TODAY.com?s Courtney Hazlett and comedian Chuck Nice run down the week?s celebrity news, including Justin Bieber?s wild week, Jessica Simpson?s Weight Watcher?s deal and Madonna's return to the concert stage.
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ScienceDaily (May 31, 2012) ? An international team of astronomers using data from the European Space Agency's (ESA) XMM-Newton satellite has identified a long-sought X-ray "echo" that promises a new way to probe supersized black holes in distant galaxies.
Most big galaxies host a big central black hole containing millions of times the sun's mass. When matter streams toward one of these supermassive black holes, the galaxy's center lights up, emitting billions of times more energy than the sun. For years, astronomers have been monitoring such "active galactic nuclei" (AGN) to better understand what happens on the brink of a monster black hole.
"Our analysis allows us to probe black holes through a different window. It confirms some long-held ideas about AGN and gives us a sense of what we can expect when a new generation of space-based X-ray telescopes eventually becomes available," said Abderahmen Zoghbi, a postdoctoral research associate at the University of Maryland at College Park (UMCP) and the study's lead author.
One of the most important tools for astronomers studying AGN is an X-ray feature known as the broad iron line, now regarded as the signature of a rotating black hole. Excited iron atoms produce characteristic X-rays with energies around 6,000 to 7,000 electron volts -- several thousand times the energy in visible light -- and this emission is known as the iron K line.
Matter falling toward a black hole collects into a rotating accretion disk, where it becomes compressed and heated before eventually spilling over the black hole's event horizon, the point beyond which nothing can escape and astronomers cannot observe. A mysterious and intense X-ray source near the black hole shines onto the disk's surface layers, causing iron atoms to radiate K-line emission. The inner part of the disk is orbiting the black hole so rapidly that the effects of Einstein's relativity come into play -- most notably, how time slows down close to the black hole. These relativistic effects skew or broaden the signal in a distinctive way.
Astronomers predicted that when the X-ray source near the black hole flared, the broad iron K line would brighten after a delay corresponding to how long the X-rays took to reach and illuminate the accretion disk. Astronomers call the process relativistic reverberation. With each flare from the X-ray source, a light echo sweeps across the disk and the iron line brightens accordingly.
Unfortunately, neither ESA's XMM-Newton satellite nor NASA's Chandra X-ray Observatory possess telescopes powerful enough to spot reverberations from individual flares.
he team reasoned that detecting the combined echoes from multiple flares might be possible if a sufficiently large amount of data from the right object could be analyzed. The object turned out to be the galaxy NGC 4151, which is located about 45 million light-years away in the constellation Canes Venatici. As one of the brightest AGN in X-rays, NGC 4151 has been observed extensively by XMM-Newton. Astronomers think that the galaxy's active nucleus is powered by a black hole weighing 50 million solar masses, which suggested the presence of a large accretion disk capable of producing especially long-lived and easily detectable echoes.
Since 2000, XMM-Newton has observed the galaxy with an accumulated exposure of about four days. By analyzing this data, the researchers uncovered numerous X-ray echoes, demonstrating for the first time the reality of relativistic reverberation. The findings appear in the May 8 issue of Monthly Notices of the Royal Astronomical Society.
The team found that echoes lagged behind the AGN flares by a little more than 30 minutes. Moving at the speed of light, the X-rays associated with the echo must have traveled an additional 400 million miles -- equivalent to about four times Earth's average distance from the sun -- than those that came to us directly from the flare.
"This tells us that the mysterious X-ray source in AGN hovers at some height above the accretion disk," said co-author Chris Reynolds, a professor of astronomy at UMCP and Zoghbi's adviser. Jets of accelerated particles often are associated with AGN, and this finding meshes with recent suggestions that the X-ray source may be located near the bases of these jets.
"The data show that the earliest echo comes from the most broadened iron line emission. This originates from closest to the black hole and fits well with expectations," said co-author Andy Fabian, an astrophysicist at the University of Cambridge in England.
Amazingly, the extreme environment at the heart of NGC 4151 is built on a scale comparable to our own solar system. If we replaced the sun with the black hole, the event horizon would extend less than halfway to Earth if the black hole spins rapidly; slower spin would result in a larger horizon. The X-ray source would hover above the black hole and its accretion disk at a distance similar to that between the sun and the middle of the asteroid belt.
"Teasing out the echo of X-ray light in NGC 4151 is a remarkable achievement. This work propels the science of AGN into a fundamental new area of mapping the neighborhoods of supermassive black holes," said Kimberly Weaver, an astrophysicist at NASA's Goddard Space Flight Center in Greenbelt, Md., who was not involved in the study. NASA Goddard hosts the XMM-Newton Guest Observer Facility, which supports U.S. astronomers who request observing time on the satellite.
The detection of X-ray echoes in AGN provides a new way of studying black holes and their accretion disks. Astronomers envision the next generation of X-ray telescopes with collecting areas large enough to detect the echo of a single AGN flare in many different objects, thereby providing astronomers with a new tool for testing relativity and probing the immediate surroundings of massive black holes.
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The researchers found that the more night shifts you work, the higher your risk, TIME reported May 29.
Exposure to artificial light at night ? the kind you?re likely to experience staying awake on the night shift ? suppresses the body?s melatonin levels and may cause other hormonal imbalances as well that could influence breast-cancer risk, the study authors speculate. Breast-cancer patients usually have lower levels of melatonin, research shows.
People who are predisposed to being early risers fare worse than women who are more comfortable being awake into the odd hours of the morning, the researchers find. ?Morning? types who pull night shifts have a four times higher risk of breast cancer than women who work during the day, the study says.
?It?s much worse to be a morning person and have night shift work when it comes to breast cancer,? study co-author Johnni Hansen, Ph.D., says.
The study appears online in the journal Occupational and Environmental Medicine.
(Photo ? tomislavmedak via Flickr)
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ScienceDaily (May 31, 2012) ? How can blue whales, the largest animals on the planet, survive by feeding on krill, shrimp-like creatures that are the size of a penny? According to UCLA life scientists, it's all a matter of dimensions.
In findings published May 30 in the journal Nature, the researchers demonstrate for the first time that the relationship between animals' body size and their feeding rate -- the overall amount of food they consume per unit of time -- is largely determined by the properties of the space in which they search for their food.
An animal searching for food in a three-dimensional space, like the ocean or sky, is likely to consume much more than a similarly sized animal searching in a flat, two-dimensional space, like a savannah or a sea bed, they found.
"Surprisingly, the spatial dimension of the search space turns out to be the most important property," said Van Savage, senior author of the research and a UCLA assistant professor of ecology and evolutionary biology and of biomathematics. "Yet up until now, work on food webs and predator-prey relationships has almost universally assumed that feeding rate increases with body size in a way that is independent of dimensionality."
Animals, of course, cannot simply go to the market when they are hungry. Instead, they must search for their food, which can also move in space. Cheetahs, for instance, scan the savannah for gazelle in two dimensions (left-to-right, forward-to-backward), while sharks search the ocean and some birds, such as flycatchers, scour the skies in 3-D (with an added up-and-down dimension).
"Would you rather search for food in two dimensions or three?" Savage asks. "That is, would you rather search for food just left-to-right and forward-to-backward on the floor of a room, or would you also want to search up-and-down, from floor to ceiling? When I quiz people, including scientists, most say they would rather search in two dimensions because it would be easier to find food. But we found that in nature the third dimension usually adds a huge number of extra resources. Ultimately, searching in this extra dimension provides many more chances to find food."
The UCLA researchers developed a new mathematical model that predicted that feeding rates increase more quickly with body size in three dimensions than in two. The model helps explain why huge whales can subsist on tiny krill in three dimensions -- but likely could not in two dimensions, if they had evolved to live on land.
To test their ideas and model predictions, the researchers compiled and analyzed the largest-ever database on relationships between feeding rates and body size. They were surprised to discover how well the data fit their predictions.
"I was amazed that the data and theoretical predictions match so well," said Samraat Pawar, lead author of the study and a UCLA postdoctoral scholar in Savage's group. "After spending so many months working on the theory and wondering if it really connected to reality and then spending so many more months finding and analyzing real data for feeding relationships, I knew it was very meaningful when they matched.
"When looking across species, an increase in consumer size leads to a much faster increase in feeding rate in three dimensions than in two dimensions. Moreover, for two consumers of the same body size, the one in three dimensions will typically have a much higher feeding rate than the one in two dimensions. Our results reminded me of Edwin Abbott's book 'Flatland,' in which denizens of a two-dimensional world are trapped in an ostensibly inferior existence due to their inability to perceive the third spatial dimension."
This is one of the first demonstrations, Pawar added, that uses both theory and data to show that dimensionality has important implications for ecology.
The ultimate goal of the research, the scientists say, is predicting how climate change will affect biodiversity levels and, thus for humans, the availability of goods and services, such as food and plants, fungi or bacteria used to make pharmaceuticals. The new findings suggest there may be crucial differences in how climate change will affect ecosystems that are more two dimensional, such as land and water surfaces, and those that are three dimensional, such as the open ocean or air.
The study also predicts that the stronger feeding interactions in three dimensions -- that is, the tendency for animals to consume more than they would in two dimensions -- will lead more often to boom-and-bust cycles in the abundance of species, analogous to large fluctuations seen in stocks or housing prices. These booms and busts make species more prone to extinction and therefore "could have profound consequences for understanding and preserving biodiversity in different habitats and for the planet as a whole," Savage said.
What made the UCLA study "unique and allowed for the discovery of new patterns was the researchers' focus on pairs of species -- just one 'consumer' species feeding on just one 'resource' species -- for both the modeling and data," said study co-author Anthony Dell, a UCLA researcher in Savage's group.
"Previous studies looked at many species together and at properties of whole ecological systems or whole food webs that describe all potential feeding relationships," Dell said. "All of the existing food-web models assume that dimensionality does not affect how feeding rates increase with body size. However, we found there is both a strong and systematic interdependence that should be straightforward to incorporate into models and data analysis. Our findings mean that a lot of the previous work may need to be revised."
Savage's research group also has a unique approach that utilizes perspectives from physics and applied mathematics to study biological problems.
"Having been trained in theoretical particle physics, I automatically consider dimensionality as part of any problem, but I was impressed by how large the effect is here," Savage said. "Dimensionality has long been considered important in physics, where people think about string theory and extra dimensions of space."
The scientists are currently looking at the effects of temperature -- another major driver of feeding rates -- and studying how to combine that with the results of the current study on feeding rates and dimensionality.
The research was federally funded by the National Science Foundation.
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The above story is reprinted from materials provided by University of California, Los Angeles. The original article was written by Stuart Wolpert.
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