By Alexis Madrigal
The first genetically modified primates that can pass their modifications to their offpsring have been created by Japanese scientists.
The marmosets, pictured above, express a green fluorescent protein in their skin. The gene for producing the glow was delivered to the first marmoset embryos via a modified virus. But now that modification method could become unnecessary. One male marmoset, number 666, fathered a child (pictured at right) that also contained the transgenes.
“The birth of this transgenic marmoset baby is undoubtedly a milestone,” developmental biologists Gerald Schatten and Shoukhrat Mitalipov at the Pittsburgh Development Center and Oregon Stem Cell Center, respectively wrote in a commentary accompanying the study Thursday in Nature. “The cumbersome and often frustrating process of making a transgenic animal from scratch need now only occur with founder animals.”
Transgenic animals are a key tool in the biomedical researchers’ toolbox. They allow scientists to model the function of genes and the efficacy of treatments. Many transgenic mice lines exist, but often the small rodents are too different from humans to effectively extrapolate their responses to human beings. Primates, on the other hand, are far closer biologically to humans, but before the new technique, creating primate models had proven difficult and expensive.
Now, biologists may be able to produce whole groups of marmosets that mimic humans with genetic diseases like cystic fibrosis.
“Subsequent generations can be produced by natural propagation, with the eventual establishment of transgene-specific monkey colonies — a potentially invaluable resource for studying incurable human disorders, and one that may also contribute to preserving endangered primate species,” Schatten and Shoukhrat continued.
Instead of using bonobos or chimps, the research team led by Erika Sasaki at the Central Institute for Experimental Animals in Japan picked the common marmoset because its “size, availability, and unique biological characteristics” make it a potentially useful animal, particularly in tough fields like neuroscience and stem cell research.
Thursday, May 28, 2009
Tuesday, May 26, 2009
Federal Reserve Cannot Account for $9 Trillion
By: Julie Crawshaw
The Federal Reserve apparently can't account for $9 trillion in off-balance sheet transactions.
When Rep. Alan Grayson (D-Orlando) asked Inspector General Elizabeth Coleman of the Federal Reserve some very basic questions about where the trillions of dollars that have come from the Fed's expanded balance sheet, the IG didn't know.
Worse, nobody at the Fed seems to have any idea what the losses on its $2 trillion portfolio really are.
"I am shocked to find out that nobody at the Federal Reserve is keeping track of anything," Grayson says.
Grayson asked Coleman if her agency had done any research into the decision not to save Lehman Brothers, which “sent shockwaves through the entire financial system,” Coleman said it had not.
“What about the $1 trillion plus expansion of the Federal reserve’s balance sheet since last September?” Grayson asked.
“We have different connotations,” Coleman replied. “We’re actually conducting a fairly high-level review of the various lending facilities collectively.”
Translation: Nobody at the Fed knows where the money went.
Do you know what who got the $1 trillion or more in the Fed's expansion of its balance, Grayson pressed.
"I do not know. We have not looked at this specific area at the particular point on that specific review," Coleman answer.
What about the trillions of off-balance transactions since last September, Grayson asked.
Coleman demurred again, saying the IG does not have jurisdiction to audit the Federal Reserve.
Grayson pointed out that it was the inspector general's job to audit such spending and asked again if the office had done any investigation at all.
Coleman's answer: Not enough yet to even respond. "We are in not a position to say if there losses."
Grayson concluded, "I am shocked to find out that nobody at the Federal Reserve, including the inspector general, is keeping track of this."
Meanwhile, Federal Reserve Chairman Ben Bernanke says the bank is working on ways to rein in the massive balance sheet commitments.
"A majority of the members who made these projections just recently took 2 percent as being an appropriate number" for inflation, Bernanke said Monday.
"Somewhere between 1-1/2 to 2 percent is basically the number that our committee has individually stated is the appropriate medium-term inflation rate.
"To achieve that we need to demonstrate that we will be able to exit from the balance sheet position that we currently have, and have been working on this intensively," Bernanke said in response to questions after a speech to a conference organized by the Federal Reserve Bank of Atlanta, reported by Reuters.
The Federal Reserve apparently can't account for $9 trillion in off-balance sheet transactions.
When Rep. Alan Grayson (D-Orlando) asked Inspector General Elizabeth Coleman of the Federal Reserve some very basic questions about where the trillions of dollars that have come from the Fed's expanded balance sheet, the IG didn't know.
Worse, nobody at the Fed seems to have any idea what the losses on its $2 trillion portfolio really are.
"I am shocked to find out that nobody at the Federal Reserve is keeping track of anything," Grayson says.
Grayson asked Coleman if her agency had done any research into the decision not to save Lehman Brothers, which “sent shockwaves through the entire financial system,” Coleman said it had not.
“What about the $1 trillion plus expansion of the Federal reserve’s balance sheet since last September?” Grayson asked.
“We have different connotations,” Coleman replied. “We’re actually conducting a fairly high-level review of the various lending facilities collectively.”
Translation: Nobody at the Fed knows where the money went.
Do you know what who got the $1 trillion or more in the Fed's expansion of its balance, Grayson pressed.
"I do not know. We have not looked at this specific area at the particular point on that specific review," Coleman answer.
What about the trillions of off-balance transactions since last September, Grayson asked.
Coleman demurred again, saying the IG does not have jurisdiction to audit the Federal Reserve.
Grayson pointed out that it was the inspector general's job to audit such spending and asked again if the office had done any investigation at all.
Coleman's answer: Not enough yet to even respond. "We are in not a position to say if there losses."
Grayson concluded, "I am shocked to find out that nobody at the Federal Reserve, including the inspector general, is keeping track of this."
Meanwhile, Federal Reserve Chairman Ben Bernanke says the bank is working on ways to rein in the massive balance sheet commitments.
"A majority of the members who made these projections just recently took 2 percent as being an appropriate number" for inflation, Bernanke said Monday.
"Somewhere between 1-1/2 to 2 percent is basically the number that our committee has individually stated is the appropriate medium-term inflation rate.
"To achieve that we need to demonstrate that we will be able to exit from the balance sheet position that we currently have, and have been working on this intensively," Bernanke said in response to questions after a speech to a conference organized by the Federal Reserve Bank of Atlanta, reported by Reuters.
Friday, May 22, 2009
Wednesday, May 20, 2009
Good News, Short People: Your Senses May Be Faster Than Tall People’s
By Discovermagizine.com
Short people may be disadvantaged on the basketball court, in the workplace, and when trying to see over large crowds, but they just might be quicker in sensing the world around them—because, well, their signals don’t have to travel as far to get to their brains.
In effect, this means that tall people are living in the past, if only by a tenth of a second. This is all according to neuroscientist David Eagleman, whose essay entitled “Brain Time” suggests that “if the brain wants to get events correct timewise, it may have only one choice: wait for the slowest information to arrive.”
See, before the brain can process external events, it must receive and synchronize all incoming sensory data—from the eyes, ears, tongue, and skin. But these messages come at different times and speeds. For example, if someone touches your nose and your foot at the same time, you register the touches simultaneously, even though the signals had to travel farther from your foot to your brain than they did from your nose.
As such, according to Eagleman, the brain may wait for the last signal to arrive before it processes what a group of signals mean. Because sensory signals need more time to travel the longer limbs of tall people, he says, their brains could experience a (very very small) processing delay.
The average tall person, therefore, “will live his sensory life on a teeny delay.” Though it’s still not enough to make short people superior at basketball. With the occasional exception.
Short people may be disadvantaged on the basketball court, in the workplace, and when trying to see over large crowds, but they just might be quicker in sensing the world around them—because, well, their signals don’t have to travel as far to get to their brains.
In effect, this means that tall people are living in the past, if only by a tenth of a second. This is all according to neuroscientist David Eagleman, whose essay entitled “Brain Time” suggests that “if the brain wants to get events correct timewise, it may have only one choice: wait for the slowest information to arrive.”
See, before the brain can process external events, it must receive and synchronize all incoming sensory data—from the eyes, ears, tongue, and skin. But these messages come at different times and speeds. For example, if someone touches your nose and your foot at the same time, you register the touches simultaneously, even though the signals had to travel farther from your foot to your brain than they did from your nose.
As such, according to Eagleman, the brain may wait for the last signal to arrive before it processes what a group of signals mean. Because sensory signals need more time to travel the longer limbs of tall people, he says, their brains could experience a (very very small) processing delay.
The average tall person, therefore, “will live his sensory life on a teeny delay.” Though it’s still not enough to make short people superior at basketball. With the occasional exception.
Monday, May 18, 2009
Is Everything Made of Mini Black Holes?
Written by Nancy Atkinson
In 1971 physicist Stephen Hawking suggested that there might be “mini” black holes all around us that were created by the Big Bang. The violence of the rapid expansion following the beginning of the Universe could have squeezed concentrations of matter to form miniscule black holes, so small they can’t even be seen in a regular microscope. But what if these mini black holes were everywhere, and in fact, what if they make up the fabric of the universe? A new paper from two researchers in California proposes this idea.
Black holes are regions of space where gravity is so strong that not even light can escape, and are usually thought of as large areas of space, such as the supermassive black holes at the center of galaxies. No observational evidence of mini-black holes exists but, in principle, they could be present throughout the Universe.
Since black holes have gravity, they also have mass. But with mini black holes, the gravity would be weak. However, many physicists have assumed that even on the tiniest scale, the Planck scale, gravity regains its strength.
Experiments at the Large Hadron Collider are aimed at detecting mini black holes, but suffer from not knowing exactly how a reduced-Planck-mass black hole would behave, say Donald Coyne from UC Santa Cruz (now deceased) and D. C. Cheng from the Almaden Research Center near San Jose.
String theory also proposes that gravity plays a stronger role in higher dimensional space, but it is only in our four dimensional space that gravity appears weak.
Since these dimensions become important only on the Planck scale, it’s at that level that gravity re-asserts itself. And if that’s the case, then mini-black holes become a possibility, say the two researchers.
They looked at what properties black holes might have at such a small scale, and determined they could be quite varied.
Black holes lose energy and shrink in size as they do so, eventually vanishing, or evaporating. But this is a very slow process and only the smallest back holes will have had time to significantly evaporate over the enter 14 billion year history of the universe.
The quantization of space on this level means that mini-black holes could turn up at all kinds of energy levels. They predict the existence of huge numbers of black hole particles at different energy levels. And these black holes might be so common that perhaps “All particles may be varying forms of stabilized black holes.”
“At first glance the scenario … seems bizarre, but it is not,” Coyne and Cheng write. “This is exactly what would be expected if an evaporating black hole leaves a remnant consistent with quantum mechanics… This would put a whole new light on the process of evaporation of large black holes, which might then appear no different in principle from the correlated decays of elementary particles.”
They say their research need more experimentation. This may come from the LHC, which could begin to probe the energies at which these kinds of black holes will be produced.
In 1971 physicist Stephen Hawking suggested that there might be “mini” black holes all around us that were created by the Big Bang. The violence of the rapid expansion following the beginning of the Universe could have squeezed concentrations of matter to form miniscule black holes, so small they can’t even be seen in a regular microscope. But what if these mini black holes were everywhere, and in fact, what if they make up the fabric of the universe? A new paper from two researchers in California proposes this idea.
Black holes are regions of space where gravity is so strong that not even light can escape, and are usually thought of as large areas of space, such as the supermassive black holes at the center of galaxies. No observational evidence of mini-black holes exists but, in principle, they could be present throughout the Universe.
Since black holes have gravity, they also have mass. But with mini black holes, the gravity would be weak. However, many physicists have assumed that even on the tiniest scale, the Planck scale, gravity regains its strength.
Experiments at the Large Hadron Collider are aimed at detecting mini black holes, but suffer from not knowing exactly how a reduced-Planck-mass black hole would behave, say Donald Coyne from UC Santa Cruz (now deceased) and D. C. Cheng from the Almaden Research Center near San Jose.
String theory also proposes that gravity plays a stronger role in higher dimensional space, but it is only in our four dimensional space that gravity appears weak.
Since these dimensions become important only on the Planck scale, it’s at that level that gravity re-asserts itself. And if that’s the case, then mini-black holes become a possibility, say the two researchers.
They looked at what properties black holes might have at such a small scale, and determined they could be quite varied.
Black holes lose energy and shrink in size as they do so, eventually vanishing, or evaporating. But this is a very slow process and only the smallest back holes will have had time to significantly evaporate over the enter 14 billion year history of the universe.
The quantization of space on this level means that mini-black holes could turn up at all kinds of energy levels. They predict the existence of huge numbers of black hole particles at different energy levels. And these black holes might be so common that perhaps “All particles may be varying forms of stabilized black holes.”
“At first glance the scenario … seems bizarre, but it is not,” Coyne and Cheng write. “This is exactly what would be expected if an evaporating black hole leaves a remnant consistent with quantum mechanics… This would put a whole new light on the process of evaporation of large black holes, which might then appear no different in principle from the correlated decays of elementary particles.”
They say their research need more experimentation. This may come from the LHC, which could begin to probe the energies at which these kinds of black holes will be produced.
Friday, May 15, 2009
China Grapples With Bigger Role in New World Order, Zhou Says
By Kevin Hamlin at Bloomberg.com
China’s policy makers, grappling with their bigger voice on the global stage, have yet to agree on what they want from a new world financial order, central bank Governor Zhou Xiaochuan said.
“Many issues are new to us and we haven’t formed a collective opinion about them,” said Zhou, speaking at a conference in Shanghai today. “There are some scholars’ views on those issues but we haven’t reached a consensus at a national level or set any goal.”
Zhou this year has already called for the creation of a new international reserve currency and his central bank blamed the financial crisis on “complacency” and a conviction in the U.S. that markets always correct themselves. China, the only major economy among the top five globally that is still growing, wants the International Monetary Fund reorganized to give developing countries more voice.
“In the past China only dealt with internal adjustments needed to take advantage of opportunities in the world,” said Shanghai-based Andy Xie, former chief Asia economist for Morgan Stanley. “Now China faces the challenge of participating in reorganizing the world. That’s never happened before.”
China needs to think carefully about what it wants, what it stands for, and how it will participate in a remaking of the global financial order, Zhou said.
High-Profile Role
China’s fallen into its higher-profile role on the global stage as a consequence of the global crisis and it’s not prepared,’’ said Dwyfor Evans, a strategist with State Street Global Markets in Hong Kong. “Zhou’s saying to policy makers: ‘We need a coherent global strategy rather than the unilateral strategy we’ve had in the past.’”
The central bank’s research arm in March said that “market forces, if unchecked, will lead to asset bubbles and ultimately a disastrous market clearing in the form of a financial crisis like the current one.”
A lack of coordination among regulatory agencies and communication between regulators and central bankers and finance ministers in some advanced countries hampered efforts to manage the financial crisis, the research arm said.
Zhou said that the global financial crisis can’t be resolved by the G-7 alone and added that emerging economies need to have more involvement in working out solutions.
-With assistance" for Li Yanping in Shanghai. Editors: David Tweed, Russell Ward
To contact the reporter on this story: Kevin Hamlin in Beijing at khamlin@bloomberg.net
Wednesday, May 13, 2009
The genomes of 50 HIV-resistant people may open new doors to understanding disease
By Kendall Morgan at insciences.com
Durham, NC -- In the 1970s and 1980s, before safety measures were in place to screen out tainted blood, people with hemophilia were routinely exposed to HIV-infected blood products. Most of those patients became infected and later died of AIDS, but a significant minority – some 20 percent of those who were almost certainly exposed to the virus repeatedly – did not.
Now, David Goldstein, director of the IGSP’s Center for Human Genome Variation, and his colleagues think that the complete genome sequences of those fortunate few will be key in the search for rare genetic variants that offer significant protection from HIV. Indeed, such host resistance to HIV is uncommon, existing in only a small percentage of the general population. It has been traced, in part, to the presence of genetic variants linked to the ability to block infection.
“But these known variants explain only a very small amount of the differences among individuals exposed to the HIV virus,” says Goldstein. “We think there are probably other, much rarer variants that also play a role. We just haven't had the right setting or tools to find them. But now we do,” supported by a $3 million grant from the Bill & Melinda Gates Foundation.
Goldstein’s group will sequence the full genomes of 50 HIV-resistant people with hemophilia whose ability to ward of the infection can’t be explained by previously identified protective gene variants.
As of mid-December, they had already completed the first of those genomes at a moderate level of coverage. Given that other efforts to sequence human genomes to date have focused on sampling “normal” individuals representing different geographical regions, that first sequence is notable in and of itself; it will become the first complete “human disease genome” known to science, IGSP Associate Investigator Kevin Shianna says. Ultimately, they expect to churn out all 50 complete human genome sequences over a period of six months, a feat made possible by seven next-generation sequencing machines known as Illumina Genome Analyzers.
“One way to look at it is that we will be generating the equivalent of a Human Genome Project every week,” Goldstein said. “We’re gearing up now to produce data in volumes that are absolutely unprecedented.”
A Deluge of Data
That quantity of data presents major challenges. With genome-wide association studies (GWAS), there are a fixed number of possible variations researchers can always rely on, and even that can be overwhelming because there are millions of them.
That’s where Goldstein team member Dongliang Ge, now a new IGSP faculty member, enters the picture. Ge developed software called Sequence Variant Analyzer to sort out the absolute overload of information to come from the new whole-genome sequencing studies.
The data coming from the next-generation sequencing machines in the Genome Analysis Facility that Shianna runs will enter a streamlined pipeline for analysis, Ge explains.
The Analyzer will filter through variants in search of those with potential functional relevance, automatically assigning each to one of 16 possible categories. For instance, it will determine which changes alter the makeup of a protein or which insert a “stop” in a location that would cause complete loss of a protein or even which might lead to changes in other functional entities in the genome. They’ll also be able to detect immediately which variations have been seen before and which are unique. Researchers interested in particular pathways, such as those important to the functioning of the immune system, can easily filter the variation to find the relevant bits.
“We think we can catch just about anything we know about,” Ge says.
Goldstein agrees, adding that the new tool essentially encapsulates the “theory of everything. It takes everything we know about the human genome to find those variants with potential functional relevance.”
Eventually, they’ll narrow the list of contenders down by comparing the 50 HIV-resistant genomes to one another and to control sequence from participants in the 1000 Genomes Project, an international effort designed to create the most detailed picture so far of human genome variation by sequencing 1,000 individuals from all over the world.
The Case of the Missing Heritability
The ongoing study is just the beginning of a broader effort by Goldstein’s team to investigate what is still a very new idea: that even common diseases are caused in large part by rare changes in the genome. The idea has arisen from the realization that previous studies of common disease have turned up disappointingly little in the way of common genetic causes.
“There have now been comprehensive screens for common variants for most common diseases, and I believe we’ve gotten out most of what’s to be had,” Goldstein says. “We are left with a dark matter problem. If you assess heritability, it’s high for everything. Then you look at common variation and we’re missing a lot of the genetic control. It could be some other phenomenon masquerading as heritability, but I think it’s relatively rare and highly penetrant things that are now missed.”
In support of such a notion, a recent report in Science, which included Goldstein as a collaborator, found new genetic variants associated with schizophrenia, all of which are rare deletions or duplications in the genome.
The approach the IGSP team is taking now in HIV resistance – sequencing the complete genomes of people with extreme characteristics – may be the best way to find such rare and elusive genetic variants. Shianna said they also plan to do a whole-genome sequencing study of people with schizophrenia who are resistant to treatment. They have plans on the horizon to sequence people at the extremes of cognition, including a group with well-documented “photographic” memories, meaning that they have essentially perfect recall of everything that has ever happened to them. And, in the HIV realm, Goldstein’s group will also sequence people at another extreme: those who immediately progress to AIDS almost as soon as they become infected with HIV.
This new approach to genomics will no doubt be an important tool in many cases, says Greg Wray, director of the IGSP’s Center for Evolutionary Genomics and overseer of the IGSP’s core DNA sequencing facility. But it won’t necessarily apply in all instances.
“For some diseases, the rare stuff will be critical,” Wray says. “Given the costs, the big challenge will be to determine which diseases are best approached from this perspective. In some cases GWAS or microarrays that measure gene expression may be all we need to know. There are a growing number of approaches and no one will be right in every case.”
While Goldstein agrees, he and his team are confident that the new approach will soon lead them to new HIV-resistance variants. And though few people may carry them, those variants could prove to have incredible significance for many more individuals.
“We hope this project will yield new information that will help us to further understand disease resistance and to identify new targets and guidance for drug and vaccine development," says Goldstein. "Rare human genetic variation is a new frontier for discovery.”
Tuesday, May 12, 2009
A Scientist's Guide to Finding Alien Life: Where, When, and in What Universe
By Adam Frank at Discovermagazine.com
Things were not looking so good for alien life in 1976, after the Viking I spacecraft landed on Mars, stretched out its robotic arm, and gathered up a fist-size pile of red dirt for chemical testing. Results from the probe’s built-in lab were anything but encouraging. There were no clear signs of biological activity, and the pictures Viking beamed back showed a bleak, frozen desert world, backing up that grim assessment. It appeared that our best hope for finding life on another planet had blown away like dust in a Martian windstorm.
What a difference 33 years makes. Back then, Mars seemed the only remotely plausible place beyond Earth where biology could have taken root. Today our conception of life in the universe is being turned on its head as scientists are finding a whole lot of inviting real estate out there. As a result, they are beginning to think not in terms of single places to look for life but in terms of “habitable zones”—maps of the myriad places where living things could conceivably thrive beyond Earth. Such abodes of life may lie on other planets and moons throughout our galaxy, throughout the universe, and even beyond.
The pace of progress is staggering. Just last November new studies of Saturn’s moon Enceladus strengthened the case for a reservoir of warm water buried beneath its craggy surface. Nobody had ever thought of this roughly 300-mile-wide icy satellite as anything special—until the Cassini spacecraft witnessed geysers of water vapor blowing out from its surface. Now Enceladus joins Jupiter’s moon Europa on the growing list of unlikely solar system locales that seem to harbor liquid water and, in principle, the ingredients for life.
Astronomers are also closing in on a possibly huge number of Earth-like worlds around other stars. Since the mid-1990s they have already identified roughly 340 extrasolar planets. Most of these are massive gaseous bodies, but the latest searches are turning up ever-smaller worlds. Two months ago the European satellite Corot spotted an extrasolar planet less than twice the diameter of Earth (see “The Inspiring Boom in Super-Earths”), and NASA’s new Kepler probe is poised to start searching for genuine analogues of Earth later this year. Meanwhile, recent discoveries show that microorganisms are much hardier than we thought, meaning that even planets that are not terribly Earth-like might still be suited to biology.
Together, these findings indicate that Mars was only the first step of the search, not the last. The habitable zones of the cosmos are vast, it seems, and they may be teeming with life.
The Solar System Habitable Zone
One of the guiding tenets in the search for life as we know it (the only kind we can meaningfully speculate about) is that it requires water. Until recently, that rule led scientists to think only in terms of places just like home: temperate, rocky planets with bodies of liquid water on their surfaces. From there it was a simple matter to calculate where such worlds could exist within our solar system.
“If you define a habitable zone in terms of favorable climate, you get a pretty narrow band of orbits around the sun,” says Greg Laughlin of the University of California at Santa Cruz. “You can move the Earth inward toward the sun a couple of percent or move it outward by at most about 30 percent before the climate runs into a serious problem.” From this perspective, there is no other promising location for life in our solar system. Even if many other stars have solar systems too, planets that happen to orbit in just the right place to support life could be pretty rare.
That would be a depressing end to the story of habitable zones, if not for a series of amazing findings that life on Earth is not what everyone thought it was. “No one really expected it,” says Chris McKay, one of the pioneers of astrobiology—the hybrid field that studies how life could arise and evolve elsewhere in the universe. “People found strains of bacteria that don’t use food from the surface, don’t use oxygen from the surface, and don’t use sunlight from the surface.”
These newly revealed life-forms, called extremophiles, thrive in conditions so harsh a biologist 50 years ago would not have dreamed it possible. Giant tube worms, crabs, and shrimp live in the dark, a mile below the ocean surface, huddled around superheated geothermal vents. These vents are known as black smokers for the plumes of dark hydrogen sulfide they belch into the ocean. The organisms around them survive off chemicals from the vents in an ecosystem that operates without photosynthesis.
To McKay, these creatures are not the most exciting types of extremophiles, however. “They still rely on oxygen that is indirectly created by sunlight,” he says. Far more compelling are the bacteria that have been found thriving deep underground. One type lives five miles deep in the bowels of South African gold mines. “These creatures get their energy from sources we never imagined,” McKay exclaims. “The South African extremophile bacteria are powered by the radioactive decay of unstable atoms in the rocks. Sunlight and surface water play no role. It’s amazing!”
Extremophiles feeding on nonsolar energy sources show how alien life might similarly arise and thrive deep underground, far from surface water and sunlight. “Habitable planets don’t need to be like Earth,” McKay says. “That realization has driven the biggest expansion in our understanding of habitable zones.”
By happy coincidence, the discovery of extremophiles coincided with new studies showing that the solar system might have many previously unexpected warm, wet locations. In the 1990s the Galileo space probe collected convincing evidence that Jupiter’s large moon Europa has a global ocean of liquid water beneath its frozen surface. (NASA just announced plans to return there in 2027 to get a better look.) The recent discovery of the geysers on Enceladus added a second twist, making planetary scientists wonder if there are even more such hot spots scattered around the solar system. These locations lack sunlight and access to the surface—but apparently some kinds of life do nicely without either.
“When you take the discovery of liquid water below the surface of Europa and Enceladus and put it together with our understanding of terrestrial extremophiles,” McKay says, “you can see why the definition of ‘habitable zone’ had to change.”
The Galactic Habitable Zone
Astrobiologists’ new, grander view of habitability gets even more expansive when they look out to the galaxy around us. The Milky Way contains perhaps 200 billion stars. Now that we know a significant fraction of stars have planets, that number translates into (as Carl Sagan might say) billions and billions of worlds. Red dwarf stars, which are by far the most common stars in our galaxy, were once considered unlikely places to find Earth-like planets, but new studies contradict that view. And the extremophiles tell us that life could potentially take hold even on planets not much like our own.
All of that is the good news. But things are not quite so simple, because galaxies—like solar systems—have habitability zones of their own. Not all parts of a galaxy are suited to life. In 2004 astrobiologist Charley Lineweaver of Australian National University published a paper that broadly mapped out our galaxy, the Milky Way, with an eye toward possibilities and dangers for alien biology. In this case, the crucial factor is not the presence of water; it is the proximity of violent, massive stars.
The galaxy’s brightest, hottest, heaviest stars turn out to be crucial for both planets and biology. They are the universe’s only source of crucial heavy elements like silicon (which makes up more than a quarter of Earth’s crust), potassium (essential for the action of cells), and iron (which carries oxygen in our blood). These elements are forged in the stars’ fiery nuclear furnaces. Massive stars end their lives with supernova explosions that spray the heavy elements into space, where they are incorporated into the next generation of stars and help seed the formation of planets.
In thinking about the galactic habitable zone, Lineweaver made the presence of heavy elements his prime criterion. The rate at which massive stars form drops sharply as you venture outward from the Milky Way’s center, and the abundance of heavy elements falls with them. Lineweaver calculates that when the sun formed 4 billion years ago, the outer third of the galaxy lacked enough heavy elements to support life. Since then the elements have become more widely distributed, and now only the galaxy’s outer rim is too undernourished to form Earths easily. Our location, about two-thirds of the way toward the Milky Way’s stellar rim, lies at the center of the currently life-friendly region of the galaxy; the inner part of the galaxy turns out to be hostile to life too.
Massive stars give, but they also take away—and that puts the inner limit on the galactic habitable zone. The supernova explosions that create and spread heavy elements also unleash a torrent of high-energy radiation: gamma rays, X-rays, and ultraviolet light. Those stellar explosions can have lethal effects on planets orbiting stars even tens of light-years away. In the crowded central regions of the galaxy, home to large numbers of massive stars, supernovas are so common that the evolution of complex life-forms might be difficult if not impossible.
The big question is how bad the supernova effect is. Lineweaver and his colleagues calculate that radiation poisoning could exclude the inner 20 percent of the Milky Way, which encompasses about half of all the stars in the galaxy. “You are looking for that sweet spot,” says Fred Adams of the University of Michigan, “where you are not so close to the center that conditions are hostile and not so far out that the metal abundance is too low.” But the Milky Way is huge, so Adams suggests putting things in perspective. “At worst the amount of galactic real estate favorable to life is reduced by a factor of two or three,” he says.
The amount of real estate that is off-limits depends heavily on how life responds to strong doses of radiation. Remarkably, we may already have good information about that locked away in the fossil record right here on Earth.
Every 62 million years, something bad happens to Earth’s biodiversity,” says Adrian Melott of the University of Kansas. “Paleontologists have built up large data sets of all the animals in the fossil record. With these data you can look to see how biodiversity changed with time.” His provocative studies, backed by the work of other groups, show that drops in biodiversity—sometimes indicating mass extinctions—seem to follow a periodic cycle.
Melott links the changes in biodiversity to the motion of the sun and planets through our galaxy. “As the sun orbits the Milky Way, it also bobs up and down, rising above the plane of the disk and then diving below it,” he says. “Every time the sun rises up and pokes out of the ‘north’ side of the galaxy’s disk, our biodiversity goes way, way down.” He notes that the Milky Way’s north side points toward the Virgo cluster, an enormous nearby gathering of galaxies. Our galaxy (and, by extension, our planet and ourselves) is falling toward Virgo at about 120 miles per second.
According to Melott, as the Milky Way plows through intergalactic material, a powerful shock wave forms ahead of it. Shock waves create energetic subatomic particles called cosmic rays, which can tear apart biomolecules and damage DNA beyond repair. Normally the galaxy’s magnetic fields protect us from that radiation. Every 62 million years, though, the sun bobs up above the disk into the danger zone, Melott finds. “When the sun pokes up above the galaxy’s plane on the north side,” he says, “the entire planet gets a giant dose of cosmic rays.”
All stars follow a similar bobbing motion as they move through the galaxy, but ones in the inner regions do so at a faster pace, which may bolster Lineweaver’s view that those regions are less likely to contain complex life. Then again, a certain amount of radiation is a part of life—in fact, an essential part. Radiation helps drive mutation, and mass extinctions clear the way for evolutionary change. That view tends to bolster Adams’s optimistic outlook. “We want enough radiation to pose a challenge and spur development of new life-forms but not so much as to sterilize the whole planet,” Melott concludes.
The Temporal Habitable Zone
Melott’s hypothesis about mass extinctions shows how habitable zones may be measured not just in space but also in time. It turns out that “when” is just as important as “where” for the existence of life.
Supernovas come into play here, too. When the universe emerged from the Big Bang, it consisted almost entirely of hydrogen and helium. Good luck trying to make a planet, much less a person, out of that. Carbon, oxygen, iron, and the like had to wait for stars—especially the massive ones—to form and create heavier elements via nuclear fusion. Those processed elements escaped in stellar winds or supernova explosions and then got picked up by subsequent generations of stars. Building up the elements needed for life this way takes billions of years. The entire universe was, therefore, a nonhabitable zone for perhaps the first few billion years of its 13.7-billion-year history.
Once the universe is full of heavy elements, the tables turn and the mortal nature of stars becomes a limitation. The sun, a medium-size star, is about halfway into its total lifetime of 10 billion years. In another 5 billion years it will swell into a red giant and either consume our planet or bake its surface to concrete. Even sooner, in as little as a billion years, the sun’s gradually increasing luminosity may make Earth unbearable for life. Brighter, more massive stars, which guzzle their nuclear fuel more quickly, may burn out too quickly to allow complex life to evolve.
Fortunately, the realization that dim red dwarf stars could potentially support Earth-like planets greatly stretches out the temporal habitable zone. The dimmest, most economical of those stars might live 10 trillion years, a thousand times as long as the sun. Then again, current studies suggest that the universe will probably expand forever. If so, the cosmos as we know it—full of stars and, maybe, full of life—will be a fleeting moment in an endless duration of cold, dark nothingness.
Feeling grim again? Don’t worry; the latest physics theories point to yet another habitable zone that would allow life to go on long after the last star has expired.
The Multiverse Habitable Zone
These days, the largest habitable domain to consider is no longer our universe but the hypothetical universe of universes, what cosmologists call the multiverse. After our universe has gone black, perhaps another (or many others) will carry on life’s flame.
The idea that our universe—everything we can observe, including the laws of physics that shape it—is just one among a vast ensemble may seem the stuff of science fiction, but cosmologists build multiverse models using a theory called inflation. Inflationary cosmology, currently the dominant model of the early universe, holds that the entire observable cosmos began as a speck within a far larger (perhaps infinite) existence emerging from the Big Bang. Within 10-30 second after the moment of creation, this speck underwent a period of hyper-rapid expansion—hence “inflation”—becoming everything we see today. As bizarre as this model sounds, it has some reasonable observational support.
Some cosmologists go further and argue that inflation could also happen in other places and at other times, when these other bits of creation break out, undergo their own inflation, and become separate pocket universes. Physicists call this multiplication of reality “eternal inflation.” It leads to an almost limitless number of separate universes, each with its own laws of physics. (This dovetails with the equally weird predictions from string theory, a model of fundamental physics that suggests there could be something like 10500 different sets of laws.) “In some of these universes the force of gravity might be stronger or weaker than our own,” Fred Adams says. “In others the electromagnetic force that controls atoms and molecules could be different. The consequences for the formation of life in these different kinds of universes might be dramatic.”
Although there is no evidence for these multiverses, that has not stopped theorists from speculating about them. In our universe the laws of physics seem precisely calibrated to allow the existence of long-lived stars, planets with stable orbits, and molecules that allow complex chemistry. All of these seem to be prerequisites for life. “One of the things people always ask about is the behavior of stars in alternate universes,” Adams says. “If you have universes where stars can’t form, then it’s likely those would be pretty sterile places.”
Adams took this question seriously and began a study of alternative physics and its effect on the existence of stars. “I decided to do an actual calculation,” he says. “Could I get all this speculation down to a well-posed problem?” Each of the four fundamental forces (gravity, electromagnetism, and the strong and weak nuclear forces) has a kind of theoretical knob that can be turned up or down to change its strength. “I decided to calculate a bunch of theoretical stellar models, looking to see what range of forces gave me working stars,” Adams continues. The results surprised a lot of people.
“Many people claim that only a minute fraction of bubble universes would have the right conditions to harbor life,” Adams says. His calculations found instead that functioning stars would be more resilient to variations in physics than anyone expected. Since stars are a prerequisite for life, the findings could indicate far more possibilities for viable habitats. Fully a quarter of his models led to long-lived stars, but with an important caveat. Adams cannot say how probable any given strength of gravity or electromagnetism would be in a randomly chosen pocket. “What you need is to fold what I have done into a probability distribution across the multiverse,” he says. In other words, we need to know the statistics of variation in the laws of physics of pocket universes—and in inflationary cosmology there is no principle that guides the choice of physics in each of them.
Lee Smolin, a theoretical physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, has a controversial idea that makes some testable predictions about those other universes. In the process, he makes the case for habitability look even better than Adams inferred.
During the early 1990s Smolin proposed a multiverse model that differs strongly from inflationary cosmology’s pocket universes. His model focuses on the way that black holes warp space and time. Since the 1960s some theorists have floated the idea that when a massive star collapses into a black hole, it gives rise to a new universe. Smolin is building on that concept.
Black-hole-generated universes differ from the ones associated with eternal inflation in an important regard. With inflation there is no connection between the physics of one universe and that of another. The black-hole model, Smolin argues, strongly trends to certain types of physics. “Any universe that produces more black holes will create more daughter universes,” he says, “and its physics will be passed on to those daughters.” As a result, there should be a process analogous to natural selection favoring universes whose physics leads to the formation of more black holes. Such universes should dominate the multiverse.
Smolin’s model has two notable advantages. First, it explains why our universe has the physical laws that it does, since universes like ours that can create the massive stars that produce black holes are strongly selected. Second, it explains why our physical laws allow life to exist: The elements that permit the existence of stars happen to be the same ones that allow the existence of our kind of biology.
Actually, there is a third advantage. Smolin claims his black-hole multiverse hypothesis can be tested. Since universes that give rise to the largest number of black holes have the most offspring, our universe should be optimal for making black holes. Smolin’s predictions, including ideas about cosmological inflation and the mass of the heaviest stable neutron star, have held up so far. “The theory is falsifiable,” he says. “If observations come out contrary to my predictions, then the idea is wrong.”
But if Smolin is correct, we inhabit not just a universe but an entire multiverse that may be teeming with life—a habitable zone unbound.
See Adam Frank's recent book, The Constant Fire: Beyond the Science vs. Religion Debate, and the companion blog to the book.
Monday, May 11, 2009
Hubble Photographs Giant Eye in Space
The Hubble Space Telescope's legendary Wide Field and Planetary Camera 2 has produced one of its last images, a gorgeous shot of a planetary nebula.
The nebula, a colorful cloud of gas and dust named Kohoutek 4-55 (or K 4-55), has an eye that appears to be looking right back at Hubble.
The image was taken May 4 and released today.
Monday, NASA aims to send the space shuttle Atlantis to Hubble, where astronauts will replace the camera with the Wide Field Camera 3, among other upgrades and fix-it projects.
At a press conference today, space agency officials said the camera will make one last image tomorrow, of a nearby galaxy named IC 5152, but that image won't be released immediately.
Planetary nebulas have nothing to do with planets. They were named so because in early telescopes, they had the fuzzy look of planets in our outer solar system. In fact planetary nebulas sit throughout our galaxy. This one contains the outer layers of a red giant star that were expelled into space as the star entered its death throes.
Ultraviolet radiation from the remaining hot core of the star zaps the ejected gas shells, making them glow. A bright inner ring is surrounded by a bipolar structure. The entire system is then surrounded by a faint red halo, seen in the emission by lit-up nitrogen gas. This multi-shell structure is fairly uncommon in planetary nebulas, astronomers said.
The Wide Field and Planetary Camera 2 instrument, the size of a baby grand piano, was installed in 1993 to replace the original Wide Field/Planetary Camera. Among its iconic images:
- Eagle Nebula's "pillars of creation."
- Comet P/Shoemaker-Levy 9's impacts on Jupiter's atmosphere.
- The 1995 Hubble Deep Field – the longest and deepest Hubble optical image of its time.
The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. Images are processed at the Space Telescope Science Institute, which conducts Hubble science operations.
Friday, May 8, 2009
Lynyrd Skynyrd Bassist Dies
Ean Evans, the bassist for Lynyrd Skynyrd, has died after a long battle with cancer.
It's the second death in the storied band this year. In January, Billy Powell, the former keyboardist, also died.
In 1977 three band members died in a plane crash.
It's the second death in the storied band this year. In January, Billy Powell, the former keyboardist, also died.
In 1977 three band members died in a plane crash.
Thursday, May 7, 2009
Dark matter signal recedes into the shadows
From NewScientist.com
Dark matter seems to be receding further into the shadows. Last year, researchers thought they may have spotted its signature when a balloon-borne experiment called ATIC detected a bizarre spike in the number of high-energy electrons streaming in from space.
But now, NASA's Fermi space telescope finds no such spike – only subtle hints of a slight increase, suggesting that dark matter is not leaving any obvious trace in the charged particles detected from space.
Nobody knows exactly what dark matter is, but the leading theoretical model posits that it is made of up of particles called WIMPs (weakly interacting massive particles). When two WIMPS collide, the theory says, they annihilate, producing radiation and a cascade of particles, including electrons.
So researchers were excited last November, when a team studying data from two ATIC balloon flights over Antarctica reported finding many more electrons than expected at high energies around 600 gigaelectronvolts. Less exotic objects, such as pulsars and supernova remnants, also accelerate charged particles to high energies, so the ATIC data could potentially be explained by such garden-variety fare.
But the abundance and high energies of the 'extra' electrons detected, coupled with another unexpected cosmic ray result measured a few months earlier by a satellite called PAMELA, raised the tantalising possibility that dark matter – perhaps of an exotic type – might be responsible.
"Particle physicists have not had much to get excited about in the last 10 years – they were all ready for the Large Hadron Collider and then had a big setback" when it broke down, says Douglas Finkbeiner, a dark matter theorist at the Harvard-Smithsonian Center for Astrophysics. "Then PAMELA and ATIC came along with extra high-energy signals that could not be easily explained, and it was fun to think about."
Now, however, astrophysicists using the Fermi telescope say they don't see a dramatic spike in the number of high-energy electrons in space. "Our energy spectrum doesn't have prominent features," says Alexander Moiseev, a Fermi team leader at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Pros and cons
What could explain the discrepancy? For one thing, the two experiments have different strengths and weaknesses.
ATIC flew in Earth's atmosphere, which can create extra "noise" in its signal, while Fermi is a space mission. ATIC's balloon flights also lasted for no more than three weeks, while Fermi is constantly taking data from orbit.
Indeed, the Fermi team analysed more than 4 million high-energy electrons detected with the telescope over the course of about six months to arrive at their result, collecting hundreds of times more data at these energies than any previous measurement. "We are practically free of statistical errors," Moiseev told New Scientist.
But ATIC has a thicker calorimeter, an instrument at the bottom of its detector that incoming space particles strike, generating showers of other particles. "The deeper or thicker that calorimeter is, the less of that shower energy sneaks out the bottom," says ATIC team leader John Wefel of Louisiana State University in Baton Rouge.
"They can contain 68% of the energy, and we contain 85% of the energy," Wefel told New Scientist. As a result, he says there is more uncertainty in Fermi's measurement of the energy of incoming particles, which could broaden out any dramatic spikes like the one seen by ATIC.
"The reason they're not seeing that peak structure is because they have much poorer energy resolution in their instrument," says Wefel. He adds that his team has analysed a third balloon flight since the original ATIC announcement in November and finds the same sharp peak as before.
Instrumental effect?
The Fermi team acknowledges that it has a thinner calorimeter but says its detector is better in other ways – it boasts an instrument that tracks the path of incoming particles, for example – something that ATIC does not have. It has also run detailed computer algorithms that show its energy resolution is sharp enough to be able to see a spike in energetic electrons. "We would see an ATIC-like bump with huge confidence if it were there," maintains Moiseev.
Gregory Tarle, a physicist at the University of Michigan who is not affiliated with either team, agrees. The bump seen by ATIC "was probably an instrumental effect they hadn't compensated for", he says.
Both experiments have to grapple with the same basic challenge, Tarle explains – distinguishing between electrons and the much more abundant protons that pass through their detectors from space. Since neither experiment uses a magnetic field that could tell the two kinds of charged particles apart, the teams must try to do this by analysing the characteristics of the particle showers in their detectors.
"It's hard to make these measurements – very hard," says Tarle. But he says Fermi's calorimeter is better suited for the analysis than ATIC's. It is made of atoms that have a higher number of protons, which do not readily interact with protons coming in from space. That causes "less contamination in the electron
So if the ATIC bump isn't real, what does that mean for dark matter?
Tarle says it means that high-energy electron detectors such as ATIC and Fermi do not show any evidence for dark matter. "There's nothing in their data that could indicate new physics," he says.
But other researchers say Fermi's data does show what may be a subtle sign of dark matter. If they look at the data in the most conservative way, Fermi team members do not see this potential signature – they say the electron energy spectrum they measure is smooth, without any wiggles that might indicate 'extra' electrons.
If they are not as conservative, however, Fermi team members say they see a slight bump in the number of electrons at higher energies – though nothing as dramatic as ATIC's.
That gentle bump, they say, might be due to a slight theoretical underestimation of how many high-energy cosmic rays are produced in objects such as pulsars – an idea Tarle favours.
"The most likely explanation of the excess electrons at high energy seen by Fermi is that the theoretical estimates are wrong," Tarle says. "There is no reason to believe that these theoretical predictions based on lower energy data are valid in the high-energy regime of Fermi."
'Hard to fit'
Alternatively, it might be due to one or more nearby sources that are pumping out energetic electrons. The sources are thought to be nearby because high-energy electrons lose energy as they travel through space, so for them to arrive at the energies that Fermi detects, they must have come from somewhere within about 3000 light years of Earth.
The nearby sources could be pulsars, but "dark matter is not ruled out" as a possible source, says Moiseev.
Finkbeiner agrees. Last year, he and colleagues came up with a new model of dark matter that could account for both the PAMELA and ATIC signals.
After the Fermi team released its results at a physics meeting earlier this week, Finkbeiner said his inbox was flooded with emails saying, "So, annihilating dark matter is dead, right?" he says. "Nothing could be further from the truth."
"It was always a little bit hard to fit the ATIC bump," he says, explaining that such a sharp spike hints that dark matter might be annihilating straight to electrons – a process that is theoretically forbidden.
'Less information'
His and other dark matter models instead argue that annihilating dark matter particles create intermediate particles – such as pions – before producing electrons.
"It's hard to make a sharp feature but easy to make a broad, smooth feature" like the one Fermi may be seeing, he says, adding that the same is true for electrons produced in astrophysical sources such as pulsars.
"In a way, it's a relief we don't have to make the ATIC bump, but if ATIC is real, it would really be telling us something," Finkbeiner told New Scientist. "We're not likely to learn as much about dark matter from [Fermi's electron spectrum] – basically, we have less information than we had before."
Tricky observation
If further observations with Fermi suggest there is not even a gentle rise in the number of high-energy electrons it detects, that will make any annihilating dark matter difficult to observe – but it will necessarily not rule it out, says Finkbeiner.
"Before the ATIC and PAMELA results, the expected annihilation signal for the leading dark matter candidate, the WIMP, was much smaller, so failure to find a signal with Fermi does not in any way rule out conventional WIMP annihilation," he says.
"Of course, there could be no signal at all: dark matter could just sit there and gravitate and do absolutely nothing else," he adds. "That's kind of the most boring scenario: we can never learn what kind of particle it is."
Tracing the source
The Fermi team hopes to shed light on the issue by continuing to collect electron data from all over the sky. It's difficult to trace the source of electrons that fall into its detector because the charged particles are diverted by magnetic fields in space. But if Fermi detects even a slight excess of electrons in one region of the sky, it might point to their source, says Moiseev.
Fermi is also hunting for possible signs of dark matter in the distribution of gamma-ray photons in the sky. Gamma rays are thought to be produced by annihilating dark matter and unlike electrons, are not affected by intervening magnetic fields (see Where will new Fermi telescope find dark matter?).
Future experiments might also provide a cross-check of both ATIC and Fermi. One, called the Alpha Magnetic Spectrometer, may fly to the International Space Station before the shuttles are retired in 2010. It uses a magnetic field to separate charged particles and has a calorimeter a little thicker than Fermi's.
Journal reference: Physical Review Letters (vol 102, p 181101)
Dark matter seems to be receding further into the shadows. Last year, researchers thought they may have spotted its signature when a balloon-borne experiment called ATIC detected a bizarre spike in the number of high-energy electrons streaming in from space.
But now, NASA's Fermi space telescope finds no such spike – only subtle hints of a slight increase, suggesting that dark matter is not leaving any obvious trace in the charged particles detected from space.
Nobody knows exactly what dark matter is, but the leading theoretical model posits that it is made of up of particles called WIMPs (weakly interacting massive particles). When two WIMPS collide, the theory says, they annihilate, producing radiation and a cascade of particles, including electrons.
So researchers were excited last November, when a team studying data from two ATIC balloon flights over Antarctica reported finding many more electrons than expected at high energies around 600 gigaelectronvolts. Less exotic objects, such as pulsars and supernova remnants, also accelerate charged particles to high energies, so the ATIC data could potentially be explained by such garden-variety fare.
But the abundance and high energies of the 'extra' electrons detected, coupled with another unexpected cosmic ray result measured a few months earlier by a satellite called PAMELA, raised the tantalising possibility that dark matter – perhaps of an exotic type – might be responsible.
"Particle physicists have not had much to get excited about in the last 10 years – they were all ready for the Large Hadron Collider and then had a big setback" when it broke down, says Douglas Finkbeiner, a dark matter theorist at the Harvard-Smithsonian Center for Astrophysics. "Then PAMELA and ATIC came along with extra high-energy signals that could not be easily explained, and it was fun to think about."
Now, however, astrophysicists using the Fermi telescope say they don't see a dramatic spike in the number of high-energy electrons in space. "Our energy spectrum doesn't have prominent features," says Alexander Moiseev, a Fermi team leader at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
Pros and cons
What could explain the discrepancy? For one thing, the two experiments have different strengths and weaknesses.
ATIC flew in Earth's atmosphere, which can create extra "noise" in its signal, while Fermi is a space mission. ATIC's balloon flights also lasted for no more than three weeks, while Fermi is constantly taking data from orbit.
Indeed, the Fermi team analysed more than 4 million high-energy electrons detected with the telescope over the course of about six months to arrive at their result, collecting hundreds of times more data at these energies than any previous measurement. "We are practically free of statistical errors," Moiseev told New Scientist.
But ATIC has a thicker calorimeter, an instrument at the bottom of its detector that incoming space particles strike, generating showers of other particles. "The deeper or thicker that calorimeter is, the less of that shower energy sneaks out the bottom," says ATIC team leader John Wefel of Louisiana State University in Baton Rouge.
"They can contain 68% of the energy, and we contain 85% of the energy," Wefel told New Scientist. As a result, he says there is more uncertainty in Fermi's measurement of the energy of incoming particles, which could broaden out any dramatic spikes like the one seen by ATIC.
"The reason they're not seeing that peak structure is because they have much poorer energy resolution in their instrument," says Wefel. He adds that his team has analysed a third balloon flight since the original ATIC announcement in November and finds the same sharp peak as before.
Instrumental effect?
The Fermi team acknowledges that it has a thinner calorimeter but says its detector is better in other ways – it boasts an instrument that tracks the path of incoming particles, for example – something that ATIC does not have. It has also run detailed computer algorithms that show its energy resolution is sharp enough to be able to see a spike in energetic electrons. "We would see an ATIC-like bump with huge confidence if it were there," maintains Moiseev.
Gregory Tarle, a physicist at the University of Michigan who is not affiliated with either team, agrees. The bump seen by ATIC "was probably an instrumental effect they hadn't compensated for", he says.
Both experiments have to grapple with the same basic challenge, Tarle explains – distinguishing between electrons and the much more abundant protons that pass through their detectors from space. Since neither experiment uses a magnetic field that could tell the two kinds of charged particles apart, the teams must try to do this by analysing the characteristics of the particle showers in their detectors.
"It's hard to make these measurements – very hard," says Tarle. But he says Fermi's calorimeter is better suited for the analysis than ATIC's. It is made of atoms that have a higher number of protons, which do not readily interact with protons coming in from space. That causes "less contamination in the electron
So if the ATIC bump isn't real, what does that mean for dark matter?
Tarle says it means that high-energy electron detectors such as ATIC and Fermi do not show any evidence for dark matter. "There's nothing in their data that could indicate new physics," he says.
But other researchers say Fermi's data does show what may be a subtle sign of dark matter. If they look at the data in the most conservative way, Fermi team members do not see this potential signature – they say the electron energy spectrum they measure is smooth, without any wiggles that might indicate 'extra' electrons.
If they are not as conservative, however, Fermi team members say they see a slight bump in the number of electrons at higher energies – though nothing as dramatic as ATIC's.
That gentle bump, they say, might be due to a slight theoretical underestimation of how many high-energy cosmic rays are produced in objects such as pulsars – an idea Tarle favours.
"The most likely explanation of the excess electrons at high energy seen by Fermi is that the theoretical estimates are wrong," Tarle says. "There is no reason to believe that these theoretical predictions based on lower energy data are valid in the high-energy regime of Fermi."
'Hard to fit'
Alternatively, it might be due to one or more nearby sources that are pumping out energetic electrons. The sources are thought to be nearby because high-energy electrons lose energy as they travel through space, so for them to arrive at the energies that Fermi detects, they must have come from somewhere within about 3000 light years of Earth.
The nearby sources could be pulsars, but "dark matter is not ruled out" as a possible source, says Moiseev.
Finkbeiner agrees. Last year, he and colleagues came up with a new model of dark matter that could account for both the PAMELA and ATIC signals.
After the Fermi team released its results at a physics meeting earlier this week, Finkbeiner said his inbox was flooded with emails saying, "So, annihilating dark matter is dead, right?" he says. "Nothing could be further from the truth."
"It was always a little bit hard to fit the ATIC bump," he says, explaining that such a sharp spike hints that dark matter might be annihilating straight to electrons – a process that is theoretically forbidden.
'Less information'
His and other dark matter models instead argue that annihilating dark matter particles create intermediate particles – such as pions – before producing electrons.
"It's hard to make a sharp feature but easy to make a broad, smooth feature" like the one Fermi may be seeing, he says, adding that the same is true for electrons produced in astrophysical sources such as pulsars.
"In a way, it's a relief we don't have to make the ATIC bump, but if ATIC is real, it would really be telling us something," Finkbeiner told New Scientist. "We're not likely to learn as much about dark matter from [Fermi's electron spectrum] – basically, we have less information than we had before."
Tricky observation
If further observations with Fermi suggest there is not even a gentle rise in the number of high-energy electrons it detects, that will make any annihilating dark matter difficult to observe – but it will necessarily not rule it out, says Finkbeiner.
"Before the ATIC and PAMELA results, the expected annihilation signal for the leading dark matter candidate, the WIMP, was much smaller, so failure to find a signal with Fermi does not in any way rule out conventional WIMP annihilation," he says.
"Of course, there could be no signal at all: dark matter could just sit there and gravitate and do absolutely nothing else," he adds. "That's kind of the most boring scenario: we can never learn what kind of particle it is."
Tracing the source
The Fermi team hopes to shed light on the issue by continuing to collect electron data from all over the sky. It's difficult to trace the source of electrons that fall into its detector because the charged particles are diverted by magnetic fields in space. But if Fermi detects even a slight excess of electrons in one region of the sky, it might point to their source, says Moiseev.
Fermi is also hunting for possible signs of dark matter in the distribution of gamma-ray photons in the sky. Gamma rays are thought to be produced by annihilating dark matter and unlike electrons, are not affected by intervening magnetic fields (see Where will new Fermi telescope find dark matter?).
Future experiments might also provide a cross-check of both ATIC and Fermi. One, called the Alpha Magnetic Spectrometer, may fly to the International Space Station before the shuttles are retired in 2010. It uses a magnetic field to separate charged particles and has a calorimeter a little thicker than Fermi's.
Journal reference: Physical Review Letters (vol 102, p 181101)
Tuesday, May 5, 2009
NASA's Fermi Explores High-energy "Space Invaders"
From Nasa.gov
Since its launch last June, NASA's Fermi Gamma-ray Space Telescope has discovered a new class of pulsars, probed gamma-ray bursts and watched flaring jets in galaxies billions of light-years away. Today at the American Physical Society meeting in Denver, Colo., Fermi scientists revealed new details about high-energy particles implicated in a nearby cosmic mystery.
"Fermi's Large Area Telescope is a state-of-the-art gamma-ray detector, but it's also a terrific tool for investigating the high-energy electrons in cosmic rays," said Alexander Moiseev, who presented the findings. Moiseev is an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md.
Cosmic rays are hyperfast electrons, positrons, and atomic nuclei moving at nearly the speed of light. Astronomers believe that the highest-energy cosmic rays arise from exotic places within our galaxy, such as the wreckage of exploded stars.
Fermi's Large Area Telescope (LAT) is exquisitely sensitive to electrons and their antimatter counterparts, positrons. Looking at the energies of 4.5 million high-energy particles that struck the detector between Aug. 4, 2008, and Jan. 31, 2009, the LAT team found evidence that both supplements and refutes other recent findings.
Compared to the number of cosmic rays at lower energies, more particles striking the LAT had energies greater than 100 billion electron volts (100 GeV) than expected based on previous experiments and traditional models. (Visible light has energies between two and three electron volts.) The observation has implications similar to complementary measurements from a European satellite named PAMELA and from the ground-based High Energy Stereoscopic System (H.E.S.S.), an array of telescopes located in Namibia that sees flashes of light as cosmic rays strike the upper atmosphere.
Last fall, a balloon-borne experiment named ATIC captured evidence for a dramatic spike in the number of cosmic rays at energies around 500 GeV. "Fermi would have seen this sharp feature if it was really there, but it didn't." said Luca Latronico, a team member at the National Institute of Nuclear Physics (INFN) in Pisa, Italy. "With the LAT's superior resolution and more than 100 times the number of electrons collected by balloon-borne experiments, we are seeing these cosmic rays with unprecedented accuracy."
Unlike gamma rays, which travel from their sources in straight lines, cosmic rays wend their way around the galaxy. They can ricochet off of galactic gas atoms or become whipped up and redirected by magnetic fields. These events randomize the particle paths and make it difficult to tell where they originated. In fact, determining cosmic-ray sources is one of Fermi's key goals.
What's most exciting about the Fermi, PAMELA, and H.E.S.S. data is that they may imply the presence of a nearby object that's beaming cosmic rays our way. "If these particles were emitted far away, they’d have lost a lot of their energy by the time they reached us," explained Luca Baldini, another Fermi collaborator at INFN.
If a nearby source is sending electrons and positrons toward us, the likely culprit is a pulsar -- the crushed, fast-spinning leftover of an exploded star. A more exotic possibility is on the table, too. The particles could arise from the annihilation of hypothetical particles that make-up so-called dark matter. This mysterious substance neither produces nor impedes light and reveals itself only by its gravitational effects.
"Fermi's next step is to look for changes in the cosmic-ray electron flux in different parts of the sky," Latronico said. "If there is a nearby source, that search will help us unravel where to begin looking for it."
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership mission, developed in collaboration with the U.S. Department of Energy and important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.
Since its launch last June, NASA's Fermi Gamma-ray Space Telescope has discovered a new class of pulsars, probed gamma-ray bursts and watched flaring jets in galaxies billions of light-years away. Today at the American Physical Society meeting in Denver, Colo., Fermi scientists revealed new details about high-energy particles implicated in a nearby cosmic mystery.
"Fermi's Large Area Telescope is a state-of-the-art gamma-ray detector, but it's also a terrific tool for investigating the high-energy electrons in cosmic rays," said Alexander Moiseev, who presented the findings. Moiseev is an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md.
Cosmic rays are hyperfast electrons, positrons, and atomic nuclei moving at nearly the speed of light. Astronomers believe that the highest-energy cosmic rays arise from exotic places within our galaxy, such as the wreckage of exploded stars.
Fermi's Large Area Telescope (LAT) is exquisitely sensitive to electrons and their antimatter counterparts, positrons. Looking at the energies of 4.5 million high-energy particles that struck the detector between Aug. 4, 2008, and Jan. 31, 2009, the LAT team found evidence that both supplements and refutes other recent findings.
Compared to the number of cosmic rays at lower energies, more particles striking the LAT had energies greater than 100 billion electron volts (100 GeV) than expected based on previous experiments and traditional models. (Visible light has energies between two and three electron volts.) The observation has implications similar to complementary measurements from a European satellite named PAMELA and from the ground-based High Energy Stereoscopic System (H.E.S.S.), an array of telescopes located in Namibia that sees flashes of light as cosmic rays strike the upper atmosphere.
Last fall, a balloon-borne experiment named ATIC captured evidence for a dramatic spike in the number of cosmic rays at energies around 500 GeV. "Fermi would have seen this sharp feature if it was really there, but it didn't." said Luca Latronico, a team member at the National Institute of Nuclear Physics (INFN) in Pisa, Italy. "With the LAT's superior resolution and more than 100 times the number of electrons collected by balloon-borne experiments, we are seeing these cosmic rays with unprecedented accuracy."
Unlike gamma rays, which travel from their sources in straight lines, cosmic rays wend their way around the galaxy. They can ricochet off of galactic gas atoms or become whipped up and redirected by magnetic fields. These events randomize the particle paths and make it difficult to tell where they originated. In fact, determining cosmic-ray sources is one of Fermi's key goals.
What's most exciting about the Fermi, PAMELA, and H.E.S.S. data is that they may imply the presence of a nearby object that's beaming cosmic rays our way. "If these particles were emitted far away, they’d have lost a lot of their energy by the time they reached us," explained Luca Baldini, another Fermi collaborator at INFN.
If a nearby source is sending electrons and positrons toward us, the likely culprit is a pulsar -- the crushed, fast-spinning leftover of an exploded star. A more exotic possibility is on the table, too. The particles could arise from the annihilation of hypothetical particles that make-up so-called dark matter. This mysterious substance neither produces nor impedes light and reveals itself only by its gravitational effects.
"Fermi's next step is to look for changes in the cosmic-ray electron flux in different parts of the sky," Latronico said. "If there is a nearby source, that search will help us unravel where to begin looking for it."
NASA's Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership mission, developed in collaboration with the U.S. Department of Energy and important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.
Monday, May 4, 2009
Austrian breakthrough in quantum cryptography
from psyorg.com
Austrian physicists say a breakthrough in next-generation quantum cryptography could allow encrypted messages to be bounced off satellites, the British journal Nature reported Sunday.
A team from Austria's Institute for Quantum Optics and Quantum Information (IQOQI) managed to send entangled photons 144 kilometres (90 miles) between the Spanish islands of Las Palmas and the Balearics.
Because of the success of the test, the IQOQI team said it was now feasible to send this kind of unbreakable encrypted communication through space using satellites.
Quantum cryptography works by sending streams of light particles, or photons, making it entirely secure, as any eavesdropping would leave traces and immediately be detected.
In quantum cryptography, photons are used as the key for the encrypted communication -- just as mathematical formula are used in conventional cryptography.
Austrian physicists say a breakthrough in next-generation quantum cryptography could allow encrypted messages to be bounced off satellites, the British journal Nature reported Sunday.
A team from Austria's Institute for Quantum Optics and Quantum Information (IQOQI) managed to send entangled photons 144 kilometres (90 miles) between the Spanish islands of Las Palmas and the Balearics.
Because of the success of the test, the IQOQI team said it was now feasible to send this kind of unbreakable encrypted communication through space using satellites.
Quantum cryptography works by sending streams of light particles, or photons, making it entirely secure, as any eavesdropping would leave traces and immediately be detected.
In quantum cryptography, photons are used as the key for the encrypted communication -- just as mathematical formula are used in conventional cryptography.
Friday, May 1, 2009
Girl, 8, gets divorced in Saudi Arabia
By Richard Spencer in Dubai
The case has prompted the kingdom to re-evaluate its conservative attitudes to marriage.
The girl's marriage was arranged by her father and backed twice by a judge on the condition that it was not consummated until she reached puberty.
Her mother, who is separated from the father, objected to the arrangement and twice sought a divorce on her daughter's behalf. It was refused both times by the judge, Sheikh Habib Al-Habib, after the girl's husband refused to agree.
The judge did say that when the girl reached puberty she could herself seek a divorce.
The case was widely publicised and prompted heated debate in the country, which is currently giving more rights to women than have previously been granted. It was also condemned by human rights groups abroad.
King Abdullah, seen as a reformist, appointed the first ever woman deputy minister earlier this year.
One of his advisers, Mohsen al-Obaikan, an Islamic scholar, went public to demand that a legal age for marriage be set at 18. The justice ministry said it was considering reforming the law, which until now has given no minimum.
The justice minister said he wanted to end the "arbitrary" control of marriages by girl's fathers.
However, the country's highest religious authority, the Grand Mufti Sheikh Abdul Aziz al-Shaikh, said that marrying girls even under the age of 15 was not against Sharia - Islamic law which forms the basis of the Saudi legal system.
The Saudi Gazette reported that the marriage of the eight-year-old, who has never been named, was annulled in a private out-of-court settlement between the two families in the city of Onaiza.
Most such marriages are arranged by families in return for money. In this case, the father was said to need to pay off a personal debt to the husband, a friend.
The girl herself has been living with her mother, and was never told that she was married, or of the international controversy her case had provoked.
Earlier, Anne Veneman, director of Unicef, said: "Unicef joins many in voicing concern that child marriage contravenes accepted international standards of human rights."
The case has prompted the kingdom to re-evaluate its conservative attitudes to marriage.
The girl's marriage was arranged by her father and backed twice by a judge on the condition that it was not consummated until she reached puberty.
Her mother, who is separated from the father, objected to the arrangement and twice sought a divorce on her daughter's behalf. It was refused both times by the judge, Sheikh Habib Al-Habib, after the girl's husband refused to agree.
The judge did say that when the girl reached puberty she could herself seek a divorce.
The case was widely publicised and prompted heated debate in the country, which is currently giving more rights to women than have previously been granted. It was also condemned by human rights groups abroad.
King Abdullah, seen as a reformist, appointed the first ever woman deputy minister earlier this year.
One of his advisers, Mohsen al-Obaikan, an Islamic scholar, went public to demand that a legal age for marriage be set at 18. The justice ministry said it was considering reforming the law, which until now has given no minimum.
The justice minister said he wanted to end the "arbitrary" control of marriages by girl's fathers.
However, the country's highest religious authority, the Grand Mufti Sheikh Abdul Aziz al-Shaikh, said that marrying girls even under the age of 15 was not against Sharia - Islamic law which forms the basis of the Saudi legal system.
The Saudi Gazette reported that the marriage of the eight-year-old, who has never been named, was annulled in a private out-of-court settlement between the two families in the city of Onaiza.
Most such marriages are arranged by families in return for money. In this case, the father was said to need to pay off a personal debt to the husband, a friend.
The girl herself has been living with her mother, and was never told that she was married, or of the international controversy her case had provoked.
Earlier, Anne Veneman, director of Unicef, said: "Unicef joins many in voicing concern that child marriage contravenes accepted international standards of human rights."
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