RE: Exotic World Said to Harbor 'Hot Ice'
----------------- Bulletin Message -----------------
From: Planet Pride
Date: May 17, 2007 12:56 AM
from: SPACE.com
Exotic World Said to Harbor 'Hot Ice'
By Ker Than
Staff Writer
posted: 16 May 2007
03:50 pm ET
A Neptune-sized world in a distant solar system orbits very close to its star and might be covered with exotic forms of water not naturally found on Earth, scientists say.
The bizarre world is being called a "hot ice planet."
The finding, to be detailed in an upcoming issue of the journal Astronomy and Astrophysics, marks the first time relatively small planets similar to the ice giants Uranus and Neptune in our solar system have been found orbiting very close to their stars.
Prior to this discovery, only gaseous giants known as "hot Jupiters" were known to inhabit such close stellar quarters.
A second look
First discovered in 2004, the planet, called GJ 436 b, is about 22 times more massive than Earth. It orbits a diminutive red dwarf star 30 light-years away from us.
New observations of the planet as it "transited," or passed in front of, its parent star allowed scientists to measure its size and mass. GJ 436 b is the closest, and smallest, transiting planet to be measured in this way.
"This discovery is an important step towards the detection and study of Earth-like planets," said study leader Michael Gillon of Liege University in Belgium.
Sara Seager, an extrasolar planet expert at the Massachusetts Institute of Technology, agrees, calling the new measurements "a huge step in the direction of finding and characterization of a habitable planet."
"It's over two times smaller than all the other planets" detected using the transit technique, she told SPACE.com. "It's a completely different kind of planet."
An artist's impression showing a close-up of a gaseous hot Jupiter planet orbit very close to its star. Scientists have now shown that smaller worlds the size of Neptune or Uranus can likewise orbit very close to their parent stars. Credit: NASA, ESA and G. Bacon (STScI)
The measurements, made using a telescope at the Observatoire Francois-Xavier Bagnoud (OFXB) in Saint-Luc, Switzerland, revealed GJ 436 b has a diameter of about 30,000 miles (50,000 kilometers)-four times that of Earth. Based on its size and mass, scientists think the planet is composed mostly of water. If the planet were a gas giant like Jupiter or Saturn and contained mostly hydrogen and helium, it would be much larger, and if it was made up of rock and iron like Earth and Mars, it would be much smaller, the scientists say.
The water world could be enveloped by a thin atmosphere of hydrogen and helium, like Neptune and Uranus, or could be surrounded entirely by water, like Saturn's moon Enceladus.
GJ 436 b orbits its star from a distance of only about 2.5 million miles (4 million km)-about 14 times closer than Mercury's average distance from the Sun. At such close quarters, scientists think its surface temperature is at least 600 degrees Fahrenheit (300 C) and any water on its atmosphere would be in the form of steam.
Exotic ice
Water on the surface of the planet is a different matter, scientists say. The pressures on GJ 436 b are so great that water would adopt forms not found anywhere on Earth except in laboratories.
"Water has more than a dozen solid states, only one of which is our familiar ice," said study team member Frederic Pont of the University of Geneva in Switzerland.
In the same way that carbon can transform into diamonds under extreme pressures, water turns into other solid states denser than both liquid and ice under very high pressures. Physicists call these alternative forms of water Ice VII and Ice X.
"If Earth's oceans were much deeper, there would be such exotic forms of solid water at the bottom," Pont said.
Seager said the existence of different forms of ice on GJ 436 b is certainly viable, but notes there are other explanations for the results.
"For example, you could have a planet that's mostly rock like our own Earth, but just a huge version of it," she said in a telephone interview.
A planet with 20 Earth masses of rock and 2 Earth masses of hydrogen and helium in its atmosphere would also match the mass and size profile measured for GJ 436 b, Seager said.
from: New Scientist Space
Strange alien world made of 'hot ice'
15:16 16 May 2007
NewScientist.com news service
David Shiga
A bizarre world of scorching hot ice shrouded in a steamy atmosphere may have been found, according to new observations. Characterising the Neptune-size planet is an important milestone on the way to detecting and characterising Earth-like planets that could harbour life.
Astronomers have discovered more than 200 planets orbiting other stars, called extrasolar planets or exoplanets. Almost all of these were detected by the way their gravity makes their parent stars wobble. But this technique, called the radial velocity method, reveals very little about the planet except for the size of its orbit and an estimate of its mass.
Transits occur when a planet appears to pass in front of its star as seen from Earth. New observations reveal that the planet around the star GJ 436 is just four times as wide as Earth – the smallest transiting planet yet known (Illustration: NASA/ESA/G Bacon)
Astronomers can learn a lot more by watching "transits" of planets that pass in front of their parent stars as seen from Earth. Careful analysis of the dimming this causes can provide clues to the planet's composition and structure. But the brightness dips are small and difficult to detect for all but the largest planets.
Now, astronomers have observed the smallest ever transiting planet. It has turned out to be a strange world, unlike anything seen before.
The planet, which orbits a small star located 30 light years from Earth called GJ 436, was actually discovered in 2004 using the radial velocity method (see Two new rocky super Earths found). At that point, astronomers deduced that it was about as massive as Neptune.
Exotic ice
But now, a team led by Michael Gillon of Geneva University in Switzerland have observed the planet transiting its host star using a telescope at the Observatoire Francois-Xavier Bagnoud (OFXB) in Saint-Luc, Switzerland.
They have been able to measure the planet's width, which provides clues to its composition and structure. It turns out to be about 50,000 kilometres wide, roughly four times the width of Earth and about the size of Neptune.
The planet is therefore too compact to be made mostly of hydrogen gas, like Jupiter, the researchers say, but not compact enough to be a rocky 'super Earth', as some had speculated. Instead, they believe it must be made mostly of an exotic form of water.
Although the parent star is much cooler than the Sun, the planet orbits 13 times closer to the star than Mercury's orbit around the Sun. That means the surface must be a blazing hot 300° C or more, keeping water in its atmosphere in vapour form.
But the high pressures in the planet's interior would compress the water so much that it would stay solid even at hundreds of degrees Celsius – the expected temperatures inside the planet. There are a variety of exotic 'hot ice' states possible in such conditions, with names like 'Ice VII' and 'Ice X'.
Ocean worlds
"Water has more than a dozen solid states, only one of which is our familiar ice," says team member Frederic Pont of Geneva University. "Under very high pressure, water turns into other solid states denser than both ice and liquid water, just as carbon transforms into diamond under extreme pressures."
The inferred composition of the planet is very much like that of Neptune, which is also made mostly of ice, Pont says. "If you bring Neptune nearer to the Sun and it's heated outside to 300° C, that's exactly what you get," he told New Scientist.
Water would not have condensed to form the GJ 436 planet so close to its star, so it must have formed farther out and migrated inwards, he says. Other similar planets out there could have stabilised at the right distance from the star to become "ocean planets", he says.
The planet orbiting GJ 436 is thought to be made mostly of water in an exotic 'hot ice' form. The composition of its atmosphere is uncertain but may contain hydrogen, helium and water vapour (Illustration: F Pont/Geneva University)
Since astronomers have only searched a tiny fraction of stars in our galaxy, finding one planet like this suggests there are many more out there, including some ocean worlds, he says. "To me, it proves that there are many planets with liquid water, because if there's one like this, it could have been a bit further from the star and then the temperature would have been right," he says.
'New era'
Sara Seager, an exoplanet expert at the Massachusetts Institute of Technology in Cambridge, US, says the finding is "tremendously exciting" because it is the first time anyone has been able to detect a transit of a planet smaller than a gas giant.
"It's heralding a new era in exoplanets," she told New Scientist. "It's opening a door to identifying habitable planets in the near future."
But she says the composition and structure of the planet are still uncertain. Although it could be mostly ice, as Gillon's team suggests, it is possible to imagine other compositions that would fit the data, she says, such as a rocky world with a massive atmosphere.
Even if water is abundant in this planet, the conditions would not be right for life to exist there, she says. It would be too hot, and it is not even clear if any of the water could be in liquid form, although deep inside where the pressure goes up, there could be a region where the water is in a quasi-liquid state. "It could pass through a strange region where it's not quite solid and not quite liquid," she says.
From: Planet Pride
Date: May 17, 2007 12:56 AM
from: SPACE.com
Exotic World Said to Harbor 'Hot Ice'
By Ker Than
Staff Writer
posted: 16 May 2007
03:50 pm ET
A Neptune-sized world in a distant solar system orbits very close to its star and might be covered with exotic forms of water not naturally found on Earth, scientists say.
The bizarre world is being called a "hot ice planet."
The finding, to be detailed in an upcoming issue of the journal Astronomy and Astrophysics, marks the first time relatively small planets similar to the ice giants Uranus and Neptune in our solar system have been found orbiting very close to their stars.
Prior to this discovery, only gaseous giants known as "hot Jupiters" were known to inhabit such close stellar quarters.
A second look
First discovered in 2004, the planet, called GJ 436 b, is about 22 times more massive than Earth. It orbits a diminutive red dwarf star 30 light-years away from us.
New observations of the planet as it "transited," or passed in front of, its parent star allowed scientists to measure its size and mass. GJ 436 b is the closest, and smallest, transiting planet to be measured in this way.
"This discovery is an important step towards the detection and study of Earth-like planets," said study leader Michael Gillon of Liege University in Belgium.
Sara Seager, an extrasolar planet expert at the Massachusetts Institute of Technology, agrees, calling the new measurements "a huge step in the direction of finding and characterization of a habitable planet."
"It's over two times smaller than all the other planets" detected using the transit technique, she told SPACE.com. "It's a completely different kind of planet."
An artist's impression showing a close-up of a gaseous hot Jupiter planet orbit very close to its star. Scientists have now shown that smaller worlds the size of Neptune or Uranus can likewise orbit very close to their parent stars. Credit: NASA, ESA and G. Bacon (STScI)
The measurements, made using a telescope at the Observatoire Francois-Xavier Bagnoud (OFXB) in Saint-Luc, Switzerland, revealed GJ 436 b has a diameter of about 30,000 miles (50,000 kilometers)-four times that of Earth. Based on its size and mass, scientists think the planet is composed mostly of water. If the planet were a gas giant like Jupiter or Saturn and contained mostly hydrogen and helium, it would be much larger, and if it was made up of rock and iron like Earth and Mars, it would be much smaller, the scientists say.
The water world could be enveloped by a thin atmosphere of hydrogen and helium, like Neptune and Uranus, or could be surrounded entirely by water, like Saturn's moon Enceladus.
GJ 436 b orbits its star from a distance of only about 2.5 million miles (4 million km)-about 14 times closer than Mercury's average distance from the Sun. At such close quarters, scientists think its surface temperature is at least 600 degrees Fahrenheit (300 C) and any water on its atmosphere would be in the form of steam.
Exotic ice
Water on the surface of the planet is a different matter, scientists say. The pressures on GJ 436 b are so great that water would adopt forms not found anywhere on Earth except in laboratories.
"Water has more than a dozen solid states, only one of which is our familiar ice," said study team member Frederic Pont of the University of Geneva in Switzerland.
In the same way that carbon can transform into diamonds under extreme pressures, water turns into other solid states denser than both liquid and ice under very high pressures. Physicists call these alternative forms of water Ice VII and Ice X.
"If Earth's oceans were much deeper, there would be such exotic forms of solid water at the bottom," Pont said.
Seager said the existence of different forms of ice on GJ 436 b is certainly viable, but notes there are other explanations for the results.
"For example, you could have a planet that's mostly rock like our own Earth, but just a huge version of it," she said in a telephone interview.
A planet with 20 Earth masses of rock and 2 Earth masses of hydrogen and helium in its atmosphere would also match the mass and size profile measured for GJ 436 b, Seager said.
from: New Scientist Space
Strange alien world made of 'hot ice'
15:16 16 May 2007
NewScientist.com news service
David Shiga
A bizarre world of scorching hot ice shrouded in a steamy atmosphere may have been found, according to new observations. Characterising the Neptune-size planet is an important milestone on the way to detecting and characterising Earth-like planets that could harbour life.
Astronomers have discovered more than 200 planets orbiting other stars, called extrasolar planets or exoplanets. Almost all of these were detected by the way their gravity makes their parent stars wobble. But this technique, called the radial velocity method, reveals very little about the planet except for the size of its orbit and an estimate of its mass.
Transits occur when a planet appears to pass in front of its star as seen from Earth. New observations reveal that the planet around the star GJ 436 is just four times as wide as Earth – the smallest transiting planet yet known (Illustration: NASA/ESA/G Bacon)
Astronomers can learn a lot more by watching "transits" of planets that pass in front of their parent stars as seen from Earth. Careful analysis of the dimming this causes can provide clues to the planet's composition and structure. But the brightness dips are small and difficult to detect for all but the largest planets.
Now, astronomers have observed the smallest ever transiting planet. It has turned out to be a strange world, unlike anything seen before.
The planet, which orbits a small star located 30 light years from Earth called GJ 436, was actually discovered in 2004 using the radial velocity method (see Two new rocky super Earths found). At that point, astronomers deduced that it was about as massive as Neptune.
Exotic ice
But now, a team led by Michael Gillon of Geneva University in Switzerland have observed the planet transiting its host star using a telescope at the Observatoire Francois-Xavier Bagnoud (OFXB) in Saint-Luc, Switzerland.
They have been able to measure the planet's width, which provides clues to its composition and structure. It turns out to be about 50,000 kilometres wide, roughly four times the width of Earth and about the size of Neptune.
The planet is therefore too compact to be made mostly of hydrogen gas, like Jupiter, the researchers say, but not compact enough to be a rocky 'super Earth', as some had speculated. Instead, they believe it must be made mostly of an exotic form of water.
Although the parent star is much cooler than the Sun, the planet orbits 13 times closer to the star than Mercury's orbit around the Sun. That means the surface must be a blazing hot 300° C or more, keeping water in its atmosphere in vapour form.
But the high pressures in the planet's interior would compress the water so much that it would stay solid even at hundreds of degrees Celsius – the expected temperatures inside the planet. There are a variety of exotic 'hot ice' states possible in such conditions, with names like 'Ice VII' and 'Ice X'.
Ocean worlds
"Water has more than a dozen solid states, only one of which is our familiar ice," says team member Frederic Pont of Geneva University. "Under very high pressure, water turns into other solid states denser than both ice and liquid water, just as carbon transforms into diamond under extreme pressures."
The inferred composition of the planet is very much like that of Neptune, which is also made mostly of ice, Pont says. "If you bring Neptune nearer to the Sun and it's heated outside to 300° C, that's exactly what you get," he told New Scientist.
Water would not have condensed to form the GJ 436 planet so close to its star, so it must have formed farther out and migrated inwards, he says. Other similar planets out there could have stabilised at the right distance from the star to become "ocean planets", he says.
The planet orbiting GJ 436 is thought to be made mostly of water in an exotic 'hot ice' form. The composition of its atmosphere is uncertain but may contain hydrogen, helium and water vapour (Illustration: F Pont/Geneva University)
Since astronomers have only searched a tiny fraction of stars in our galaxy, finding one planet like this suggests there are many more out there, including some ocean worlds, he says. "To me, it proves that there are many planets with liquid water, because if there's one like this, it could have been a bit further from the star and then the temperature would have been right," he says.
'New era'
Sara Seager, an exoplanet expert at the Massachusetts Institute of Technology in Cambridge, US, says the finding is "tremendously exciting" because it is the first time anyone has been able to detect a transit of a planet smaller than a gas giant.
"It's heralding a new era in exoplanets," she told New Scientist. "It's opening a door to identifying habitable planets in the near future."
But she says the composition and structure of the planet are still uncertain. Although it could be mostly ice, as Gillon's team suggests, it is possible to imagine other compositions that would fit the data, she says, such as a rocky world with a massive atmosphere.
Even if water is abundant in this planet, the conditions would not be right for life to exist there, she says. It would be too hot, and it is not even clear if any of the water could be in liquid form, although deep inside where the pressure goes up, there could be a region where the water is in a quasi-liquid state. "It could pass through a strange region where it's not quite solid and not quite liquid," she says.
Labels: btvol, gandolfo, The Truth Is Out There
posted by Gandolfo at 5/17/2007
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