmly in a region where conditions would be right for liquid water, and thus life as we know it, astronomer Michel Mayor, from Geneva University in Switzerland, announced today.
 


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"It lies in the [life-supporting] habitable zone, and it could have an ocean at its surface," Mayor said during the European Week of Astronomy and Space Science conference, being held this week at the University of Hertfordshire in the U.K.

First discovered in 2007, Gliese 581d was originally calculated to be too far away from its host star—and therefore too cold—to support an ocean.

But Mayor and colleagues now show that the extrasolar planet, or exoplanet, orbits its host in 66.8 days, putting it just inside the cool star's habitable zone.

At the same time, Mayor and colleagues announced that they have spotted a fourth planet orbiting in the Gliese 581 star system—and it's the lightest exoplanet found so far.

The planet, dubbed Gliese 581e, is only about twice the mass of Earth and is the closest planet to the star, completing its orbit in about 3.15 days.

"It brings down the mass [of the lightest known exoplanet] by more than a factor of two. The previous smallest was around five Earth masses," said Andrew Collier Cameron, an astronomer at the University of Saint Andrews in the U.K. who was not involved in the find.



(Related: "Mysterious 'Super Earth' Is Smallest Known Exoplanet?")

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Near Neighbor



Gliese 581, a red dwarf star in the constellation Libra, lies around 20.5 light-years from Earth.

"In astronomical terms it is one of our near neighbors, the 87th closest known star system to the sun," said Carole Haswell, an astronomer at the Open University in Milton Keynes, U.K.

Since planets orbiting Gliese 581 are too far away to be seen directly, Mayor and colleagues originally spotted Gliese 581d by searching for tiny wobbles in the host star's motion using the European Southern Observatory (ESO) telescope at La Silla in Chile.

Weighing in at around seven Earth masses, Gliese 581d is unlikely to be made of rocks alone, the team believes.

"We can only speculate at this stage, but it may have a rocky core, encased in an icy layer, with a liquid ocean at the surface and an atmosphere," Mayor said.

Meanwhile, the much smaller and lighter Gliese 581e "probably doesn't look too different to Earth, except that it will be very hot, because it is so close to its host star," said Andrew Norton, an astronomer also at the Open University.

Norton's colleague Haswell added: "It is very exciting that such a promising candidate for an Earthlike planet has been found so close to us. It means there are likely to be many more when we search further."

And the more Earthlike planets there are, the greater the chance of discovering one that harbors life.

"I think it is only a matter of time," Norton said. "If life really does exist elsewhere in the universe, then within the next 10 to 15 years I expect we may see the first signs of life, via spectroscopic signals from exoplanets."