Clouds, storms, swirls - go to the jpl/nasa link for more.
Showing posts with label planets. Show all posts
Showing posts with label planets. Show all posts
Sunday, April 26, 2009
Wednesday, April 22, 2009
"Scientists discover a nearly Earth-sized planet"
(AP) 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...
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...
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...
"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...
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...
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...
Tuesday, June 17, 2008
"A Bounty of Midsize Planets Is Reported"
From the New York Times
About a third of all the Sun-like stars in our galaxy harbor modestly sized planets, according to a study announced Monday by a team of European astronomers....
At a meeting in Nantes, France, Michel Mayor of the Geneva Observatory and his group presented a list of 45 new planets, ranging in mass from slightly bigger than Earth to about twice as massive as Neptune, from a continuing survey of some 200 stars.
All of the planets orbit their stars in 50 days or less, well within the corresponding orbit of Mercury, which takes 88 days to go around the Sun, and well within frying distance of any lifelike creatures.
Among the bounty is a rare triple-planet system of “super-Earths” around the star HD 40307, about 42 light-years away in the constellation Pictor. The planets are roughly four, seven and nine times the mass of Earth and have orbital periods of 4, 10 and 20 days, respectively.
Dr. Mayor called the discoveries “only the tip of the iceberg” in a news release from the European Southern Observatory in Garching, Germany.
Theories of planet formation, Dr. Mayor said in an e-mail message from Nantes, hold that smaller planets like super-Earths and Neptunes should be numerous. “But evidently it was a nice surprise to see that with our instrument we have the sensitivity to detect that population,” he said.
Astronomers said the new results indicated that when their instruments got sensitive enough to detect even smaller planets, such planets would be there to be found.
Sara Seager, a planetary theorist at the Massachusetts Institute of Technology who was one of the organizers of the Nantes conference, said in an e-mail message, “We’ve always been hoping that low-mass planets are common — to increase the chance for an Earth analog to exist around a nearby star.”
Tuesday, January 22, 2008
Stars Eating/Giving Birth to New Planets
"Stars stay young by eating planets"
A new research has indicated that stars can slow down their aging process by consuming Jupiter-sized planets.
According to a report in New Scientist , most stars eventually become white dwarfs, but along the way expand into red giants, while their cores shrink and undergo a short but intense phase of helium fusion.
"Yet gobbling up a Jupiter-sized planet as they expand can affect that process," said Brad Hansen at the University of California, Los Angeles.
Calculations by Hansen suggest that if the planet is swallowed at the right moment, its gravity can peel off the star's outer layers.
Then, the star's exposed core never gets hot enough to fuse helium, so the resulting white dwarf is less massive and looks younger than it should for its age.
A group of white dwarfs with precisely those characteristics was observed three years ago in the star cluster NGC 6791.
The work was presented at the annual American Astronomical Society meeting in Austin, Texas last week.
____________
"Amazing old stars give birth again"
http://www.usatoday.com/tech/science/space/2008-01-21-old-stars-birth_N.htm
Two old stars appear to be gearing up for a second generation of planet formation, a phenomenon astronomers say they have never seen before.
"This is a new class of stars, ones that display conditions now ripe for formation of a second generation of planets, long, long after the stars themselves formed," said UCLA astronomy graduate student Carl Melis, who reported the findings at a recent meeting of the American Astronomical Society in Austin, Texas.
The stars are BP Piscium in the constellation Pisces and TYCHO 4144 329 2, which resides in the constellation Ursa Major. The exact ages of the stars are unknown, but it is estimated they are at least hundreds of millions or possibly billions of years old, and might have already given birth to planets long ago.
"Most astronomers now believe that most stars are accompanied by first-generation planets of some sort, even if the planets are not massive enough to be picked up by the radial velocity [detection] technique," Melis said.
Second generation of planets
The unusual thing about these stars is that they appear to be giving birth to planets again.
"We currently understand planet formation to occur around stars when they are very young and enshrouded in dusty and gaseous disks, the material necessary to form planetary bodies," Melis told SPACE.com. "This material is completely used up after a couple to ten million years after the star is born and is not replenished during the star's life. As such, we would never expect a star to undergo planet formation late in its life as the necessary conditions are not present."
A new research has indicated that stars can slow down their aging process by consuming Jupiter-sized planets.
According to a report in New Scientist , most stars eventually become white dwarfs, but along the way expand into red giants, while their cores shrink and undergo a short but intense phase of helium fusion.
"Yet gobbling up a Jupiter-sized planet as they expand can affect that process," said Brad Hansen at the University of California, Los Angeles.
Calculations by Hansen suggest that if the planet is swallowed at the right moment, its gravity can peel off the star's outer layers.
Then, the star's exposed core never gets hot enough to fuse helium, so the resulting white dwarf is less massive and looks younger than it should for its age.
A group of white dwarfs with precisely those characteristics was observed three years ago in the star cluster NGC 6791.
The work was presented at the annual American Astronomical Society meeting in Austin, Texas last week.
____________
"Amazing old stars give birth again"
http://www.usatoday.com/tech/science/space/2008-01-21-old-stars-birth_N.htm
Two old stars appear to be gearing up for a second generation of planet formation, a phenomenon astronomers say they have never seen before.
"This is a new class of stars, ones that display conditions now ripe for formation of a second generation of planets, long, long after the stars themselves formed," said UCLA astronomy graduate student Carl Melis, who reported the findings at a recent meeting of the American Astronomical Society in Austin, Texas.
The stars are BP Piscium in the constellation Pisces and TYCHO 4144 329 2, which resides in the constellation Ursa Major. The exact ages of the stars are unknown, but it is estimated they are at least hundreds of millions or possibly billions of years old, and might have already given birth to planets long ago.
"Most astronomers now believe that most stars are accompanied by first-generation planets of some sort, even if the planets are not massive enough to be picked up by the radial velocity [detection] technique," Melis said.
Second generation of planets
The unusual thing about these stars is that they appear to be giving birth to planets again.
"We currently understand planet formation to occur around stars when they are very young and enshrouded in dusty and gaseous disks, the material necessary to form planetary bodies," Melis told SPACE.com. "This material is completely used up after a couple to ten million years after the star is born and is not replenished during the star's life. As such, we would never expect a star to undergo planet formation late in its life as the necessary conditions are not present."
Friday, December 07, 2007
"'Flying Saucers' Around Saturn Explained"
The formation of strange flying-saucer-shaped moons embedded in Saturn's rings have baffled scientists. New findings suggest they're born largely from clumps of icy particles in the rings themselves, an insight that could shed light on how Earth and other planets coalesced from the disk of matter that once surrounded our newborn sun.
Saturn's rings orbit the planet in a flat disk that corresponds to the planet's equator. Likewise, Earth and the other planets orbit the sun in a fairly flat plane that relates to the sun's equator. The planets, at least the rocky ones, are thought to have formed when bits of material orbiting the newborn sun stuck together, forming larger and larger objects that collided and coalesced.
Observations by NASA's Cassini spacecraft revealed the Saturnian moons Atlas and Pan, each roughly 12 miles (20 kilometers) from pole to pole, have massive ridges bulging from their equators some 3.7 to 6.5 miles (6 to 10.5 kilometers) high, giving them the flying-saucer appearance.
In principle, fast rates of spin might have stretched Atlas and Pan out into such unusual shapes, just as tossing a disk of pizza d ough flattens it out. But neither moon whirls very quickly, each taking about 14 hours to complete a rotation. Earth, far bigger, rotates in 24 hours, of course.
Carolyn Porco, a planetary scientist at the Space Science Institute in Boulder, Colo., and her colleagues suspected these peculiar moons could be formed mostly from Saturn's rings, rather than just from fragments produced in collisions of larger moons, as some have suggested. The location of the ridges lined up precisely with the rings of icy particles in which they were embedded, findings which are detailed in the Dec. 6 issue of the journal Science.
After analyzing the shapes and densities of the moons from data captured by Cassini, Porco's team now finds Pan and Atlas appear to be mostly light, porous, icy bodies, just like the particles making up the rings. Computer simulations suggest one-half to two-thirds of these bizarre moons are made of ring material, piled up on massive, dense fragments of bigger moons that disintegrated billions of years ago after catastrophic collisions with one another.
These findings could shed light on the behavior of "accretion disks"—disks that build up as matter falls toward a gravitational pull.
"Accretion disks are found everywhere in the universe—around black holes, around stars, around Jupiter," said astrophysicist Sebastien Charnoz at University of Paris Diderot in France. He is the lead author of a related new study—also described in the Dec. 6 issue of Science—that shows how the Saturnian ice-clump moons elongated and bulged out into the flying-saucer shapes.
Understanding how the icy particles piled up to make these shapes could shed light on how matter in the protoplanetary disk that accreted around our newborn sun could have clumped together to make planets, Charnoz added.
Saturn's rings orbit the planet in a flat disk that corresponds to the planet's equator. Likewise, Earth and the other planets orbit the sun in a fairly flat plane that relates to the sun's equator. The planets, at least the rocky ones, are thought to have formed when bits of material orbiting the newborn sun stuck together, forming larger and larger objects that collided and coalesced.
Observations by NASA's Cassini spacecraft revealed the Saturnian moons Atlas and Pan, each roughly 12 miles (20 kilometers) from pole to pole, have massive ridges bulging from their equators some 3.7 to 6.5 miles (6 to 10.5 kilometers) high, giving them the flying-saucer appearance.
In principle, fast rates of spin might have stretched Atlas and Pan out into such unusual shapes, just as tossing a disk of pizza d ough flattens it out. But neither moon whirls very quickly, each taking about 14 hours to complete a rotation. Earth, far bigger, rotates in 24 hours, of course.
Carolyn Porco, a planetary scientist at the Space Science Institute in Boulder, Colo., and her colleagues suspected these peculiar moons could be formed mostly from Saturn's rings, rather than just from fragments produced in collisions of larger moons, as some have suggested. The location of the ridges lined up precisely with the rings of icy particles in which they were embedded, findings which are detailed in the Dec. 6 issue of the journal Science.
After analyzing the shapes and densities of the moons from data captured by Cassini, Porco's team now finds Pan and Atlas appear to be mostly light, porous, icy bodies, just like the particles making up the rings. Computer simulations suggest one-half to two-thirds of these bizarre moons are made of ring material, piled up on massive, dense fragments of bigger moons that disintegrated billions of years ago after catastrophic collisions with one another.
These findings could shed light on the behavior of "accretion disks"—disks that build up as matter falls toward a gravitational pull.
"Accretion disks are found everywhere in the universe—around black holes, around stars, around Jupiter," said astrophysicist Sebastien Charnoz at University of Paris Diderot in France. He is the lead author of a related new study—also described in the Dec. 6 issue of Science—that shows how the Saturnian ice-clump moons elongated and bulged out into the flying-saucer shapes.
Understanding how the icy particles piled up to make these shapes could shed light on how matter in the protoplanetary disk that accreted around our newborn sun could have clumped together to make planets, Charnoz added.
Monday, October 01, 2007
"Why Earth beats Mars when it comes to hospitality"
Life on Earth was made possible by the planet’s ability to stockpile oxygen beneath its surface, researchers say.
Oxygen is transported, as part of iron oxide, by geological movements deep beneath the Earth’s crust where pressure and heat transform it into an ingredient of the mineral majorite. When majorite is moved close to the surface it becomes unstable and begins to release oxygen, which can then bind with hydrogen to form water.
“Without this mechanism our ‘Blue Planet’ might well be as dry and inhospitable as Mars,” a study in the journal Nature concluded.
Christian Ballhaus, of the Mineralogical Institute at Bonn University, said that the movement of the mineral to the top of the mantle, between the Earth’s core and crust, was crucial. “That’s where the stored oxygen is released,” he said. “Near the surface it is made available for all the oxidation reactions that are essential for life on Earth.
“If our planet did not have the ability to store oxygen in the deep reaches of its mantle there would probably be no life on its surface.”
The multinational research team described the process as an “oxygen elevator”, without which “the Earth would probably be a barren planet, hostile to life”.
The size of the Earth is an essential factor, they said. Much smaller, and the heat and pressure generated are inadequate for the necessary geological processes. The Earth, with a diameter of 7,926 miles (12,756km), still has a changing mantle whereas Mars, with a diameter of 4,350 miles, cooled down long ago and no longer has any movement. Professor Ballhaus said of Mars: “Its crust has therefore lost the ability to transport oxygen and maintain a lasting, water-rich atmosphere.”
Arno Rohrbach, of the University of Bonn, added: “According to our findings, planets below a certain size hardly have any chance of forming a stable atmosphere with a high water content. The pressure in their mantle is just not high enough to store sufficient oxygen in the rock and release it again at the surface.”
Friday, September 07, 2007
"Turbulence Key to Planet Formation..."
Swirling eddies and chaotic vortices are crucial to the formation of new planets, suggests a counterintuitive new study.
Such turbulence is vital to helping planets go from "toddler" to "teenage" size by helping rocks and boulders stick together, the computer simulation hints.
A few scientists recently suspected that turbulence might help in planet formation, but no one had showed in detail how that might work until now.
"We were the first to model how interacting boulders move around in this turbulence," said Anders Johansen of the Max Planck Institute for Astronomy in Germany, who led the research team that made the new findings. The study appeared last week in the journal Nature.
The research showed that turbulence could create "planetesimals," or planetary precursors, very quickly—in only seven orbits around a star, or around just a hundred years.
New solar systems form from a swirling disk of dust and gas surrounding a central star. (Related: "Planet-Forming Disk Spotted Around Dead Star" [April 5, 2006].)
As the matter swirls around, microscopic bits of dust hit each other and stick together. Gradually they can gather into rocks and boulders, around a yard (a meter) across.
"We have a pretty good grasp of this [process]," Johansen said.
But explaining how matter forms bigger clumps—up to planetesimals about a kilometer across—has eluded scientists.
"That has been known to be a big problem for the last 30 years," Johansen said.
Part of the issue is that when larger boulders collide with each other, "they don't stick to each other very well, but are likely to destroy each other when they collide," Johansen said.
And around this size, the rocks would begin to experience drag from the gas around them.
In the new computer model, scientists studied what would happen if this disk of orbiting matter does not spin calmly around but instead has turbulence stirring things up.
Although researchers haven't figured out for sure what might cause such turbulence, they're confident that there would be a fair amount of it in the disks surrounding young stars.
The turbulence has high-pressure areas where boulders tend to accumulate, the simulation revealed.
Once a few boulders get stuck together in such locations, the formation can help other boulders stick too, since they shield each other from the gas.
The areas also help the boulders resist the headwind from the gas around them, like "drafting" racers...
Gravity would then pull the boulders closer together, until they gradually collapsed into planetesimals a couple of hundred miles (a few hundred kilometers) across.
Planetesimals that large would attract even more rocks with their gravity, allowing them to grow into full-fledged planets...
"It's kind of ironic," Throop said. "We're used to explaining things on the size of galaxies, and on really small scales the size of light waves.
"In planetesimal formation, however, the tricky part is these medium-sized grains," around a yard (a meter) across, he added.
This new study is "a big step," Throop said, toward figuring out how budding planetesimals pass through their "toddler" stage and grow to full-size planets.
Thursday, August 30, 2007
"Planet Formation Mystery Solved"
A new computer-modeled theory shows how rocky boulders around infant stars team up to form planets without falling into stars.
"This has been a stumbling block for 30 years," said Mordecai-Marc Mac Low, an astrophysicist at the American Museum of Natural History in New York City, of planet formation theories. "The reason is that boulders tend to fall into the star in a celestial blink of an eye. Some mechanism had to be found to prevent them from being dragged into a star."
The solution: Together, many boulders can join to fight a cosmic headwind that otherwise would doom them.
Truckin' boulders
The stuff of rocky planets originates in an accretion disk, or collection of gas and dust that circles around a newborn star. Over time the dust particles bunch together and form large boulders, but eventually they meet "wind" resistance from the disk's mist of gas.
"They see a headwind. It's deadly and drags them into the star," Mac Low told SPACE.com.
Modeling the turbulence within the gas, however, showed that boulders can team up and form planets.
"Turbulence in the disk concentrates boulders in regions of higher pressure," Mac Low said, noting that such a disturbance is enough to enable the boulders to fight the dooming headwind. "If the gas is sped up, the boulders don't see a headwind. By getting the gas going with them they conserve energy and stay in orbit."
Mac Low compared the effect to a chain of semi-trucks driving down a highway. Each boulder is like a semi-truck "pushing" the gas in front of it, creating a friendly pocket of air behind it that other semis can travel in without using up as much fuel. "The end of the story is that enough boulders gather together, gravity takes over and they collapse into planet-like bodies," Mac Low said.
Mac Low and his colleagues' findings will be detailed in an upcoming issue of the journal Nature.
"This has been a stumbling block for 30 years," said Mordecai-Marc Mac Low, an astrophysicist at the American Museum of Natural History in New York City, of planet formation theories. "The reason is that boulders tend to fall into the star in a celestial blink of an eye. Some mechanism had to be found to prevent them from being dragged into a star."
The solution: Together, many boulders can join to fight a cosmic headwind that otherwise would doom them.
Truckin' boulders
The stuff of rocky planets originates in an accretion disk, or collection of gas and dust that circles around a newborn star. Over time the dust particles bunch together and form large boulders, but eventually they meet "wind" resistance from the disk's mist of gas.
"They see a headwind. It's deadly and drags them into the star," Mac Low told SPACE.com.
Modeling the turbulence within the gas, however, showed that boulders can team up and form planets.
"Turbulence in the disk concentrates boulders in regions of higher pressure," Mac Low said, noting that such a disturbance is enough to enable the boulders to fight the dooming headwind. "If the gas is sped up, the boulders don't see a headwind. By getting the gas going with them they conserve energy and stay in orbit."
Mac Low compared the effect to a chain of semi-trucks driving down a highway. Each boulder is like a semi-truck "pushing" the gas in front of it, creating a friendly pocket of air behind it that other semis can travel in without using up as much fuel. "The end of the story is that enough boulders gather together, gravity takes over and they collapse into planet-like bodies," Mac Low said.
Mac Low and his colleagues' findings will be detailed in an upcoming issue of the journal Nature.
Thursday, March 29, 2007
Jupiter's Auroras
__________________________________________
From NASA:
...Jupiter's hyper-auroras never stop. "We see them every time we look," says Gladstone. You don't see auroras in Alaska every time you look, yet on Jupiter the Northern Lights always seem to be "on."
Gladstone explains the difference: On Earth, the most intense auroras are caused by solar storms. An explosion on the sun hurls a billion-ton cloud of gas in our direction, and a few days later, it hits. Charged particles rain down on the upper atmosphere, causing the air to glow red, green and purple. On Jupiter, however, the sun is not required. "Jupiter is able to generate its own lights," says Gladstone.
The process begins with Jupiter's spin: The giant planet turns on it axis once every 10 hours and drags its planetary magnetic field around with it. As any science hobbyist knows, spinning a magnet is a great way to generate a few volts—it's the basic principle of DC motors. Jupiter's spin produces 10 million volts around its poles.
"Jupiter's polar regions are crackling with electricity," says Gladstone, "and this sets the stage for non-stop auroras."
The polar electric fields grab any charged particles they can find and slam them into the atmosphere. Particles for slamming can come from the sun, but Jupiter has another, more abundant source nearby: the volcanic moon Io, which spews oxygen and sulfur ions (O+ and S+) into Jupiter's spinning magnetic field.
Somehow, these ions make their way to Jupiter's poles where electric fields send them hurtling toward the planet below. Upon entering the atmosphere, "their electrons are first stripped away by molecules they run into, but as they slow down they start grabbing electrons back. The 'charge exchange reaction' produces intense X-ray auroras," he explains...
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