2013년 3월 28일 목요일

Green Meteorite May Be from Mercury, a First

Scientists may have discovered the first meteorite from Mercury.
The green rock found in Morocco last year may be the first known visitor from the solar system's innermost planet, according to meteorite scientist Anthony Irving, who unveiled the new findings this month at the 44th annual Lunar and Planetary Science Conference in The Woodlands, Texas. The study suggests that a space rock called NWA 7325 came from Mercury, and not an asteroid or Mars.
NWA 7325 is actually a group of 35 meteorite samples discovered in 2012 in Morocco. They are ancient, with Irving and his team dating the rocks to an age of about 4.56 billion years.
"It might be a sample from Mercury, or it might be a sample from a body smaller than Mercury but [which] is like Mercury," Irving said during his talk. A large impact could have shot NWA 7325 out from Mercury to Earth, he added.
Irving is an Earth and Space Sciences professor at the University of Washington and has been studying meteorites for years. But the NWA 7325 meteorite is unlike anything found on Earth before,  he told SPACE.com.
Meteorites from Mars are imbued with some Martian atmosphere, making them somewhat simple to tell apart from other rocks. Space rocks from Vesta, one of the largest asteroids in the solar system, are also chemically distinct, but NWA 7325 does not resemble any space rock documented by scientists today.
Irving thinks that the meteoritewas created and eventually ejected from a planet or other body that had flowing magma on its surface at some point in its history. Evidence suggests that the rock could have been formed as "scum" on the top of the magma, Irving said.
NWA 7325 has a lower magnetic intensity — the magnetism passed from a cosmic body's magnetic field into a rock — than any other rock yet found, Irving said. Data sent back from NASA's Messenger spacecraft currently in orbit around Mercury shows that the planet's low magnetism closely resembles that found in NWA 7325, Irving said.
Messenger's observations also provided Irving with further evidence that could support his hypothesis. Scientists familiar with Mercury's geological and chemical composition think that the planet's surface is very low in iron. The meteorite is also low in iron, suggesting that wherever the rock came from, its parent body resembles Mercury.
While Messenger's first extended mission just finished, the team has put in a request to continue researching the planet with the orbiter for the next two years. If the mission is extended until 2015, the science returned by the spacecraft could help further validate or invalidate Irving's ideas about the origin of the meteorite.Although finding meteorites on Earth that came from Mercury is less likely than finding Martian meteorites, it could be possible, Irving said.

Source of Article : space.com

Grand Canyon View From Space Reveals Jaw-Dropping Scenery

A jagged scar etched in copper-colored rocks, the Colorado River's channel curls through one of the world's most scenic landscapes.
Draining seven states and two countries, the river is one of the Southwest's most important water sources. One of its major reservoirs, Lake Powell, can be seen from space in a photo snapped March 12 by an astronaut aboard the International Space Station.
Sunglint (reflected sunlight) gives the water a mirrorlike sheen, reports NASA's Earth Observatory. In the photo, the river runs left to right because the astronaut was looking at the river canyon from the south. North is to the bottom of the image.
An abandoned river meander, called The Rincon, stands out like a pimple at the left edge of the photo. The long, knife-sharp edge of the snow-dusted Straight Cliffs, a plateau in the Grand Staircase-Escalante National Monument, divides the middle. 
Though the Colorado River now cuts through rocks nearly 2 billion years old in the Grand Canyon, the river is only 50 million years old. Its waters headed to the southwest or the north of the current Grand Canyon — geologists disagree on the details — until about 5 million years ago.

Source of Article : space.com

2013년 3월 27일 수요일

Solar System's Mysterious Rock Origin Puzzle Revealed

Rocks melted in the early solar system after electrical currents spiked through the cloud of dust circling around the young sun, according to new research.
The finding brings scientists a step closer to understanding the origin of the chondrules, or glass beads, that were some of the solar system's first solids.
Because chondrules form far away from the sun, astronomers could not figure out how they heated to at least 2,420 degrees Fahrenheit (1,600 degrees Kelvin), since the surrounding environment is much colder, according to observations.

More mysteriously, the rocks apparently cooled within an hour or two after forming, instead of freezing instantly into a crystal, which would be expected in space.
"This was a puzzle, because quite a lot of material must have passed through this process," said Mordecai-Mark Mac Low, the chair of astrophysical sciences at the American Museum of Natural History in New York.
A typical early meteorite, called a chondrite, could be made up of 70 to 80 percent of this glassy material. "It's a large fraction of mass, even in regions far away from the sun where the sun can't [heat] it," said Mac Low, who is also an adjunct professor at Columbia University.
Mac Low co-authored a paper reporting the findings that was published in the March 20 edition of The Astrophysical Journal Letters.
Bound by magnetism
Chondrules are one of two types of solids that made up the early solar system. Chondrules are clumps of dust that heated up and cooled rapidly, while the second type of solid — calcium-aluminum rich inclusions (CAIs) — was created from molten gas droplets.
A separate study, based on dating techniques, recently proposed that chondrules and CAIs formed at the same timein Earth's solar system, just a few million years after the protoplanetary disc of spinning matter formed around the nascent sun.
This spinning disc of matter, Mac Low said, contained an enormous amount of kinetic energy. This was the biggest source of energy for disc motions. Differential rotation, and energy, increased the amount of kinetic energy in the disc as regions closer to the sun rotated faster than regions farther out.
Material was dragged on to the young sun through a process called magnetorotational instability. This occurs when a weak magnetic field runs through differentially rotating gas, connecting regions orbiting at different speeds. The turbulence mixed angular momentum outward, allowing the bulk of the gas to fall inward and accrete onto the sun.
"That appears to be one of the major mechanisms to drive accretion," Mac Low said, adding that it could even be applicable to black holes.
In the solar system, however, Mac Low's research team suspects magnetorotational instability may also fuel the formation of chondrules.
Fluorescent light bulb question
Magnetized turbulence bends magnetic fields, producing electrical currents. These currents travel through the resistive gas, heating it. This is the same process that allows heating to happen in toasters and electric ovens.
The bent magnetic fields in the disc form thin, flat regions of strong electrical current called "current sheets." The production of current sheets by magnetized turbulence has been known by plasma researchers since the 1970s, but Mac Low's team applied this understanding of current sheet formation to protoplanetary discs for the first time.
The question was, Mac Low said, how much the sheets heated the rocks.
"We might just get a fluorescent light bulb," he joked, adding that it seemed quite possible given most of the protoplanetary disc was made of neutral gas. At first glance, there were not a lot of ions, or charged particles, to carry the current.
Museum researcher Alexander Hubbard, co-author of the study, then came upon the answer. A little heating will start to excite the atoms that are easiest to ionize — namely, salty substances such as potassium and sodium.
Warming those substances will ionize them, which will increase the available current. With more ions in the current, the substances would heat even more and increase ionization exponentially.
"It looks like something that could get us up to the temperature we needed," Mac Low said.
Aiming for three dimensions
Next, the researchers tried to figure out why the chondrules cooled slowly in the cold reaches of space. Dust opacity, or thickness, changes with the temperature. As the dust melted, the highest temperature region formed a transparent cavity, surrounded by opaque material still warmed by radiation from the hottest gas.
"The newsworthy conclusion is that under conditions reasonable for protoplanetary discs, these regions can get plenty hot. Sometimes over 2,000 Kelvin (3,140 Fahrenheit), hot enough to melt rocks," Mac Low said.
So far, the researchers have simulated this process in only one dimension. The next step will be to move toward a three-dimensional model to better simulate conditions in the early solar system.
While the paper did not include new observations, Mac Low pointed out that Chile's Atacama Large Millimeter/submillimeter Array (ALMA) could, in time, partially confirm the findings.
"We won't be able to observe individual current sheets ... but ALMA will be able to tell us about dust grain size and distribution," he said of the telescope, which was officially inaugurated this month.
The research was led by Denmark's Niels Bohr International Academy and includes scientists from the American Museum of Natural History, Columbia University and the National Autonomous University of Mexico.

Source of Article : space.com

NASA 'Super Guppy' Swallows Supersonic NASA Jets

Two supersonic NASA jets were swallowed whole by the space agency's outsized Super Guppy Transport plane in California this month so that they could be ferried to Texas.
The pair of retired T-38 jets, which are no longer airworthy, were loaded into the Guppy on March 18 at NASA Dryden Flight Research Center in Edwards, Calif.,and flown to El Paso. The jets' parts will be cannibalized and used for other T-38s that are still flying.
The loading process, which took over two hours, involved opening the Guppy's nose and hoisting the T-38s onto a specially designed pallet that was put into the Guppy's 25-foot (7.6-meter) diameter "stomach" of the NASA Super Guppy aircraft. Only the T-38s' wingtips needing to be removed so that the jets could fit inside the carrier, Johnson Space Center flight engineer David Elliott, the Guppy's project manager, said in a statement.
The Super Guppy is the last in its class of wide-bodied aircraft to have transported NASA's unwieldy cargo to their launch site, including rockets for the Apollo program and room-size modules for the International Space Station. The plane is based at Ellington Airport in Houston, near NASA's Johnson Space Center.
The first Guppy aircraft, called the Pregnant Guppy, was built from a heavily modified KC-97 Stratotanker in 1962 by the California-based company Aero Spacelines. Its 19-foot (5.8-meter) diameter cargo compartment was the largest such cavity of any aircraft at the time and it was designed to hold the second stage of a Saturn rocket for the Apollo program.
The next generation, Dubbed the B377SG Super Guppy, was built in 1965 and was outfitted with a 25-foot (7.6-meter) diameter cargo bay, more powerful turboprop engines, a pressurized cockpit, and a hinged nose for easier loading of cargo, according to NASA.
The planes were operated by Aero Spacelines until NASA purchased the aircraft in 1981. The space agency still uses the Super Guppy Transport — the last generation of Guppy that Aero Spacelines built. The plane is slated to bring the Orion Heat Shield from Textron Defense Systems near Boston to NASA's Kennedy Space Center at the end of March. The U.S. Department of Defense and government contractors also have used the Guppy to ferry aircraft and large components around the continent.

Source of Article : space.com

New Theory of How Giant Stars Grow Unveiled

Baby stars can grow to an incredibly large size — 10 times more massive than the sun, at the least — if they are cocooned in a group of older stars feeding gas to the youngsters, a new study suggests.
This theory could explain how young stars get so big, rather than pushing away gas as they grow and starving themselves once they get about eight times as massive as the sun.
Researchers spotted evidence of this type of "convergent constructive feedback" with the Herschel Space Observatory. It took pictures of a large dust and gas cloud called Westerhout 3, located about 6,500 light-years from Earth, in wavelengths ranging from infrared to part of the microwave spectrum.
"This observation may lift the veil on the formation of the most massive stars, which remains, so far, poorly understood," said Alana Rivera-Ingraham, lead author of the study. She was at the University of Toronto when the research was performed, and is now a postdoctoral researcher at the Research Institute of Astrophysics and Planetology in France.

Star corral

Stars typically form in the midst of huge gas clouds. The force of gravity squeezes the gas until it is compressed enough to start the nuclear fusion process that fuels stars.
Newborn stars are constantly balancing two opposite forcesas they grow. Gravity sucks in gaseous material to feed the protostar, while radiation pressure emanating from the protostar resists the inward pull of gravity and pushes away some of the gas surrounding it.
The bigger a star gets, the greater the radiation pressure, until it reaches a point where the gas should — by conventional theory — be blown away.
The densest part of Westerhout 3's gas cloud, researchers noted, is enclosed by a crowd of older, large stars.
That thick environment is no coincidence, scientists said. Providing the older stars are in the right position — surrounding a gas reservoir — the gas they push away through radiation could compress and form new stars.
"The process is similar to the way a group of street cleaners armed with leaf blowers can stack leaves in a pile — by pushing from all sides at the same time," officials at the University of Toronto said in a statement. "This corralling of dense gas can give birth to new, high-mass stars."
The group still needs to test this theory through simulation, and by comparing observations of Westerhout 3 to those of similar stellar gas clouds.
"Only then will [scientists] be able to discern the mechanism — collective feeding or not — that gives rise to high-mass stars in these giant clouds," according to the statement.
Another solution proposed
In 2009, another group of researchers proposed a different way that stars can grow massive.
The group ran a three-dimensional simulation of how a large interstellar gas cloud falls into itself and creates a huge star. The computer showed instabilities where the radiation sent part of the cloud out into space, while gas continued to spiral in toward the star through other channels.
"This shows that you don't need any exotic mechanisms; massive stars can form through accretion processes just like low-mass stars," study leader Mark Krumholz of the University of California, Santa Cruz said in a 2009 interview.
Previous to that research, scientists believed radiation pressure would push away the gas surrounding a protostar before it could reach a mass 20 times that of the sun.
The theory, though, was contradicted by multiple observations of supermassive stars, which do exist but are rarer than small stars.

Source of Article : space.com

2013년 3월 25일 월요일

Jupiter's Moon Europa May Have 'Spikes of Ice'

The equator of Jupiter's icy moon Europa may be covered with huge spikes of ice, scientists say.
Astronomers have known for some time that Jupiter's moon Europa is icy, and now scientists are trying to understand just what form that ice takes by using some of the coldest places on Earth as analogues. Huge ice spikes, known as penitents, found on Earth could form on Europa, they said.
"It's a pretty obscure geological feature on the Earth," Dan Hobley, an astronomer at the University of Virginia, told  after he presented his findings at the 44th annual Lunar and Planetary Science Conference.
The 3.3 to 16.4 foot (1 to 5 meter) spikes of ice only grow in certain parts of the Andes mountains on Earth, but those areas of the world serve as good proxies for what Europa's geology might be like, Hobley said.
It takes a very specific set of circumstances for penitentes to form, Hobley said. The angle of the sun has to hit the ice in just the right way to keep the spikes of ice standing on end and buried deep into the ground. The blades grow in very dry conditions and can thrive in dirt-filled or clean circumstances.
As far as scientists can tell right now, all of those environments exist along Europa's equator, Hobley said.

Although Europa has been observed using radar and spectroscopy, scientists have not been able to understand exactly what the surface of this moon looks like. The geological features of Europa seem "basically random," Hobley said, but the existence of penitentes could offer an explanation.
Scientists have found that Europa's equator is warmer than it should be, and penitentes could explain that mysterious temperature, Hobley said. The ice spines reflect heat onto one another, creating a warmer area because the sunlight gets trapped bouncing from ice spike to ice spike, Hobley explained.
The scientist and his colleagues are interested in understanding what the surface of Europa looks like, partially because it's a first step towards designing a viable lander that could safely touch down on the moon's frozen surface.
But it might not be that simple, Hobley said.
The icy shell of Europa's surface might shift occasionally, displacing the area of the alien world that used to be its equator. Penitentes don't naturally form in higher latitudes, so if the shell does shift, that could create a problem for astronomers trying to map exactly where to set down a lander.
"We're at the state where this is a good, solid guess," Hobley said.

Source of Article : space.com

Fly Me to the Moon ... and Jupiter, Too (Photo)

A jet aircraft crosses the face of the moon while Jupiter and its own satellites Io, Calisto, and Europa share the spotlight in this stunning night sky photo.
Astrophotographer Greg Gibbs took this photo on Feb. 18 from a remote region in New South Wales, Australia. Gibbs used a 10-inch (250mm) F/4 Newtonian Telescope mounted on an NEQ6 Pro Telescope Mount and a Canon 60D camera to capture the image. The camera was hooked into the focuser of the telescope.
The shot is the result of two stages: First Gibbs took a continuous set of duration shots to make sure he had the plane, Jupiter and the moon all visible in a single image. 
Then Gibbs took a longer exposure to highlight three of the Jupiter's moons: Io, Calisto, and Europa. This rare conjunction lasted only a few moments and the moon will not eclipse Jupiter in the same way again until 2016.
"It was a good thing that I was on a deserted country road because my scream of excitement would have echoed for miles. I had managed to get the plane crossing the moon in five individual frames just as Jupiter was about to be occulted by the moon, as well as a further seven or so frames with the dissipating jet trail.  I knew right then that I had captured something unique," Gibbs wrote on his website, Capturing the Night.

Source of Article : space.com

2013년 3월 24일 일요일

Slumbering Sun Should Wake Up This Year

The sun should roar back to life sometime in 2013, producing its second activity peak in the last two years, scientists say.
Our star has been surprisingly quiet since unleashing a flurry of flares and other eruptions toward the end of 2011. But this lull is likely the trough between two peaks that together constitute "solar maximum" for the sun's current 11-year activity cycle, researchers say.
"If you look back in history, many of the previous solar cycles don't have one hump, one maximum, but in fact have two," solar physicist C. Alex Young, of NASA's Goddard Space Flight Center in Greenbelt, Md., said today (March 22) during a NASA webcast called "Solar MAX Storm Warning: Effects on the Solar System."
"That's what we think is going to happen," Young added. "So we've reached one of those humps, and we think that eventually activity will pick back up and we'll see another hump — a double-humped solar maximum."

Before the twin peaks scenario began to gain adherents, many researchers had predicted that solar maximum for the current cycle, known as Solar Cycle 24, would come this May. But given how quiet the sun is at the moment, the second hump will likely occur later than that, and it could last into 2014, scientists have said.
Saying the sun is quiet right now, however, does not mean that it's lifeless. Indeed, our star blasted out a huge cloud of superheated plasma known as a coronal mass ejection (CME) on March 15.
This CME delivered a glancing blow to Earth two days later, sparking a mild geomagnetic storm that had no serious effects. Powerful CMEs that hit Earth squarely can spawn serious such storms, temporarily knocking out power grids, GPS signals and radio communications.
But CME effects aren't all negative. They can also supercharge Earth's auroras, also known as the northern and southern lights, giving skywatchers around the world a treat.

Source of Article : space.com

Private SpaceX Cargo Capsule's Return to Earth Delayed One Day

A private cargo capsule's trip home to Earth from the International Space Station has been delayed by one day to Tuesday because of weather concerns near its targeted splashdown site.
SpaceX's unmanned Dragon spacecraft is now scheduled to splash down at 12:36 p.m. EDT (1636 GMT) on Tuesday (March 26) in the Pacific Ocean, 246 miles (396 kilometers) off the coast of Baja California, NASA officials announced Friday (March 22).
Dragon will be carrying about 2,670 pounds (1,210 kilograms) of equipment, hardware and scientific experiments, none of which should be affected by the slight delay, officials said.
"The additional day spent attached to the orbiting laboratory will not affect science samples scheduled to return aboard the spacecraft," NASA officials wrote in a Friday update.

Dragon launched toward the space station on March 1 and arrived two days later with about 1,200 pounds (544 kg) of supplies. The capsule's current mission is the second of 12 cargo deliveries California-based SpaceX is making under a $1.6 billion deal with NASA.
Dragon is slated to be released from the orbiting lab at 7:06 a.m. EDT (1106 GMT) on Tuesday. Its deorbit burn will take place 4 1/2 hours later, setting the stage for its Pacific Ocean splashdown. SpaceX personnel will retrieve the capsule with a crane-equipped boat and return it to shore about 30 hours later, NASA officials said.
SpaceX is one of two companies that hold a commercial cargo deal with NASA. The other is Virginia-based Orbital Sciences, which scored a $1.9 billion contract to make eight unmanned flights with its Antares rocket and Cygnus capsule.
Antares is slated to make its first test flight in the middle of April, and a demonstration mission to the space station should follow later this year if all goes well. Dragon, for its part, first visited the orbiting lab on a demonstration flight in May of last year and made its first contracted cargo run in October.

2013년 3월 21일 목요일

Apollo Moon Rocket Engines Raised from Seafloor by Amazon CEO

Long thought to be lost forever on the ocean floor, massive engines that launched astronauts to the moon more than 40 years ago have been recovered by a private expedition led by the founder of Amazon.com.
"We found so much," said Jeff Bezos, the online retailer's CEO, in an update posted Wednesday (March 20) on the Bezos Expeditions website. "We have seen an underwater wonderland – an incredible sculpture garden of twisted F-1 engines that tells the story of a fiery and violent end, one that serves testament to the Apollo program."
When NASA's mighty Saturn V rockets were launched on missions to Earth orbit and the moon in the late 1960s and early 1970s, the five F-1 engines that powered each of the boosters' first stages dropped into the Atlantic Ocean and sank to the seafloor. There they were expected to remain, discarded forever.
Then, almost exactly one year ago, Bezos announced his private — and until then, secret — expedition had located what they believed to be theengines from the 1969 Apollo 11 mission that began the journey to land the first humans on the moon.
"Nearly one year ago, Jeff Bezos shared with us his planes to recover F-1 engines," said NASA administrator Charles Bolden in a statement that was released Wednesday. "We share the excitement expressed by Jeff and his team in announcing the recovery of two of the powerful Saturn V first-stage engines from the bottom of the Atlantic Ocean."

Poetic echoes of lunar missions
When Bezos first revealed that his team had discovered the engines using state-of-the-art deep-sea sonar, he said he wasn't sure what condition they were in.
"They hit the ocean at high velocity and have been in salt water for more than 40 years. On the other hand, they are made of tough stuff, so we'll see," Bezos wrote in 2012.
What they saw, using Remotely Operated Vehicles (ROV), was a tangled pile of F-1 engine parts strewn across the ocean floor at a depth of more than 14,000 feet (4,270 meters).
"We photographed many beautiful objects in situ and have now recovered many prime pieces," Bezos wrote in the update Wednesday. "Each piece we bring on deck conjures for me the thousands of engineers who worked together back then to do what for all time had been thought surely impossible."
The scene also evoked the Apollo moon missions themselves.
"We on the team were often struck by poetic echoes of the lunar missions," Bezos wrote. "The buoyancy of the ROVs looks every bit like microgravity. The blackness of the horizon. The gray and colorless ocean floor. Only the occasional deep sea fish broke the illusion."
Bezos and his team are now heading back to port in Cape Canaveral, Fla., after working for three weeks at sea on the Seabed Worker, a multi-purpose support vessel.

Recovery, restoration and display
The Bezos expedition returned enough major components to rebuild two Saturn V F-1 engines— out of the 65 that were launched between 1967 and 1973 — for display. Despite claims last year that the engines were specifically from Apollo 11, Bezos now says the history of the engine parts he recovered may not be known.
Inspecting the raised pieces, Bezos reported that many of the parts' original serial numbers are missing or partially missing, which may make mission identification difficult.
"We might see more during restoration," Bezos wrote.
Once the engine parts are back on land, they will undergo a restoration to stabilize the hardware and prevent further corrosion from their decades-long exposure to the ocean's salt water. But Bezos hinted the restoration may not return the engines to like-new condition.
"We want the hardware to tell its true story, including its 5,000 mile per hour re-entry and subsequent impact with the ocean surface," Bezos stated. "We're excited to get this hardware on display where just maybe it will inspire something amazing."
Where the recovered F-1 engines will go on exhibit is still to be decided. Last year, Bezos expressed a desire that if two or more of the engines were successfully raised, one would go on display at The Museum of Flight in Seattle, near where Amazon and Bezos' commercial spaceflight company, Blue Origin, are headquarted.
NASA, which retains ownership of the engines and all of its parts, said it would likely offer one to the Smithsonian's National Air and Space Museum in Washington, DC.
"We look forward to the restoration of these engines by the Bezos team and applaud Jeff's desire to make these historic artifacts available for public display," Bolden said.

Source of Article : space.com

New Map of Big Bang Light Hints at Exotic Physics

Europe's Planck spacecraft has revealed the most detailed map yet of the earliest light in the universe, which reveals some tantalizing anomalies that could point toward new physics.
The new map tracks small temperature variations in the glow pervading space called the cosmic microwave background (CMB). This light was released just 380,000 years after the Big Bang, and contains a record of how our universe came to be.
By and large, the new data from Planck agree with cosmologists' leading ideas about how the universe formed. The theory of inflation suggests that after the Big Bang, the universe ballooned rapidly from its tiny, hot state, doubling in size every 10^-35 seconds (a decimal point followed by 34 zeroes and a one).
But where the basic models of inflation say this expansion should have happened uniformly in all directions, the new Planck results suggest that might not have been the case. 
"One of the features of inflation is it says there should be no preferred direction — everywhere in the universe should be more or less the same," astrophysicist Marc Kamionkowski of Johns Hopkins University said today (March 21) during a NASA press call. "But when you look at the amplitudes, even by eye you can tell that one side of the universe looks different from the other side."
That is to say, the temperature variations in the CMB appear to be sized and spaced differently when Planck looks in one direction, than when it looks in the other.
There are other anomalies as well. The variations don't appear to behave the same on large scales as they do on small scales, and there are some particularly large features, such as a hefty cold spot, that were not predicted by basic inflation models.
Ultimately, the data show "some features that are surprising and very, very intriguing," said Charles Lawrence, U.S. Planck project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
"Hopefully in the process of understanding those features better we will be able to glimpse answers to some of our deepest questions."
Indeed, the map's deviations from what was predicted are not cause for disappointment among scientists, but rather exhilaration. They could even lead toward unraveling the mysteries of dark matter and dark energy, two perplexing constituents of the universe that have yet to be explained by mainstream theories.
For example, the new CMB measurements produce a new estimate for the age and expansion rate of the universe, which the Planck scientists calculate to be 13.8 billion years old, and 41.73 miles (67.15 kilometers) per second per megaparsec, respectively. The expansion rate is also known as the Hubble constant, and the new estimate is significantly lower than the values derived through other astronomical observations.
"This is one of the most exciting parts of the data, is this apparent tension between these different ways to estimate how rapidly the universe is expanding," said Martin White, U.S. Planck scientist at the University of California, Berkeley. "The hope would be that this is actually pointing toward some deficiency in the models or some extra physics."
The expansion rate of the universe is deeply connected to the idea of dark energy, which is the name scientists have given to whatever is causing the universe's expansion to accelerate. The finding could point toward a new direction of thinking about dark energy, including the possibility that it has changed over time.
"If it was different than the simplest models, if the amount of dark energy was somehow increasing with time in a given volume of space, then that would alleviate some of the tension," White said, and added, "that's a pretty radical thing to propose."
And getting to the bottom of the other anomalies in the Planck data may point to even more radical conclusions, such as the idea of multiple universes and bubble universes created by areas of the primordial universe that inflated at different rates.
It turns out that collisions between these bubbles of space-time are one possible explanation for why inflation might not have proceeded uniformly in all directions.
"The fact that these anomalies not only exist but exist on the very largest scales gives us some hope that we may be actually able to say something in the future about a multiverse," Kamionkowski said.

Source of Article : space.com

2013년 3월 19일 화요일

Mystery of Vanishing Dwarf Galaxies Explained?

Some dwarf galaxies in the early universe travelled so fast that their gas was stripped from them, according to a new computer simulation.
This cosmic vanishing act could help explain a long-standing mystery: astronomers observe fewer dwarf galaxies in the "Local Group" — the collection of galaxies near the Milky Way — than what models of the universe's formation predict.
But if these galaxies are losing gas, that could explain why they don't appear as plentiful as they should.
Because these dwarf galaxies were so small when they formed, they don't have large reserves of gas to begin with. Stripping any gas away would leave these galaxies so small and dim that they would be all but invisible from Earth.
"This is something that came out of the simulations, and had not been anticipated, and had not been seen before. It was an interesting discovery," said Julio Navarro, a University of Victoria astronomer and co-author of a paper describing the discovery.
The study, published in the Feb. 1 issue of Astrophysical Journal Letters, was led by graduate studentAlejandro Benitez-Llambay from the University of Cordoba in Argentina.
Courting CLUES
Past supercomputer simulations show there should be a huge number of dwarf galaxies, together making up one one-thousandth of the Milky Way's mass, scattered around the local environment. But a 1999 study pointed out that the dwarf galaxies we see are not representative of the calculated mass.
In the past, astronomers suggested that the energy from supernovas, as well as ultraviolet rays permeating the universe, might alter the dwarf galaxies as they form. There were weaknesses with these models, however. Observed supernova energy is too low to affect dwarf galaxy formation, and the ultraviolet rays only shrink the smallest of dwarf galaxies.
To better examine the issue, the new study focused on how dwarf galaxies evolved in the early stages of the universe. Astronomers ran a simulation tracking dark matter halos that duplicate the positions of the three largest galaxies in the Local Group: the Milky Way, Andromeda (M31) and Triangulum (M33).
Next, they re-ran the simulation to focus on one small area in much higher resolution. This allowed them to examine dwarf galaxy evolution in detail.
"We constrained and controlled the numbers to resemble our local environment," Navarro said.
The tool they used was called Constrained Local UniversE Simulations, or CLUES for short. The project, led by the Leibniz Institute for Astrophysics, can simulate the positions and speeds of galaxies within 10 million light years of the Milky Way.

Passing the cosmic speed limit
CLUES revealed that the farthest dwarf galaxies in the Local Group are flying very quickly through the cosmic web of dark matter and ordinary matter that makes up our universe.
When the galaxies pass a given speed, the ram pressure between the dwarf galaxies and this cosmic web strips the galaxies' gas away. It's similar to how the matter gets stripped away from a meteor as it rams through the Earth's atmosphere.
"The galaxy moves at high speed, and the gas strips out and stays behind the galaxy," said Stefan Gottlöber, a Leibniz astronomer who leads CLUES. He was also a co-author on the new paper.
While the gas is all but invisible, we might be able to see the effects gas stripping has had on the galaxies. The astronomers noted that dwarf galaxies are a diverse bunch, with some looking like gas clouds and others filled with stars. Gas stripping could explain why star formation stopped, the scientists suggested.
Navarro, Gottloeber and their collaborators plan another run with CLUES to simulate a larger area to test whether the dwarf galaxy stripping in the Local Group is representative of the entire universe.

Source of Article : space.com

2013년 3월 14일 목요일

Confirmed! Newfound Particle Is the Higgs

A newfound particle discovered at the world's largest atom smasher last year is, indeed, the Higgs boson, the particle thought to give other matter its mass, scientists reported today (March 14) at the annual Rencontres de Moriond conference in Italy.
Physicists announced on July 4, 2012, that, with more than 99 percent certainty, they had found a new elementary particle weighing about 126 times the mass of the proton that was likely the long-sought Higgs boson. The Higgs is sometimes referred to as the "God particle," to the chargrin of many scientists, who prefer its official name.
But the two experiments, CMS and ATLAS, hadn't collected enough data to say the particle was, for sure, the Higgs boson, the last undiscovered piece of the puzzle predicted by the Standard Model, the reigning theory of particle physics.
Now, after collecting two and a half times more data inside the Large Hadron Collider (LHC) — where protons zip at near light-speed around the 17-mile-long (27 kilometer) underground ring beneath Switzerland and France — physicists say the particle is the Higgs.
"The preliminary results with the full 2012 data set are magnificent and to me it is clear that we are dealing with a Higgs boson though we still have a long way to go to know what kind of Higgs boson it is," said CMS spokesperson Joe Incandela in a statement.

Dave Charlton, ATLAS spokesperson agreed, the new results "point to the new particle having the spin-parity of a Higgs boson as in the Standard Model," referring to a quantum property of elementary particles.
To confirm the particle as the Higgs boson, physicists needed to collect tons of data that would reveal its quantum properties as well as how it interacted with other particles. For instance, a Higgs particle should have no spin and its parity, or the measure of how its mirror image behaves, should be positive, both of which were supported by data from the ATLAS and CMS experiments.
Even so, the scientists are not sure whether this Higgs boson is the one predicted by the Standard Model or perhaps the lightest of several bosons predicted to exist by other theories.
Seeing how this particle decays into other particles could let physicists know whether this Higgs is the "plain vanilla" Standard Model Higgs. Detecting a Higgs boson is rare, with just one observed for every 1 trillion proton-proton collisions. As such, the LHC physicists say they need much more data to understand all of the ways in which the Higgs decays.
From what is known about the particle now, physicists have said the Higgs boson may spell the universe's doom in the very far future. That's because the mass of the Higgs boson is a critical part of a calculation that portends the future of space and time. Its mass of 126 times the mass of the proton is just about what would be needed to create a fundamentally unstable universe that would lead to a cataclysm billions of years from now.
"This calculation tells you that many tens of billions of years from now there'll be a catastrophe," Joseph Lykken, a theoretical physicist at the Fermi National Accelerator Laboratory in Batavia, Ill., said last month at the annual meeting of the American Association for the Advancement of Science.
"It may be the universe we live in is inherently unstable, and at some point billions of years from now it's all going to get wiped out," added Lykken, a collaborator on the CMS experiment.

Source of Article : space.com

Giant Alien Planet in Supersized Solar System May Solve Mystery

The glowing atmosphere of a strangely giant alien world could help solve mysteries of not just how it formed, but how our own solar system arose, scientists say.
The exoplanet discovery comes from the most detailed look yet at the allien planets around the distant star HR 8799, which lies about 130 light-years from Earth. The HR 8799 system is home to four giant planets orbiting a relatively young, 30-million-year-old star, with each planet far larger than any world found in Earth's solar system.
The planets orbiting HR 8799 weigh in at between five to 10 times the mass of Jupiter and are still glowing with the heat of their formation, allowing researchers to directly image them.
"It's the only system in which multiple planets can individually be seen," said study co-author Bruce Macintosh, an astronomer at Lawrence Livermore National Laboratory in California.
The planetary system resembles a scaled-up version of our solar system, suggesting there may be smaller Earth-size planets closer in, although the researchers currently have not yet seen any.
It even "has something that kind of looks like maybe an asteroid belt interior to the closest giant planet like we have in our solar system, and something that maybe you can refer to as an Oort cloud analog out beyond the most distant gas giant" — that is, a cloud of icy comets, said study lead author Quinn Konopacky, an astronomer at the University of Toronto.
Exoplanet's atmosphere revealed
The astronomers concentrated on one of the star's visible planets, named HR 8799c, a colossal gas giant about seven times the mass of Jupiter. It circles the star HR 8799 at a range comparable to Pluto's distance from the sun.
The birth of such a massive planet at such a great distance from its parent star conflicts with the two popular models of planetary formation. In the multistep process known as core accretion, gas slowly accumulates onto a planetary core, while the mechanism known as gravitational instability involves the simultaneous creation of a planet's interior and atmosphere.
"In the traditional core accretion model of planet formation, it is difficult to form planets as large as the HR 8799 planets at such large distances from their parent star," Konopacky told SPACE.com. "Typically, in this model, objects the size of Jupiter or larger must form much closer to their parent star. This is for several reasons, but has a lot to do with there being less material at large distances from the star that can form planets."
"In the gravitational instability method of formation, it is possible to form big planets at large distances, usually because they invoke a much more massive disc of material," Konopacky added. "But the model generally predicts that there should be many more massive objects orbiting lots of other stars at these distances, and these kinds of objects have not been discovered in surveys [of many stars for exoplanets].
To help solve this mystery, the scientists analyzed the glow from HR 8799c using a high-resolution imaging spectrograph called OSIRIS at the Keck Observatory in Hawaii. Molecules in atmospheres can absorb light, resulting in patterns known as spectra that allow scientists to identify what they are.
HR8799c is both fairly bright and located a fair distance from its star, helping the researchers acquire this spectral data for the most detailed examination yet of the atmosphere of a Jupiter-like planet beyond the solar system.
"The most exciting part of this result is that we were able to make these observations of an exoplanet atmosphere with this level of detail, much more than I even imagined was possible," Konopacky said. "We have broken the light from the planet down to such a fine level of detail that the chemical fingerprints of the molecules in the atmosphere are breathtakingly sharp and distinct. This is important because it requires data of this quality to truly probe the makeup of a planetary atmosphere, and in turn, say something about how the planet formed."
Missing methane: a clue
The scientists detected water and carbon monoxide in the exoplanet's atmosphere, but not methane.
The lack of methane "tells us that there must be mixing between the different layers of the atmosphere, much like a lava lamp swirls material up and down," Konopacky said. "Since methane is a sensitive molecule, it can be destroyed when it gets mixed into the deeper, hotter parts of the atmosphere. This mixing tells us about the atmospheric conditions in young Jupiter-like planets."
In addition, although the researchers see a lot of water vapor in the atmosphere of HR 8799c, "we actually detect slightly less than we would have expected if the planet had the same composition as its host star," Konopacky said. "This tells us that the planet has a slightly elevated amount of carbon compared to oxygen." 
This high ratio of carbon to oxygen is a clue regarding the exoplanet's formation. The researchers suggest that grains of water ice condensed in the disc of matter surrounding HR 8799 that gave rise to the planets orbiting the star. Oxygen inside the ice depleted any other oxygen for the formation of HR 8799c.
"These ice grains stuck together to make bigger ice chunks, a few kilometers across, that kept colliding and building up the planet's solid core," Konopacky said. "The atmosphere came later — from gas that the planet attracted after it got big enough. By the time that happened, some of the ice grains were gone and the gas didn't have as much water in it."
How planets are born
These findings imply that a planet-building mechanism known as core accretion led to the formation of HR 8799c, "much in the same way we think the planets in our own solar system formed," Konopacky said. The exoplanet's core arose first, and the atmosphere came afterward.
"These results represent a first step in finding direct evidence about how planets form, which in general, is a difficult thing to do observationally," Konopacky said. "It is really exciting that we have these tantalizing suggestions that this extrasolar system that looks like our own solar system in so many ways may have formed in the same way."
Researchers are now tinkering with existing models of core accretion to see how planets might form via the process at great distances from their stars. For instance, there may be more matter at the outer edges of the protoplanetary discs of matter around stars that give rise to planets than before thought, or perhaps solid matter could stick together and form planetary cores easier or faster than previously suspected.
"By further refining the core accretion model of formation to explain the HR 8799 planets, we may be able to learn more about the formation of planetary systems in general, including our own solar system," Konopacky said.
"We would also like to discover more planets through direct imaging that can be studied at this level of detail," Konopacky added. "We work on a new instrument called the Gemini Planet Imager that is designed to do just this. It will arrive at the Gemini South Telescope in Chile this year, and discover new planets that are both smaller than the HR 8799 planets and closer to their parent star."
Konopacky and her colleagues Travis Barman, Bruce Macintosh and Christian Marois detailed their findings online March 14 in the journal Science.

Source of Article : space.com

2013년 3월 9일 토요일

Alien Moons Could Host Life Outside 'Habitable Edge'

Astronomers have their fingers crossed that within the haul of data collected by NASA's Kepler mission, which has already detected nearly 3,000 possible exoplanets, hide the signatures of the very first exomoons. 
The discovery of alien moons will open up an exciting new frontier in the continuing hunt for habitable worlds outside the solar system. With the confirmation of exomoons likely right around the corner, researchers have begun addressing the unique and un-Earthly factors that might affect their habitability.
Because exomoons orbit a larger planetary body, they have an additional set of constraints on their potential livability than exoplanets themselves. Examples include eclipses by their host planet, as well as reflected sunlight and heat emissions. Most of all, gravitationally induced tidal heating by a host planet can dramatically impact a moon's climate and geology.
In essence, compared to planets, exomoons have additional sources of energy that can alter their "energy budgets," which, if too high, can turn a temperate, potential paradise into a scorched wasteland.
"What discriminates the habitability of a satellite from the habitability of a planet in general is that it has different contributions to its energy budget," said René Heller, a postdoctoral research associate at the Leibniz Institute for Astrophysics in Potsdam, Germany.

The 'habitable edge'
In a series of recent papers, Heller and his colleague Rory Barnes from the University of Washington and the NASA Astrobiology Institute tackled some of the big-picture problems to habitability posed by the relationship between exomoons and their host planets.
Heller and Barnes have proposed a circumplanetary "habitable edge," similar to the well-established circumstellar "habitable zone." This zone is the temperature band around a star within which water neither boils off nor freezes away on a planet's surface — not too hot, not too cold, thus earning it the nickname "the Goldilocks zone."
The habitable edge is rather different. It is defined as the innermost circumplanetary orbit in which an exomoon will not undergo what is known as a runaway greenhouse effect. "To be habitable, moons must orbit their planets outside of the habitable edge," Heller said.
A runaway greenhouse effect occurs when a planet’s or moon's climate warms inexorably due to positive feedback loops. This phenomenon is thought to have taken place on Earth's so-called "sister planet," Venus.
On Venus, the heat from a young, brightening sun could have increasingly evaporated a primordial ocean. This evaporative process put ever more heat-trapping water vapor in the atmosphere, which led to more evaporation, and so on, eventually drying the planet out as the water was broken apart into hydrogen and oxygen by the sun's ultraviolet radiation. The atmospheric hydrogen on Venus escaped into space, and without hydrogen, no more water could form. 
Moons situated in fairly distant orbits from their planets should be safely beyond the habitable edge wherein this desiccation takes place.
"Typically, and especially in the solar system, stellar illumination is by far the greatest source of energy on a moon," Heller said. "In wide planetary orbits, moons will be fed almost entirely by stellar input. But if a satellite orbits its host planet very closely, then the planet's stellar reflection, its own thermal emission, eclipses and tidal heating in the moon can become substantial."
The cumulative effects of the non-tidal heating effects are small, but could be the difference between an exomoon being inside or outside the habitable edge.

Basking in the glow
Here on Earth, we get a little extra energy from the moon in the form of moonlight, which is reflected light from the sun.
Moons, though, get bathed in a lot more sunlight from their planetary neighbors; Earth shines almost 50 times as brightly in the lunar sky as the moon does in our night sky. In addition to reflected sunlight, planets also emit absorbed sunlight as thermal radiation onto their exomoons.
This "planetshine" can add a not-insubstantial amount of energy to an exomoon's overall intake. Imagine a gas giant planet orbiting a sun-like star at about the same distance that Earth orbits our sun. For a moon with a relatively close orbit around this planet, like Io’s orbit around Jupiter, Heller calculates that the moon could absorb an additional seven or so watts per square meter of power. (Earth absorbs about 240 watts per square meter from the sun).
Periodic plunges into darkness
Eclipses can potentially offset some of the extra energy input from planetshine. For eclipses, Heller calculated that lost stellar illumination for an exomoon in a close orbit (similar to the closest found in our solar system) is up to 6.4 percent.
Interestingly, because most moons (including ours) are tidally locked to their planet — that is, one side of the moon constantly faces the planet — eclipses, as well as planetshine, would only darken and lighten one hemisphere. This phenomenon could modify the climate, as well as the behavior of life forms, in ways not seen on Earth. 
"Asymmetric illumination on the moon could induce wind and temperature patterns, both in terms of geography and in time, which are unknown from planetary climates," Heller noted. "Life on a moon with regular, frequent eclipses would surely have to adapt their sleep-wake and hunt-hide rhythms as well, but only those creatures on the planet-facing hemisphere."
Roll tides
Although the eclipse-related loss of several percentage points of illumination is not a huge loss of energy, a moon-planet duo might need to be closer to its star to compensate for this deficit if the moon were still to be considered habitable from a Goldilocks zone perspective.
However, this situation introduces another hurdle to habitability: The closer a planet is to its star, the stronger the star's gravitational pull is on the planet's moons. This extra pull can tug moons into non-circular, or eccentric, orbitsabout their planets. Eccentric orbits, in turn, result in varying amounts of gravitational stress exerted on the moon as it orbits.
These “tidal forces,” as they are called, cause heating due to friction. The ocean tides we experience on Earth occur partly as a result of the moon's gravity tugging more on the water and land nearest it, which distorts Earth's shape. The effect goes both ways, of course, but not equally, with planets inducing significantly greater tidal heating within their much smaller moons.
If an exomoon's orbit takes it too close to its planet, tidal heating could push the energy budget too high, culminating in a runaway greenhouse effect. At the extremes, the tidal heating could unleash massive volcanic activity, leaving the satellite covered in magma and distinctly inhospitable, like the "pizza moon".
On the other hand, it should be noted, tidal heating might be a savior for life. Tidal heating could help sustain a subsurface ocean, like the one suspected to exist within Jupiter's moon Europa, alternatively making an otherwise unwelcoming exomoon outside the traditional habitable zone potentially livable.

Small stars, dead moons
Another factor comes into play as eclipses rob a bit of energy from an exomoon and require the moon-planet pair to be closer to their star. To remain gravitationally bound to a planet and not be ripped away by the star's gravity, a moon must fall within a so-called “Hill radius” — the planet's sphere of gravitational dominance. This radius shrinks with greater proximity to the host star. The closer the planet and moon are to their star, the less space is available outside the habitable edge.
For planets and attendant moons around dim, cool, low-mass stars called red dwarfs, this dynamic becomes important. The habitable zone around red dwarf stars is very tight; for a star with a quarter of the sun's mass, for instance, the Goldilocks zone is thought to be around just 13 percent the sun-Earth distance – in other words, a third of Mercury's orbital distance from the sun. 
In a red dwarf solar system, not only must a moon then be closer to its habitable zone planet, but given the planet's necessary proximity to its star, the moon's orbit will tend to be eccentric. These qualities increase the chances that the moon will fall within the habitable edge.
Heller calculated that for many red dwarf stars, the odds of them hosting habitable moons is accordingly slim.
"There is a critical stellar mass limit below which no habitable moon can exist," Heller said. "Around low-mass stars with masses of about 20 percent the mass of the sun, a moon must be so close to its habitable zone planet to remain gravitationally bound that it is subject to intense tidal heating and cannot under any circumstances be habitable."

A little here, a little there
Many factors beyond habitable edge considerations, of course, ultimately determine an exomoon's habitability.
To be considered broadly habitable by creatures other than, say, subsurface bacteria, an exomoon must meet some of the same basic criteria as a habitable, Earth-like exoplanet: It must have liquid surface water, a long-lived substantial atmosphere and a magnetic field to protect it from solar radiation (and, in the case of exomoons around gas giants like Jupiter, from the charged particles created in the giant exoplanet's magnetosphere).
To possess these qualities, which scientists say grow likelier with increasing mass, a habitable exomoon will likely be quite large compared to those in the solar system – more on the order of the size of Earth itself. The biggest moon in our solar system, Jupiter's Ganymede, is just 2.5 percent of Earth's mass. But previous studies have suggested that monstrous moons by the solar system's standards are indeed possible.
NASA's Kepler mission is expected to be able to detect exomoons down to about 20 percent of the mass of the Earth. The data, which consists of measuring the extremely small dips in the amount of starlight as their planets (or moons) block it from our point of view – should reveal a moon’s mass and orbital parameters as well.
Armed with this information — and now with habitable edge considerations — astronomers can thus hope to make some ballpark speculations on any soon-to-be-discovered exomoon’s propensity to support living beings.
Heller hopes that there will be a list of candidate exomoons ready for observing by next-generation instruments, such as NASA's James Webb Space Telescope and various 30-meter-class ground telescopes. These observatories, coming online in the next decade, could be able to characterize exomoon atmospheres and offer tantalizing evidence of life.
"The first exomoons that we find will be large — maybe Mars- or even Earth-sized — and therefore intrinsically more likely to be habitable than small moons," Heller said. "With Kepler finding many more giant planets than terrestrial planets in stellar habitable zones, it's really important that we try to figure out what conditions might be like on the moons of these giants to gauge if they can host extraterrestrial life." 

Source of Article : space.com