Wednesday, 23 July 2014

"Google Street View" of the Cosmos Unveiled


A new home-grown instrument based on bundles of optical fibres is giving Australian astronomers the first 'Google street view' of the cosmos — incredibly detailed views of huge numbers of galaxies. Developed by researchers at the University of Sydney and the Australian Astronomical Observatory, the optical-fibre bundles can sample the light from up to 60 parts of a galaxy, for a dozen galaxies at a time. The technological leap is the 'hexabundle', sixty or more optical fibres close-packed and fused together, developed by the University of Sydney's astrophotonics group.

Using the new instrument astronomers from the Australian National University and the University of Sydney have already spotted 'galactic winds'—streams of charged particles travelling at up to 3,000 km a second—from the center of two galaxies.
"We've seen galactic winds in other galaxies, but we have no idea how common they really are, because we've never had the means to look for them systematically. Now we do," said the University of Sydney's Associate Professor Scott Croom, a Chief Investigator on the project.

By analysing the light's spectrum astronomers can learn how gas and stars move within each galaxy, where the young stars are forming and where the old stars live. This will allow them to better understand how galaxies change over time and what drives that change.

"It's a giant step," said Dr James Allen of the ARC Centre of Excellence for All-sky Astrophysics(CAASTRO) at the University of Sydney. "Before, we could study one galaxy at a time in detail, or lots of galaxies at once but in much less detail. Now we have both the numbers and the detail."

The Australian team is now a year or two ahead of its international competition in this field. In just 64 nights it has gathered data on 1000 galaxies, twice as many as the previous largest project, and over the next two years it will study another 2000.

Called SAMI (the Sydney-AAO Multi-Object Integral field spectrograph), the optical-fibre instrument was installed on the 4-m Anglo-Australian Telescope at Siding Spring Observatory in northwest NSW last year.

The researchers are also uncovering the formation history of galaxies by looking to see if they are rotating in a regular way or if the movement of their stars is random and disordered.

"There are hints that galaxies with random motions sit at the centres of groups of galaxies, where many smaller galaxies may have fallen into them," said Dr Lisa Fogarty, a CAASTRO researcher at the University of Sydney who led this work.

On Thursday 24 July the researchers will release the first set of data from the instrument to the worldwide astronomical community and Dr Allen will give a related presentation at the annual scientific meetingof the Astronomical Society of Australia.
Read More

Monday, 21 July 2014

Dwarf Galaxies "Challenge Our Understanding of How the Universe Works"


"Early in 2013 we announced our startling discovery that half of the dwarf galaxies surrounding the Andromeda Galaxy are orbiting it in an immense plane," said Geraint Lewis, of the University of Sydney's School of Physics. "This plane is more than a million light years in diameter, but is very thin, with a width of only 300 000 light years. Everywhere we looked we saw this strangely coherent coordinated motion of dwarf galaxies. From this we can extrapolate that these circular planes of dancing dwarfs are universal, seen in about 50 percent of galaxies," Lewis added. "This is a big problem that contradicts our standard cosmological models. It challenges our understanding of how the universe works including the nature of dark matter."

The researchers believe the answer may be hidden in some currently unknown physical process that governs how gas flows in the universe, although, as yet, there is no obvious mechanism that can guide dwarf galaxies into narrow planes.
Some experts, however, have made more radical suggestions, including bending and twisting the laws of gravity and motion. "Throwing out seemingly established laws of physics is unpalatable," said Professor Lewis, "but if our observations of nature are pointing us in this direction, we have to keep an open mind. That's what science is all about."

This discovery, that many small galaxies throughout the universe do not 'swarm' around larger ones like bees do but 'dance' in orderly disc-shaped orbits, is a challenge to our understanding of how the universe formed and evolved. The finding, by an international team of astronomers, including Lewis, is announced today in Nature.

The universe contains billions of galaxies. Some, such as the Milky Way, are immense, containing hundreds of billions of stars. Most galaxies, however, are dwarfs, much smaller and with only a few billion stars.

For decades astronomers have used computer models to predict how these dwarf galaxies should orbit large galaxies. They had always found that they should be scattered randomly.

"Our Andromeda discovery did not agree with expectations, and we felt compelled to explore if it was true of other galaxies throughout the universe," said Professor Lewis.

Using the Sloan Digital Sky Survey, a remarkable resource of colour images and 3-D maps covering more than a third of the sky, the researchers dissected the properties of thousands of nearby galaxies.

"We were surprised to find that a large proportion of pairs of satellite galaxies have oppositely directed velocities if they are situated on opposite sides of their giant galaxy hosts", said lead author Neil Ibata of the Lycée International in Strasbourg, France.
Read More

"Signs of Alien Life" --Viewing Earth from an Extraterrestrial Spacecraft

From afar, Earth-like worlds appear as tiny points of light, making it hard to imagine ever finding out much about them. The best we can do with telescope technology at the moment is to examine some atmospheric components of worlds that are larger than Jupiter. But that doesn’t mean we should discount the possibility of ever finding a planet similar in size to our own, researchers say. Telescopes are only getting more powerful.
“We’re trying to think about how to use observations of the Earth itself to understand the kinds of things we’ll be able to do in the future with possibly the next generation of telescopes,” said Robert Fosbury, an emeritus astronomer with the European Southern Observatory (ESO) who participated in the research.

Fosbury and leading researcher Fei Yan, an astronomer with ESO and the University of Chinese Academy of Sciences, examined the shadow of the Earth during a lunar eclipse. While there is no facility at ESO that is dedicated to astrobiology, Fosbury said the researchers are thinking closely about the implications for life beyond Earth.

Observations took place during a total lunar eclipse on Dec. 10, 2011. A lunar eclipse appears as the Earth moves between the Moon and the Sun, and is visible anywhere the sky is dark and clear with the Moon above the horizon.

A lunar eclipse is easier to observe than a total solar eclipse, which appears when the Moon passes between the Earth and the Sun. During a solar eclipse, the Moon’s shadow is so small that it creates a brief few minutes of totality and a small “track” of shadow visible from the Earth’s surface.

In this study, the researchers made observations with the High Resolution Spectrograph mounted on a 2.16-meter telescope at Xinglong Station, China, and focused the telescope near the Moon’s Tycho Crater because that is where the Moon has high reflectivity.

The researchers hoped to learn more about the Earth’s spectrum, which is shown in the Moon’s reflection. A spectrum is the band of colors that makes up visible light, and is most readily recognized in a rainbow. Certain elements preferentially emit certain wavelengths of light, and absorb others. By using a spectrograph to examine another planet, for example, you can see what atoms or molecules are present in its atmosphere or surface.

Watching the Earth’s light reflected by the Moon is similar to watching an exoplanet transit across the face of its parent star, the astronomers said. In both cases, finding the absorbing molecules in the atmosphere is a process of subtraction. In the case of an exoplanet, astronomers compare the molecular absorptions in the starlight during and after the transit. In the case of the Moon, astronomers compared the elements found in the Earth’s shadow, and when the Moon was clear of the shadow.

During the eclipse, the science team took spectra when the Moon was in the shadow (umbra) of the Earth. The Moon turns red during this time because most of the light you see is a refraction of sunlight through the Earth’s atmosphere (it’s all the sunsets and sunrises on the Earth seen at once). The scientists also compared the spectrum of the Moon when it was completely out of the shadow.

After removing some effects generated by the local atmosphere, the researchers examined the spectrum of colors to see what molecules were visible. A few surprises popped up. For example, they didn’t see as much water vapor in the signature as observers saw in a 2009 eclipse that encompassed much of the Northern Hemisphere. (That paper, “Earth’s transmission spectrum from lunar eclipse observations,” was published in Nature.)

Researchers in the newer study concluded that the absence of water vapor was because the “path” of the 2011 transit in the Earth’s atmosphere included the Antarctic, where much of the water is presumed to be frozen out of the atmosphere.

Another surprise was the abundance of nitrogen dioxide. Normally the nitrogen dioxide is regarded as a pollutant produced by human activities. The Antarctic, however, is quite a barren location — but it did have a volcano.

“We found that the track we observed is close to a volcano, and this volcano can potentially produce nitrogen dioxide,” Yan said. He added that other explanations could be possible. In this case, the volcano (Mount Erabus) may not be active enough to produce large amount of nitrogen dioxide. Further investigation found that the nitrogen dioxide was a bio-product of nitrous oxide (which is produced naturally by microbes) that then lingered in the atmosphere and reacted with ozone, creating nitrogen dioxide.

“This was during the spring, and the ice melted in the spring, and according to the vulcanologists this melt releases a lot of nitrous oxide,” Fosbury said.

If we were to look at Earth as an exoplanet, could the nitrogen dioxide be interpreted as a sign of pollution, of microbial life or of a volcano? Fosbury said it depends on context. If the planet had an abundance of volcanoes on its surface, you would assume it was likely, principally, from the volcanoes. If those weren’t easily visible, it would be harder to draw conclusions about life, but it would be possible. He pointed out that nitrogen dioxide is normally associated with pollution.

“It’s over Los Angeles and Beijing and all of those places because of how the catalysis of exhaust [from cars] works.”

When looking for an extraterrestrial civilization, pollution chemicals should be included on the list of “signs” of life, he added. Ozone might also be visible. Fosbury pointed out that at higher latitudes, at the edge of the umbra on the moon, you can see blue.

“It’s one of the indicators that there’s a lot of ozone,” he said. “Ozone actually is a very prominent and very important marker for Earth-like planets,” Fosbury said.

ESO, whose astronomical facilities are based in Chile, also has at least two major contributions to exoplanet research. The High Accuracy Radial velocity Planet Searcher (HARPS) at the ESO La Silla 3.6-meter telescope measures small variations in stellar velocities as planets orbit them. This instrument was used for the first ever detection of an exoplanet.

Also under construction is the European Extremely Large Telescope (E-ELT), a 39-meter beast that will not only do these velocity measurements, but also image some planets and possibly characterize their atmospheres. This research will come in handy when the E-ELT and NASA’s James Webb Space Telescope are working.

“This will be quite an investment over a long period of time,” Fosbury added. “As we learn more about the practicalities of doing these observations, we’ll be in a better position to not only perform the observations, but design the kinds of instruments that will be needed.”

The paper, “High resolution transmission spectrum of the Earth’s atmosphere: Seeing Earth as an exoplanet using a lunar eclipse,” is available on the pre-publishing site Arxiv and has been accepted in the International Journal of Astrobiology.
Read More

Tuesday, 15 July 2014

"Explosive Microbial Growth Caused Earth's Greatest Extinction Event" --The Great Dying (Today's Most Popular)

The end-Permian (or PT) extinction event occurred 252 million years ago. It is often called the Great Dying because around 90 percent of marine species disappeared in one fell swoop. Similar numbers died on land as well, producing a stark contrast between Permian rock layers beneath (or before) the extinction and the Triassic layers above. Extinctions are common throughout time, but for this one, the fossil record truly skipped a beat.
"The end-Permian is the greatest extinction event that we know of," said Daniel Rothman, a geophysicist at the Massachusetts Institute of Technology. "The changes in the fossil record were obvious even to 19th Century geologists."

Understanding the cause of this biological devastation requires understanding the geochemical clues that go along with it. Chief among these clues is a sudden swing in the balance of carbon isotopes stored in rocks from that same time period. If geologists can find what disrupted the carbon, they'll likely know what killed off so much of the Earth's life forms. Several theories have tried to explain the carbon perturbation as, for example, massive volcanism, or a drop in sea level, but none of these environmental causes have fully matched the data.

With this genetic innovation, these methane-producers, or methanogens, ran rampant across the ocean, overturning the carbon cycle. The resulting changes in ocean chemistry would have driven many species to extinction.

"This shows how unstable Earth's systems are," Rothman said. "A very small event in the microbial community can have an enormous impact on the environment." The basis of this new theory comes from a reassessment of the carbon data.

A plot of data on mass extinctions in Earth's history. The end-Permian extinction event is the large peak on the left at 250 million years ago. Credit: University of Chicago For decades, geologists have been aware that the ratio of carbon isotopes (the light verses heavy forms of the element) changed abruptly in geological samples around the time of the end-Permian event. Specifically, the carbon stored in rocks tilted towards the lighter isotope by about 1 percent over a matter of 100,000 years.

Rothman and his colleagues re-analyzed these isotope fluctuations, incorporating them into a model of dynamical exchange between different reservoirs of carbon material. The results showed that the level of carbon dioxide in the ocean rose faster than exponentially. The increase was slow at first, but picked up pace as time went on.

Rothman and his collaborators argue that no geological source can adequately explain the dramatic growth of carbon dioxide. One popular theory has been that high levels of carbon dioxide were released by massive volcanic eruptions in Siberia, which lasted for a million years and covered a million square miles with lava.

"It's hard to get the arithmetic right with just volcanoes," Rothman said.

He and his fellow authors believe an additional input is needed – one coming from biology. A burst in biological activity could explain the exponential-like growth in the ocean's carbon dioxide reserve.

Exponential-like growth is not uncommon in biology. Certain invasive species, for example, experience population explosions once they enter a new ecosystem. Similar types of expansion can occur when an evolutionary development gives a particular species a leg up on its competition.

The authors contend that some sort of biological innovation altered the distribution of carbon in the ocean. And they assume that the ocean was, in some sense, waiting for this innovation with a large reservoir of organic material (the detritus from dead organisms) in the ocean sediment.

"Other research has shown that during the end Permian, these organic products had accumulated to very high levels, probably due to a slowdown of normal degradation," said Greg Fournier, a co-author also from MIT.

This organic sediment was like "a big pile of food" for an enterprising organism to exploit.

Fournier had a clue as to what sort of organism this might be. From previous work he had done as a NASA Astrobiology Institute (NAI) postdoctoral fellow, he knew that a major innovation occurred around this time period in a type of methane-spewing archaea called Methanosarcina.

This methanogen is currently found all over the place, Fournier says, with species inhabiting marine and freshwater sediments, soils, sewage, and even inside the guts of animals such as cattle, where they produce a lot of the methane released into the world.

Part of Methanosarcina's success is due to the fact that these organisms can process acetate, a common organic residue, faster than some of their methanogen cousins. Basically, the Methanosarcina are able to get more energy out of the conversion of acetate to methane.

Fournier had earlier shown that Methanosarcina had acquired this ability from horizontal gene transfer. In some long-ago microbial tryst, an ancient methanogen (which produced methane as waste) swapped genes with an ancient cellulose-eating bacterium (which produced acetate as waste). This genetic "technology transfer" created an organism that could more efficiently metabolize acetate.

To obtain a more precise date for when this microbial innovation happened, Fournier and his colleagues performed a rigorous genetic analysis.

"We compared genomes from a variety of different methanogens and dated the evolution of this [new metabolic pathway] by using a calibrated 'clock' that counts the changes accumulated in genes over time," Fournier said.

MIT professor of geophysics Daniel Rothman stands next to part of the Xiakou formation in China. His right hand rests on the layer that marks the time of the end-Permian mass extinction event. Samples from this formation provided evidence for large amounts of nickel that were spewed from volcanic activity at this time, 252 million years ago. The results placed the gene-swapping event at 240 million years ago, plus or minus 40 million years.

"The molecular clock analysis simply confirms that, to the best of our ability to measure, the timing is consistent with [the end-Permian event]," Fournier said.

If indeed the genetic innovation occurred in the late Permian, then it's reasonable to assume that the Methanosarcina population began to multiply. Much of the methane produced by these organisms would have converted — through oxidation reactions or biological processing — into carbon dioxide, causing a rise in the carbon dioxide levels of the ocean.

The conversion of methane into carbon dioxide would have had a secondary effect as well: it would have driven down the amount of oxygen in the ocean water. Because Methanosarcina is anaerobic, the reduction in oxygen would have helped them thrive even more, creating a positive feedback loop. This could explain the faster than exponential growth in carbon dioxide concentrations that the authors observed.

As previous scientists have argued, the high levels of carbon dioxide would have led to a more acidic ocean, which would have been especially deadly for shell-bearing lifeforms. And like a house of cards, many other species followed suit.

One possible sticking point is that exponential-like growth often gets ahead of itself and becomes a victim of its own success. In biology, overgrown populations tend to run out of food or some other resource.

In the case of methanogens, this limiting resource might have been the element nickel, which these organisms need to produce metabolic enzymes. The levels of nickel in the ocean are not typically very high.

"If methanogens were to become active, they could be limited by nickel," Rothman said.

However, when the team checked nickel concentrations in late Permian geological samples, they found a spike that corresponded with the carbon isotope fluctuations. The source of this high nickel abundance was most likely the massive volcanic activity in Siberia, where the world's largest nickel deposits are located. That spike in nickel allowed methanogens to take off.

"It's a nice confirmation because it closes a circle, so to speak, by bringing the story back to volcanism," Rothman said.

"It is a novel idea that will need a lot of testing to see if it has 'legs'," said geologist David Bottjer of the University of Southern California, who was not involved with this work.

The arguments seem valid to him, but it will take some time for "the process of science to unwind as we see how this new idea stands up to earlier proposed mechanisms."

Rothman said they are currently studying whether the methanogens may have left some sort of biomarker, for example an organic compound, which could provide further support for the scenario. "[The authors] have done a really nice job linking the latest geo-chronologic age constraints on the duration of the extinction to the changes in the carbon cycle," said paleontologist Douglas Erwin of the Smithsonian Institution.

But Erwin thinks the emphasis on methanogens is misplaced.

"Their suggestion that the PT [extinction] was instigated by a 'specific microbial innovation' suggests a misunderstanding of causality," he said.

To his thinking, volcanism is the ultimate cause, since it triggered the methanogen growth by creating favorable conditions.

Rothman admits that's one way to look at it, but he doesn't think the volcanoes (and their release of nickel) were necessary for the explosive microbial growth. Instead, he calls the volcanism a "catalytic event" that helped propel the genetic innovation.

"There is a random component to biological evolution," said Fournier. "This gene transfer occurs by chance, but is only selected for and expands through a population when it conveys a specific advantage, which would be realized under those conditions [brought on by the volcanism]."

Either way, it's impressive how interdependent all these different elements appear to have been.

"The clear implication is that life and the environment have co-evolved," Rothman said.

The image at the top of the page by Jonathan Blair shows the 10-foot (0.3-meter) predator Dinogorgon, whose skull is shown floodplains in the heart of today's South Africa. In less than a million years Dinogorgon vanished in the greatest mass extinction ever, along with about nine of every ten plant and animal species on the planet.
Read More

Wednesday, 9 July 2014

“Origin of Life is Not the Same as the Origin of a Biosphere" --A New Look at the Once Watery Worlds of Venus and Mars

The oldest signs of life on Earth date to about 3.5 billion years ago. But when did our planet transition from having organisms to having a biosphere? “It’s hard to tell—it’s something that hasn’t been studied enough,” Grinspoon says. “But my guess is that once life has some kind of global influence, then you’re transitioning to a biosphere.”
Grinspoon’s work focuses on the evolution of climate and atmosphere on Earth-like planets. At a recent conference themed Habitable Worlds Across Time and Space, held at the Space Telescope Science Institute in Baltimore, MD, he discussed the implications of this viewpoint for Earth’s nearest neighbors: Venus and Mars.

The three rocky planets formed around the same time, some 4.5 billion years ago. Just like Earth, Venus and Mars may once have been watery worlds. Today they seem dry and barren, but several lines of evidence suggest they both had oceans in their early days.

“Everything we know about them points to an early environment that was hospitable for life,” Grinspoon says in an interview with Astrobiology Magazine. But somehow only Earth held onto its water, and eventually burst out with the self-sustaining fire of life. “Maybe what’s rare is not the formation of watery planets, but the persistence of habitable environments over cosmological timescales,” he says.

By the end of his talk, titled “Venus and Mars as Failed Biospheres,” Grinspoon raises an intriguing question. Is a biosphere necessary for the long-term survival of life?

To Grinspoon, the shift on Earth had likely occurred by 2.3 billion years ago, or around the time photosynthetic microbes began churning out oxygen into Earth’s oceans and atmosphere, affecting life’s survival everywhere on the planet.

However, life’s influence went way beyond its power to shape the Earth’s atmosphere. According to recent studies, life has shaped everything from Earth’s interior to the diversity of minerals on its surface. As Grinspoon puts it, “Life has got Earth in its clutches in this deep, and not always obvious way.”

“Can a planet, in a sense, become alive?” Grinspoon asks.

It’s not the first time he puts the concept forward. In his 2003 book Lonely Planets, Grinspoon introduced the “Living World” hypothesis, a slight variant the well-known Gaia hypothesis.

In the 1970s, the chemist James Lovelock and the biologist Lynn Margulis developed the idea that our Earth may be like a living organism, a self-regulating entity that employs feedback loops to keep conditions just right for life. They christened the potentially living planet “Gaia,” from the Greek for Mother Earth.

The idea has since been hotly debated, mostly pegged as more philosophical than scientific. Still, many researchers agree that the concept has helped Earth system science move forward, allowing us to realize that many of Earth’s cycles—the water, nitrogen, and carbon cycles; plate tectonics; and the climate—are deeply interconnected, and is modulating and being modulated by life on Earth.

“Gaia may just be a nice metaphor,” Grinpsoon says, “but I wonder if it may be fruitful to think of life as something that happens not just on a planet, but as something that happens to a planet.”

“You cannot easily separate the living and the non-living parts of Earth,” he adds. “Life has made Earth the way it is to a large extent. That’s the general meaning of the Gaia hypothesis, and the Living Worlds hypothesis is simply extending the idea to other planets.”

“The idea of an origin of life separated from the birth of a living world has interesting implications for life elsewhere,” Grinspoon writes in Lonely Planets: “If self-regulating Gaia is responsible for Earth’s life longevity, then we need to find other places where this kind of global organism has evolved, not merely places where the origin of life might once have occurred.”

In other words, our search for life should then target places with active geological and meteorological cycles, the potential tell-tales of a vibrant biosphere.

We’ve now found nearly 2,000 planets orbiting distant stars, and counting. While these worlds may be too far for us to find any direct evidence for life in the near future, researchers are becoming increasingly proficient at making out the composition of their atmosphere. That ability could perhaps one day allow us to distinguish between “failed biospheres” and potentially living worlds.

In the meantime, a Living World perspective may yield useful insights as we target our search for life closer to home, in our own solar system. Jupiter’s icy moon, Europa, seems to have a young and active surface, while Saturn’s moon, Titan, is meteorologically well-alive with methane raining down and filling rivers and lakes.

Even our closest neighbor, Venus, long viewed as a hellish world with its extreme heat, crushing pressure, and clouds of sulfuric acid, could potentially host some kind of life, if vigorous cycles are any indicators of a healthy biosphere, as Grinspoon argued in his 1997 book, Venus Revealed.

For Mars it would be a different story, with its stale atmosphere of carbon dioxide and its rusty, quiet surface. “From a living worlds perspective, the new wave of interest in life on Mars is highly questionable,” Grinspoon wrote in Lonely Planets.

But even if Mars seems dead now, it may not be the end of it for the Red Planet. By 2030, the mission “Mars One” will aim to establish the first human settlement. In the end, the “fire” which started on Earth 3.5 billion years ago could soon leap and catch on elsewhere.
Read More

Tuesday, 8 July 2014

Something is Amiss with Light in the Universe --"Photons May Be Coming from Some Exotic Unknown Source"


The vast reaches of empty space between galaxies are bridged by tendrils of hydrogen and helium, which can be used as a precise "light meter." In a recent study published in The Astrophysical Journal Letters, a team of scientists finds that the light from known populations of galaxies and quasars is not nearly enough to explain observations of intergalactic hydrogen. The difference is a stunning 400 percent.

"The most exciting possibility is that the missing photons are coming from some exotic new source, not galaxies or quasars at all," said Neal Katz a co-author from the University of Massachusetts at Amherst. For example, the mysterious dark matter, which holds galaxies together but has never been seen directly, could itself decay and ultimately be responsible for this extra light.
"You know it's a crisis when you start seriously talking about decaying dark matter!" Katz remarked.

"The great thing about a 400% discrepancy is that you know something is really wrong," commented co-author David Weinberg of The Ohio State University. "We still don't know for sure what it is, but at least one thing we thought we knew about the present day universe isn't true."

"It's as if you're in a big, brightly-lit room, but you look around and see only a few 40-watt lightbulbs," noted Carnegie's Juna Kollmeier, lead author of the study. "Where is all that light coming from? It's missing from our census."

Strangely, this mismatch only appears in the nearby, relatively well-studied cosmos. When telescopes focus on galaxies billions of light years away (and therefore are viewing the universe billions of years in its past), everything seems to add up. The fact that this accounting works in the early universe but falls apart locally has scientists puzzled.

The light in question consists of highly energetic ultraviolet photons that are able to convert electrically neutral hydrogen atoms into electrically charged ions. The two known sources for such ionizing photons are quasars—powered by hot gas falling onto supermassive black holes over a million times the mass of the sun—and the hottest young stars.

Observations indicate that the ionizing photons from young stars are almost always absorbed by gas in their host galaxy, so they never escape to affect intergalactic hydrogen. But the number of known quasars is far lower than needed to produce the required light.

"Either our accounting of the light from galaxies and quasars is very far off, or there's some other major source of ionizing photons that we've never recognized," Kollmeier said. "We are calling this missing light the photon underproduction crisis. But it's the astronomers who are in crisis—somehow or other, the universe is getting along just fine."

The mismatch emerged from comparing supercomputer simulations of intergalactic gas to the most recent analysis of observations from Hubble Space Telescope's Cosmic Origins Spectrograph. "The simulations fit the data beautifully in the early universe, and they fit the local data beautifully if we're allowed to assume that this extra light is really there," explained Ben Oppenheimer a co-author from the University of Colorado. "It's possible the simulations do not reflect reality, which by itself would be a surprise, because intergalactic hydrogen is the component of the Universe that we think we understand the best."

The image at the top of the page shows a type Ia supernovae that are brighter than whole galaxies and visible billions of light-years away. The Supernova Cosmology Project devised ways of finding Type Ia supernovae “on demand,” then measured the expansion of the universe with a precision that led to the discovery of dark energy.
Read More

Closing in On Gravitational Waves --"Will Be a Clear Message About How the Universe is Put Together"


Many large heavenly bodies and events in the universe, such as the birth and death of stars, generate energy in different wavelengths of light, which existing telescopes can find, says Nergis Mavalvala, the Curtis and Kathleen Marble Professor of Astrophysics at MIT. But compact astrophysical objects — such as neutron stars and light-eating black holes, which are believed to produce energy in the form of gravitational wave radiation — remain concealed from human view. These waves, unlike light, she says, “flow through everything, because matter is basically transparent to them. They come to us unobstructed right from the source.” For Mavalvala, gravitational waves are “a clean messenger bearing information about how the universe is put together.”

These ripples in the fabric of space-time — the signature of violent cosmic events — are “extremely aloof,” Mavalvala says. In fact, gravitational waves have been dodging elaborate efforts by scientists to track them down since Einstein predicted their existence a century ago.
But last March brought a possible breakthrough: Astronomers at the Harvard-Smithsonian Center for Astrophysics discovered what appears to be the first direct evidence of gravitational waves. For Mavalvala, the Curtis and Kathleen Marble Professor of Astrophysics, the news could not be more thrilling. It willherald a new era of astronomical discovery “It will be exciting beyond measure, and the greatest excitement will be finding things we can’t yet imagine," she says.

Sincethe early 1990s, MIT has been designing and building the Laser Interferometer Gravitational-Wave Observatory (LIGO). For helping design this complex and finely tuned scientific tool for detecting gravitational waves, Mavalvala won a MacArthur Fellowship in 2010.

LIGO’s instrument for detecting the extremely faint signature of gravitational waves is “an exquisitely sensitive interferometer,” Mavalvala says. It measures the time it takes for light beamed from a laser to strike a mirror four kilometers away and reflect back. Theoretically, a gravitational wave arriving on earth and passing between laser and mirror will slow down the light as it bounces, thus changing the distance between the two infinitesimally. LIGO is built to identify a change in distance of 10 to 18 meters — 1,000 times smaller than a proton.

Members of an international team, Mavalvala, and her lab colleagues have been refining the laser interferometer, specifically the optical sensing and control system. In the past several years, two observatories have started up — one in Washington state and the other in Louisiana — but have not yet yielded results. LIGO researchers are now sharpening their focus by a factor of 10. “This allows us to be sensitive either to weaker gravitational waves, or to the same sources, such as a pair of neutron stars colliding, but farther out,” Mavalvala says.

Engaged with LIGO’s second-generation detectors, Mavalvala is contending with a critical problem involving the instrument’s measuring precision. But she has some clever tricks to sidestep these constraints. One deploys “squeezed light sources” — laser beams whose quantum properties are manipulated to reduce noise fluctuations — that may improve the sensitivity of the LIGO detectors and render more accurate measurements.

“The big picture mission drives you. When you work in the lab, [it's like] you bang your head against the wall for weeks at a time, working on a state-of-the-art circuit, for example,” Mavalvala says. “Yet this is what enables scientific discovery, when the smaller to bigger pieces of experiments succeed, when the whole thing does what it is supposed to, and then you hope nature gives you the event you’ve been waiting for.”

The image at the top of the page shows the Sagittarius Dwarf Galaxy, named for the constellation in which it is seen from the earth, in the process of colliding and merging with our own Milky Way. Up to now, most astronomical research has focused on the effects of the collision on the Sagittarius dwarf itself, because the vast gravity and tidal forces exerted by the large Milky Way is ripping the smaller galaxy apart into long streamers of stars wrapping around our own Galaxy.

Read More

Monday, 7 July 2014

Tiny Dwarf Galaxies Lit and Shaped the Early Universe

Shortly after the Big Bang, the universe was ionised: ordinary matter consisted of hydrogen with its positively charged protons stripped of their negatively charged electrons. Eventually, the universe cooled enough for electrons and protons to combine and form neutral hydrogen. This cool gas will eventually form the first stars in the universe but for millions of years, there are no stars. Astronomers therefore aren't able to see how the cosmos evolved during these 'dark ages' using conventional telescopes. The light returned when newly forming stars and galaxies re-ionised the universe during the 'epoch of re-ionisation'.
Astronomers agree that the universe became fully re-ionised roughly one billion years after the Big Bang. About 200 million years after the birth of the cosmos, ultraviolet (UV) radiation from stars began to split neutral hydrogen into electrons and protons. It took another 800 million years to complete the process everywhere. This epoch of re-ionisation marked the last major change to gas in the universe, and it remains ionised today, over 12 billion years later.

However, astronomers aren't in agreement on which type of galaxies played the most important role in this process. Most have focused on large galaxies. The new study by researchers at the Georgia Institute of Technology and the San Diego Supercomputer Center indicates scientists should also focus on the smallest ones.

A view of the entire simulation volume showing the large scale structure of the gas, which is distributed in filaments and clumps. The red regions are heated by UV light coming from the galaxies, highlighted in white.


The researchers used computer simulations to demonstrate the faintest and smallest galaxies in the early universe were essential. These tiny galaxies – despite being 1000 times smaller in mass and 30 times smaller in size than our own Milky Way galaxy – contributed nearly 30 percent of the UV light during this process.

A zoomed-in view of the most massive dwarf galaxy in the simulation, seen when the universe was only 700 million years old. This galaxy only has 3 million solar masses of stars, compared to 60 billion solar masses in our Milky Way. The yellow points represent the older and cooler stars in the galaxy, and the blue points show the young and massive stars forming just before this snapshot of the simulation. The haze around the stars show the gas distribution in the galaxy with blue and red representing hot and cold temperatures, respectively.


"It turns out these dwarf galaxies did form stars, usually in one burst, around 500 million years after the Big Bang," said Prof. John Wise, of the Georgia Institute of Technology, who led the study. "The galaxies were small, but so plentiful that they contributed a significant fraction of UV light in the re-ionisation process."

The team's simulations modelled the flow of UV stellar light through the gas within galaxies as they formed. They found that the fraction of ionizing photons escaping into intergalactic space was 50 percent in small galaxies (more than 10 million solar masses). It was only 5 percent in larger galaxies (300 million solar masses). This elevated fraction, combined with their high abundance, is exactly the reason why the faintest galaxies play an integral role during re-ionisation.

"It's very hard for UV light to escape galaxies because of the dense gas that fills them," said Wise. "In small galaxies, there's less gas between stars, making it easier for UV light to escape because it isn't absorbed as quickly. Plus, supernova explosions can open up channels more easily in these tiny galaxies in which UV light can escape."

The team's simulation results provide a gradual timeline that tracks the progress of re-ionisation over hundreds of millions of years. About 300 million years after the Big Bang, the universe was 20 per cent ionised. It was 50 per cent at 550 million years. The simulated universe was fully ionised at 860 million years after its creation.

"That such small galaxies could contribute so much to re-ionisation is a real surprise," said Prof. Michael Norman, of the University of California San Diego and one of the co-authors of the paper. "Once again, the supercomputer is teaching us something new and unexpected; something that will need to be factored into future studies of re-ionisation."

A rendering above of a simulation that follows the formation of the first galaxies in the universe. The field of view is adjusted to account for the expansion of the universe, where the scale bar represents 32,600 light-years (10,000 parsecs). The video shows hot and ionised gas in blue, and cold and neutral gas in red. The intensity of each pixel is set by the gas density, and the stars are not shown in this visualisation. The video runs from 200 million to 800 million years after the Big Bang.

In the image at the top of the page, 75,000 light years from Earth, a galaxy known as Segue 1 has some unusual properties: It is the faintest galaxy ever detected. It is very small, containing only about 1,000 stars. And it has a rare chemical composition, with vanishingly small amounts of metallic elements present.

A team of scientists recently analyzed the galaxy's chemical composition and come away with new insights into the evolution of galaxies in the early stages of our universe — or, in this case, into a striking lack of evolution in Segue 1. Commonly, stars form from gas clouds and then burn up as supernova explosions after about a billion years, spewing more of the elements that are the basis for a new generation of star formation.

Not Segue 1: In contrast to all other galaxies, as the new analysis shows, it appears that Segue 1's process of star formation halted at what would normally be an early stage of a galaxy's development.

"It's chemically quite primitive," says Anna Frebel, an assistant professor of physics at MIT, and the lead author of a new paper detailing the new findings about Segue 1. "This indicates the galaxy never made that many stars in the first place. It is really wimpy. This galaxy tried to become a big galaxy, but it failed."

But precisely because it has stayed in the same state, Segue 1 offers valuable information about the conditions of the universe in its early phases after the Big Bang.

"It tells us how galaxies get started," Frebel says. "It's really adding another dimension to stellar archaeology, where we look back in time to study the era of the first star and first galaxy formation."

The analysis uses new data taken by the Magellan telescopes in Chile, as well as data from the Keck Observatory in Hawaii, pertaining to six red giant stars in Segue 1, the brightest ones in that galaxy. The astronomers are able to determine which elements are present in the stars because each element has a unique signature that becomes detectable in the telescope data.

In particular, Segue 1 has stars that are distinctively poor in metal content. All of the elements in Segue 1 that are heavier than helium appear to have derived either from just one supernova explosion, or perhaps a few such explosions, which occurred relatively soon after the galaxy's formation. Then Segue 1 effectively shut down, in evolutionary terms, because it lost its gas due to the explosions, and stopped making new stars.

"It just didn't have enough gas, and couldn't collect enough gas to grow bigger and make stars, and as a consequence of that, make more of the heavy elements," Frebel says. Indeed, a run-of-the-mill galaxy will often contain 1 million stars; Segue 1 contains only about 1,000.

The astronomers also found telling evidence in the lack of so-called "neutron-capture elements" — those found in the bottom half of the periodic table, which are created in intermediate-mass stars. But in Segue 1, Frebel notes, "The neutron-capture elements in this galaxy are the lowest levels ever found." This, again, indicates a lack of repeated star formation.

"It is very different than these other regular dwarf-type galaxies that had full chemical evolution," Frebel says. "Those are just mini-galaxies, whereas [Segue 1 is] truncated. It doesn't show much evolution and just sits there. We would like to find more"

Dwarf galaxies, astronomical modeling has found, appear to form building blocks for larger galaxies such as the Milky Way. The chemical analysis of Segue 1 sheds new light on the nature of those building blocks, as Frebel notes.

The research team expects to learn more about these faint galaxies when the next generation of telescopes is operational. For example, NASA's James Webb Space Telescope, scheduled to launch in 2018, will be able to see them. The team report their findings in a paper published today in the journal Monthly Notices of the Royal Astronomical Society.
Read More

Saturday, 5 July 2014

Solved! Puzzling Signals Thought Originating from Habitable-Zone Planets


Mysteries about controversial signals coming from a dwarf star considered to be a prime target in the search for extraterrestrial life now have been solved in research led by scientists at Penn State University. Some of the signals, it appears, which were suspected to be coming from two planets orbiting the star at a distance where liquid water could potentially exist, actually are coming from events inside the star itself, not from so-called "Goldilocks planets" where conditions are just right for supporting life.

"This result is exciting because it explains, for the first time, all the previous and somewhat conflicting observations of the intriguing dwarf star Gliese 581, a faint star with less mass than our Sun that is just 20 light years from Earth," said lead author Paul Robertson, a postdoctoral fellow at Penn State who is affiliated with Penn State's Center for Exoplanets and Habitable Worlds. As a result of this research, the planets now confirmed to be orbiting this dwarf star total exactly three.
"We also have proven that some of the other controversial signals are not coming from two additional proposed Goldilocks planets in the star's habitable zone, but instead are coming from activity within the star itself," said Suvrath Mahadevan, an assistant professor of astronomy and astrophysics at Penn State and a coauthor of the research paper. None of the three remaining planets, whose existence the research confirms, are solidly inside this star system's habitable zone, where liquid water could exist on a rocky planet like Earth.

Astronomers search for exoplanets by measuring shifts in the pattern of a star's spectrum -- the different wavelengths of radiation that it emits as light. These "Doppler shifts" can result from subtle changes in the star's velocity caused by the gravitational tugs of orbiting planets. But Doppler shifts of a star's "absorption lines" also can result from magnetic events like sunspots originating within the star itself -- giving false clues of a planet that does not actually exist. "In the search for low-mass planets," Mahadevan said, "accounting for the subtle signature of a magnetics events in the star is as important as obtaining the highest possible Doppler precision."

The research team made its discovery by analyzing Doppler shifts in existing spectroscopic observations of the star Gliese 581 obtained with the ESO HARPS and Keck HIRES spectrographs. The Doppler shifts that the scientists focused on were the ones most sensitive to magnetic activity. Using careful analyses and techniques, they boosted the signals of the three innermost planets around the star, but "the signals attributed to the existence of the two controversial planets disappeared, becoming indistinguishable from measurement noise," Mahadevan said. "The disappearance of these two signals after correcting for the star's activity indicates that these signals in the original data must have been produced by the activity and rotation of the star itself, not by the presence of these two suspected planets.

"Our improved detection of the real planets in this system gives us confidence that we are now beginning to sufficiently eliminate Doppler signals from stellar activity to discover new, habitable exoplanets, even when they are hidden beneath stellar noise, said Robertson. "While it is unfortunate to find that two such promising planets do not exist, we feel that the results of this study will ultimately lead to more Earth-like planets."

Older stars such as Gliese 581, an "M dwarf" star in the constellation Libra about one-third the mass of our Sun, have until now been considered highly attractive targets in the search for extraterrestrial life because they are generally less active and so are better targets for Doppler observations. "The new result from our research highlights a source of astrophysical noise even with old M dwarfs because the harmonics of the star's rotation can be in the same range as that of its habitable zone, raising the risk of false detections of nonexistent planets," Mahadevan said. "Higher-precision analysis for discovering Earth-like planets using spectrographs will be increasingly more necessary as next-generation spectrographs with the higher Doppler precision needed for detecting important subtle signatures come on line this decade -- like the Habitable Zone Planet Finder (HPF) that our team now is developing at Penn State."

In addition to Mahadevan and Robertson, other coauthors of the research include Penn State Graduate Student Arpita Roy and McDonald Observatory Research Scientist Michael Endl at the University of Texas. Penn State coauthors have affiliations with the Center for Exoplanets and Habitable Worlds and with the Astrobiology Research Consortium, both at Penn State.

The Daily Galaxy via The research received support from the National Science Foundation, the NASA Astrobiology Institute, the Penn State Center for Exoplanets and Habitable Worlds, the Penn State Eberly College of Science, and the Pennsylvania Space Grant Consortium.

This image above shows the location of the three planets remaining in 2014. Research published in 2014, led by Penn State astronomers, shows that two of the signals previously attributed to planets in the habitable zone are actually created by activity within the star itself. The outer (green) planet shown in the 2010 image also is believed not to exist, based on work by other researchers since 2010. Blue indicates candidate planets in the habitable zone where conditions might be able to support life, orange indicates detections in the too-hot region that is too close to the star.

This animation shows planets believed to orbit the red dwarf star Gliese 581. These detections, made with the Doppler technique, were published in scientific papers from 2004 to 2014 and put some of the claimed planets in or near the star's habitable zone, where it might be possible for life as we know it to exist.

Blue indicates detections of candidate planets in the just-right region inside or near the habitable zone, where liquid water could exist. Orange indicates detections in the too-hot region that is too close to the star. Green indicates detections in the too-cold region farther away from the star and outside the habitable zone.

New research led by astronomers at Penn State University and published in the journal Science has disproved the existence of two of these controversial "Goldilocks planets," showing, instead, that the signals resulted from magnetic activity of the star, not from an orbiting planet. The three planets shown in the 2014 frames of this animation are the only ones that the study found to be actual planets, while the other two detections result from the star's own activity signals.

The size of each planet in this figure corresponds to its minimum mass. Some simplifications have been made for illustrative purposes. The refereed literature <> provides a complete history of the scientific publications relevant to this star and its planets.

The background image is a composite photo of our Sun taken by Alan Friedman. The left side of the Sun is seen through a filter that allows the camera to see wavelengths of light only in the deep-blue range, while the right side is seen through a filter that blocks all wavelengths except those in the red range. While the blue region is traditionally used to detect a star's activity, this study used the red region of the light spectrum.
Read More

Thursday, 3 July 2014

NASA's Cassini Probe Unlocks New Mysteries on Saturn's Titan


"Titan continues to prove itself as an endlessly fascinating world, and with our long-lived Cassini spacecraft, we're unlocking new mysteries as fast as we solve old ones," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory. JPL scientists analyzing data from NASA's Cassini mission have firm evidence the ocean inside Saturn's largest moon, Titan, might be as salty as Earth's Dead Sea.

The new results come from a study of gravity and topography data collected during Cassini's repeated flybys of Titan during the past 10 years. Using the Cassini data, researchers presented a model structure for Titan, resulting in an improved understanding of the structure of the moon's outer ice shell. The findings are published in this week's edition of the journal Icarus.
Additional findings support previous indications the moon's icy shell is rigid and in the process of freezing solid. Researchers found that a relatively high density was required for Titan's ocean in order to explain the gravity data. This indicates the ocean is probably an extremely salty brine of water mixed with dissolved salts likely composed of sulfur, sodium and potassium. The density indicated for this brine would give the ocean a salt content roughly equal to the saltiest bodies of water on Earth.

"This is an extremely salty ocean by Earth standards," said the paper's lead author, Giuseppe Mitri of the University of Nantes in France. "Knowing this may change the way we view this ocean as a possible abode for present-day life, but conditions might have been very different there in the past."

Cassini data also indicate the thickness of Titan's ice crust varies slightly from place to place. The researchers said this can best be explained if the moon's outer shell is stiff, as would be the case if the ocean were slowly crystalizing and turning to ice. Otherwise, the moon's shape would tend to even itself out over time, like warm candle wax. This freezing process would have important implications for the habitability of Titan's ocean, as it would limit the ability of materials to exchange between the surface and the ocean.

A further consequence of a rigid ice shell, according to the study, is any outgassing of methane into Titan's atmosphere must happen at scattered "hot spots" -- like the hot spot on Earth that gave rise to the Hawaiian Island chain. Titan's methane does not appear to result from convection or plate tectonics recycling its ice shell.

How methane gets into the moon's atmosphere has long been of great interest to researchers, as molecules of this gas are broken apart by sunlight on short geological timescales. Titan's present atmosphere contains about five percent methane. This means some process, thought to be geological in nature, must be replenishing the gas. The study indicates that whatever process is responsible, the restoration of Titan's methane is localized and intermittent.

"Our work suggests looking for signs of methane outgassing will be difficult with Cassini, and may require a future mission that can find localized methane sources," said Jonathan Lunine, a scientist on the Cassini mission at Cornell University, Ithaca, New York, and one of the paper's co-authors. "As on Mars, this is a challenging task."
Read More

Wednesday, 2 July 2014

"The Higgs Paradox" --Quantum-Level Discovery Fails to Solve Large-Scale Cosmic Mysteries


The Higgs boson is a cornerstone of the Standard Model, a theory developed in the early 1970s to explain the five percent of the Universe composed of visible matter and energy, all carried by fundamental particles. Now, two years after making history by unearthing the Higgs boson, the particle that confers mass, physicists are broadening their probe into its identity, hoping this will also solve other great cosmic mysteries. The better they become acquainted with the Higgs at the infinitely small quantum level, the further the experts seem from explaining certain cosmic-scale questions, like dark matter.

"The observed characteristics of the Higgs boson, such as its mass, interaction strengths and life-time, provide very powerful constraints on our understanding of the more fundamental theory," Valya Khoze, director of the Institute for Particle Physics Phenomenology (IPPP) at Durham University, told AFP (PARIS).
From next year, scientists will smash sub-atomic particles at ever higher-speeds in the upgraded Large Hadron Collider (LHC) near Geneva, which announced the Higgs discovery on July 4, 2012. Not only will they hope for new particles to emerge, but also for the Higgs to show signs of, well, weirdness.So far, the Higgs has conformed well to the traits predicted in the Standard Model of particle physics, the mainstream theory of how our Universe is constructed.

The model has weaknesses in that it doesn't explain dark matter or dark energy, which jointly make up 95 percent of the Universe. Nor is it compatible with the theory of gravity. Scientists have proposed alternative theories to explain the inconsistencies -- like supersymmetry which postulates the existence of a "sibling" for every particle in the Universe and may explain dark matter and dark energy.

No proof of such symmetric particles has been found at the LHC, currently in sleep mode for an 18-month overhaul to super-boost its power levels.

Supersymmetry, additionally, predicts the existence of at least five types of Higgs boson, and physicists will thus be watching the LHC Higgs closely for signs of behaviour inconsistent with the Standard Model. "It would give us a very good hint that there is physics there beyond the Standard Model and that there's new, additional physics coming soon," said Dave Charlton, who heads the ATLAS experiment at the LHC, a facility of the European Organisation for Nuclear Research (CERN) which celebrated its 60th anniversary on Tuesday. "It could help to explain many of the other problems we have in physics at the moment," he added.

For starters, they don't understand how it [the Higgs Boson] can have such a small mass. Nor is the evidence consistent for the role it played in the development of the early Universe after the Big Bang -- issues that may be resolved by so-called New Physics the experts hope will follow soon.

When the LHC fires up again next year, scientists will be on the lookout for new particles, including other types of Higgs, and possible "invisible decays" of the boson to indicate the presence of dark matter.

"All of the particles of the Standard Model have now been discovered," said Charlton."If we see new particles, it's something new... if we see new particles, it will point to something whether it is supersymmetry or some other new theory.

It will tell us that the Standard Model is broken, that there is something else."

Charlton said we may never know if the Higgs found at the LHC was exactly the Standard Model version or something that just resembles it.

Themis Bowcock, particle physics head at the University of Liverpool, said confirmation of several Standard Model predictions over the past two years have placed a new focus on what is not yet known. "It allows us to step back and view the boundaries of our knowledge with a keener eye," he told AFP. "We realise we have mastered our closest and most obvious challenges, but like a 15th century navigator we are motivated to venture beyond our mapped lands to discover the missing 95 percent -- the New World."
Read More

About Me

Designed ByBlogger Templates