An international team of scientists has identified a common phenomenon in galaxies that could explain why huge numbers of them turn into cosmic graveyards. Galaxies begin their existence as lively and colorful spiral galaxies, full of gas and dust, and actively forming bright new stars. However, as galaxies evolve, they quench their star formation and turn into featureless deserts, devoid of fresh new stars, and generally remain as such for the rest of their evolution. But the mechanism that produces this dramatic transformation and keeps galaxies turned off, is one of the biggest unsolved mysteries in galaxy evolution.

Now, thanks to the new large SDSS-IV MaNGA survey of galaxies, a collaborative effort led by the University of Tokyo and involving the University of Oxford has discovered a surprisingly common new phenomenon in galaxies, dubbed "red geysers", that could explain how the process works. Researchers interpret the red geysers as galaxies hosting low-energy supermassive black holes which drive intense interstellar winds. These winds suppress star formation by heating up the ambient gas found in galaxies and preventing it to cool and condense into stars.

Lead author Dr Edmond Cheung, from the University of Tokyo's Kavli Institute for the Physics and Mathematics of the Universe, said: 'Stars form from the gas, but in many galaxies stars were found not to form despite an abundance of gas. It was like having deserts in densely clouded regions. We knew quiescent galaxies needed some way to suppress star formation, and now we think the red geysers phenomenon may represent how typical quiescent galaxies maintain their quiescence.'

'Stars form from the gas, a bit like the drops of rain condense from the water vapour. And in both cases one needs the gas to cool down, for condensation to occur. But we could not understand what was preventing this cooling from happening in many galaxies,' said Co-author Dr Michele Cappellari, from the Department of Physics at Oxford University. 'But when we modeled the motion of the gas in the red geysers, we found that the gas was being pushed away from the galaxy center, and escaping the galaxy gravitational pull.'

'The discovery was made possible by the amazing power of the ongoing MaNGA galaxy survey' said Dr Kevin Bundy, from the University of Tokyo, the overall leader of the collaboration. 'The survey allows us to observe galaxies in three dimensions, by mapping not only how they appear on the sky, but also how their stars and gas move inside them.'

Using a near-dormant distant galaxy named Akira as a prototypical example, the researchers describe how the wind's driving mechanism is likely to originate in Akira's galactic nucleus. The energy input from this nucleus, powered by a supermassive black hole, is capable of producing the wind, which itself contains enough mechanical energy to heat ambient, cooler gas in the galaxy and thus suppress star formation.

The researchers identified an episodic quality to these jets of wind, leading them to the name red geysers (with 'red' colour due to the lack of blue young stars). This phenomenon, discussed in the paper with reference to Akira, appears surprisingly common and could be generally applicable to all quiescent galaxies.

The study made use of optical imaging spectroscopy from the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory (SDSS-IV MaNGA) program.

Does the image at the top of the page show one galaxy or two ? This question came to light in 1950 when astronomer Art Hoag chanced upon this unusual extragalactic object. On the outside is a ring dominated by bright blue stars, while near the center lies a ball of much redder stars that are likely much older. Between the two is a gap that appears almost completely dark. How Hoag's Object formed remains unknown, although similar objects have now been identified and collectively labeled as a form of ring galaxy. Genesis hypotheses include a galaxy collision billions of years ago and the gravitational effect of a central bar that has since vanished. The above photo taken by the Hubble Space Telescope in July 2001 revealed unprecedented details of Hoag's Object.

The Daily Galaxy via University of Oxford

Image credit: http://asterisk.apod.com/viewtopic.php?t=31821

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The European Space Agency's orbiting X-ray observatory, XMM-Newton, has proved the existence of a "gravitational vortex" around a black hole. The discovery, aided by NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) mission, solves a mystery that has eluded astronomers for more than 30 years, and will allow them to map the behavior of matter very close to black holes. It could also open the door to future investigations of Albert Einstein's general relativity.

Matter falling into a black hole heats up as it plunges to its doom. Before it passes into the black hole and is lost from view forever, it can reach millions of degrees. At that temperature it shines X-rays into space.

In the 1980s, pioneering astronomers using early X-ray telescopes discovered that the X-rays coming from stellar-mass black holes in our galaxy flicker. The changes follow a set pattern. When the flickering begins, the dimming and re-brightening can take 10 seconds to complete. As the days, weeks and then months progress, the period shortens until the oscillation takes place 10 times every second. Then, the flickering suddenly stops altogether. The phenomenon was dubbed the Quasi Periodic Oscillation (QPO).

"It was immediately recognized to be something fascinating because it is coming from something very close to a black hole," said Adam Ingram, University of Amsterdam, the Netherlands, who began working to understand QPOs for his doctoral thesis in 2009.

During the 1990s, astronomers had begun to suspect that the QPOs were associated with a gravitational effect predicted by Einstein's general relativity: that a spinning object will create a kind of gravitational vortex.

"It is a bit like twisting a spoon in honey. Imagine that the honey is space and anything embedded in the honey will be "dragged" around by the twisting spoon," explained Ingram. "In reality, this means that anything orbiting a spinning object will have its motion affected." In the case of an inclined orbit, it will "precess."

This means that the whole orbit will change orientation around the central object. The time for the orbit to return to its initial condition is known as a precession cycle.

In 2004, NASA launched Gravity Probe B to measure this so-called Lense-Thirring effect around Earth. After painstaking analysis, scientists confirmed that the spacecraft would turn through a complete precession cycle once every 33 million years.

Around a black hole, however, the effect would be much more noticeable because of the stronger gravitational field. The precession cycle would take just a matter of seconds or less to complete. This is so close to the periods of the QPOs that astronomers began to suspect a link.

Ingram began working on the problem by looking at what happened in the flat disc of matter surrounding a black hole. Known as an accretion disc, it is the place where material gradually spirals inwards towards the black hole. Scientists had already suggested that, close to the black hole, the flat accretion disc puffs up into a hot plasma, in which electrons are stripped from their host atoms. Termed the hot inner flow, it shrinks in size over weeks and months as it is eaten by the black hole. Together with colleagues, Ingram published a paper in 2009 suggesting that the QPO is driven by the Lense-Thirring precession of this hot flow. This is because the smaller the inner flow becomes, the closer to the black hole it would approach and so the faster its Lense-Thirring precession cycle would be. The question was: how to prove it?

"We have spent a lot of time trying to find smoking gun evidence for this behavior," said Ingram.

The answer is that the inner flow is releasing high-energy radiation that strikes the matter in the surrounding accretion disc, making the iron atoms in the disc shine like a fluorescent light tube. The iron releases X-rays of a single wavelength—referred to as "a spectral line."

Because the accretion disc is rotating, the iron line has its wavelength distorted by the Doppler effect. Line emission from the approaching side of the disc is squashed—blue shifted—and line emission from the receding disc material is stretched—red shifted. If the inner flow really is precessing, it will sometimes shine on the approaching disc material and sometimes on the receding material, making the line wobble back and forth over the course of a precession cycle.

Seeing this wobbling is where XMM-Newton came in. Ingram and colleagues from Amsterdam, Cambridge, Southampton and Tokyo applied for a long-duration observation that would allow them to watch the QPO repeatedly. They chose black hole H 1743-322, which was exhibiting a four-second QPO at the time. They watched it for 260,000 seconds with XMM-Newton. They also observed it for 70,000 seconds with NASA's NuSTAR X-ray observatory.

"The high-energy capability of NuSTAR was very important," Ingram said. "NuSTAR confirmed the wobbling of the iron line, and additionally saw a feature in the spectrum called a 'reflection hump' that added evidence for precession."

After a rigorous analysis process of adding all the observational data together, they saw that the iron line was wobbling in accordance with the predictions of general relativity. "We are directly measuring the motion of matter in a strong gravitational field near to a black hole," says Ingram.

This is the first time that the Lense-Thirring effect has been measured in a strong gravitational field. The technique will allow astronomers to map matter in the inner regions of accretion discs around black holes. It also hints at a powerful new tool with which to test general relativity.

Einstein's theory is largely untested in such strong gravitational fields. So if astronomers can understand the physics of the matter that is flowing into the black hole, they can use it to test the predictions of general relativity as never before - but only if the movement of the matter in the accretion disc can be completely understood.

"If you can get to the bottom of the astrophysics, then you can really test the general relativity," says Ingram. A deviation from the predictions of general relativity would be welcomed by a lot of astronomers and physicists. It would be a concrete signal that a deeper theory of gravity exists.

Larger X-ray telescopes in the future could help in the search because they are more powerful and could more efficiently collect X-rays. This would allow astronomers to investigate the QPO phenomenon in more detail. But for now, astronomers can be content with having seen Einstein's gravity at play around a black hole.

"This is a major breakthrough since the study combines information about the timing and energy of X-ray photons to settle the 30-year debate around the origin of QPOs. The photon-collecting capability of XMM-Newton was instrumental in this work," said Norbert Schartel, ESA Project Scientist for XMM-Newton.

The results reported in this article are published in "A quasi-periodic modulation of the iron line centroid energy in the black hole binary H 1743-322", by Adam Ingram and colleagues, to appear in Monthly Notices of the Royal Astronomical Society, 461 (2): 1967-1980

The Daily Galaxy via Monthly Notices of the Royal Astronomical

Image credit: Tomoharu Oka (Keio University)

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A new study of the early universe reveals how it could have been formed from an older collapsing universe, rather than being brand new. The universe is currently expanding and it is a common theory that this is the result of the ‘Big Bang' the universe bursting into existence from a point of infinitely dense and hot material.

"Our model's ability to give a possible solution to the problem of the Big Bang opens the way to new explanations for the formation of the universe," said Steffen Gielen, a theorectical physicist with the Imperial College of London.

However, physicists have long debated this idea as it means the universe began in a state of complete breakdown of physics as we know it. Instead, some have suggested that the universe has alternated between periods of expansion and contraction, and the current expansion is just one phase of this.

This so-called ‘Big Bounce' idea has been around since 1922, but has been held back by an inability to explain how the universe transitions from a contracting to an expanding state, and vice versa, without leading to an infinite point.

Now, in a new study published today in Physical Review Letters, Dr Steffen Gielen from Imperial College London and Dr Neil Turok, Director of the Perimeter Institute for Theoretical Physics in Canada, have shown how the Big Bounce might be possible.

Cosmological observations suggest that during its very early life, the universe may have looked the same at all scales meaning that the physical laws that that worked for the whole structure of the universe also worked at the scale of the very small, smaller than individual atoms. This phenomenon is known as conformal symmetry.

In today's universe, this is not the case particles smaller than atoms behave very differently to larger matter and the symmetry is broken. Subatomic particle behaviour is governed by what is called quantum mechanics, which produces different rules of physics for the very small.

For example, without quantum mechanics, atoms would not exist. The electrons, as they whizz around the nucleus, would lose energy and collapse into the centre, destroying the atom. However, quantum mechanics prevents this from happening.

In the early universe, as everything was incredibly small, it may have been governed solely by the principles of quantum mechanics, rather than the large-scale physics we also see today.

In the new study, the researchers suggest that the effects of quantum mechanics could prevent the universe from collapsing and destroying itself at end of a period of contraction, known as the Big Crunch. Instead, the universe would transition from a contracting state to an expanding one without collapsing completely.

Dr Gielen said: “Quantum mechanics saves us when things break down. It saves electrons from falling in and destroying atoms, so maybe it could also save the early universe from such violent beginnings and endings as the Big Bang and Big Crunch.”

Using the idea that the universe had conformal symmetry at its beginning, and that this was governed by the rules of quantum mechanics, Dr Gielen and Dr Turok built a mathematical model of how the universe might evolve.

The model contains a few simple ingredients that are most likely to have formed the early universe, such as the fact that it was filled with radiation, with almost no normal matter. With these, the model predicts that the effect of quantum mechanics would allow the universe to spring from a previous universe that was contracting, rather than from a single point of broken physics.

Dr Turok said: “The big surprise in our work is that we could describe the earliest moments of the hot Big Bang quantum mechanically, under very reasonable and minimal assumptions about the matter present in the universe. Under these assumptions, the Big Bang was a ‘bounce', in which contraction reversed to expansion.”

The researchers are now investigating how this simple model can be extended to explain the origin of perturbations to the simple structure of the universe, such as galaxies. “Our model's ability to give a possible solution to the problem of the Big Bang opens the way to new explanations for the formation of the universe,” said Dr Gielen.

'Perfect Quantum Cosmologial Bounce' by S Gielen and N Turok is published in Physical Review Letters.

The Daily Galaxy via Imperial College London

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Astronomers discovered a "Water World" planetary system this past April orbiting the star Kepler-62. This five-planet system has two worlds in the habitable zone — the distance from their star at which they receive enough light and warmth that liquid water could theoretically exist on their surfaces. Modeling by researchers at the Harvard-Smithsonian Center for Astrophysics (CfA) suggests that both planets are water worlds, their surfaces completely covered by a global ocean with no land in sight.

“These planets are unlike anything in our solar system. They have endless oceans,” said lead author Lisa Kaltenegger of the Max Planck Institute for Astronomy and the CfA. “There may be life there, but could it be technology-based like ours? Life on these worlds would be under water with no easy access to metals, to electricity, or fire for metallurgy. Nonetheless, these worlds will still be beautiful, blue planets circling an orange star — and maybe life's inventiveness to get to a technology stage will surprise us.”

Kepler-62 is a type K star slightly smaller and cooler than our sun. The two water worlds, designated Kepler-62e and -62f, orbit the star every 122 and 267 days, respectively. They were found by NASA's Kepler spacecraft, which detects planets that transit, or cross the face of, their host star. Measuring a transit tells astronomers the size of the planet relative to its star. The star system is illustrated below (CfA).

Kepler-62e is 60 percent larger than Earth, while Kepler-62f is about 40 percent larger, making both of them “super-Earths.” They are too small for their masses to be measured, but astronomers expect them to be composed of rock and water, without a significant gaseous envelope.

As the warmer of the two worlds, Kepler-62e would have a bit more clouds than Earth, according to computer models. More distant Kepler-62f would need the greenhouse effect from plenty of carbon dioxide to warm it enough to host an ocean. Otherwise, it might become an ice-covered snowball.

“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly,” said Harvard astronomer and co-author Dimitar Sasselov.

“The good news is — the two would exhibit distinctly different colors and make our search for signatures of life easier on such planets in the near future,” he added.

The discovery raises the intriguing possibility that some star in our galaxy might be circled by two Earth-like worlds — planets with oceans and continents, where technologically advanced life could develop.

“Imagine looking through a telescope to see another world with life just a few million miles from your own. Or, having the capability to travel between them on a regular basis. I can't think of a more powerful motivation to become a space-faring society,” said Sasselov.

Kaltenegger and Sasselov's research has been accepted for publication in The Astrophysical Journal.

The Daily Galaxy via CfA

Image credit: With thanks to higherdensity.wordpress.com

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If the origin of life is common on other worlds, the universe should be a cosmic zoo full of complex multicellular organisms. Dirk Schulze-Makuch, a Washington State University astrobiologist, uses the evolution of Earth life as a model to predict what humans might find living on distant planets and moons.

"If the origin of life can occur rather easily, a percentage of organisms on other worlds will reach higher levels of animal- or plant-like complexity," Schulze-Makuch said. "On the other hand, if the origin of life is a rare event, then chances are we live in a rather empty universe."

There are physical and chemical limits to how life can evolve, and scientists have determined that many of those requirements have been met on Earth. Therefore, the route Earthly lifeforms took from simple, single-celled organisms to successively more complex entities can give hints of how life might play out elsewhere in the cosmos.

In their study, Schulze-Makuch and Bains first identified the key evolutionary innovations that drove the development of Earth life from microbes to space-faring humans. These include the transition from single cell life to multicellular life, the rise of photosynthesis, the evolution of macroscopic life and the rise of intelligent life.

Then they analyzed whether or not these important evolutionary occurrences happened many times in different organisms or were due to random, isolated events.

They found that most of the critical innovations were "invented" several times. For example, photosynthesis originated independently at four different points in life's history, and multicellularity arose several times in different classes of organisms.

"Given that we have multiple examples of these key evolutionary adaptions occurring along the path from the simplest organism to humans, we must accept that they are not extremely improbable, but that it 'only' takes a long time and the proper conditions for them to arise," Schulze-Makuch said. "Therefore, in any world where life has arisen and sufficient energy flux exists, we are confident that we will find complex, animal-like life."

The one caveat is that the research doesn't address the likelihood of the origin of life occurring elsewhere or of there being aliens with human like intelligence. Earth is the only planet where life is known to exist, and humans are the only known species to have developed technology. So it is impossible to say whether this should be a common occurrence on other worlds, a very rare event or something in between, Schulze-Makuch said.

The work has major implications for the search for life on other worlds. Schulze-Makuch and Bains write that not only should scientists expect to find microbial biosignatures on a planet with life, but also signatures resulting from large and complex, multicellular organisms such as vegetation's red edge, which is the wavelength of light suggesting the existence of plant life.

"In particular, our research is relevant to the selection of tools scientists use in searching for life on planets in other solar systems," Schulze-Makuch said. "On future missions, researchers at NASA, the SETI (search for extraterrestrial intelligence ) Institute and other organizations should consider using instruments that are capable of finding signatures of a global and diverse biosphere on other worlds."

The Daily Galaxy via Washington State University

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Astronomers have believed since the 1960s that a galaxy dubbed UGC 1382 was a relatively boring, small elliptical galaxy. Ellipticals are the most common type of galaxy and lack the spiral structure of disks like the Milky Way we call home. Now, using a series of multi-wavelength surveys, astronomers have discovered that it is really a colossal Giant Low Surface Brightness disk galaxy that rivals the champion of this elusive class--a galaxy known as Malin 1. Malin 1 is some 7 times the diameter of the Milky Way.

Seibert explains: "Although there have been numerous surveys of the now-defunct elliptical since it was first cataloged in the 1960s, the only indication that it may be an unusual system was in 2009 when another survey indicated that there may be a hint of a rotating hydrogen disk, but it was not followed up. UGC 1382 came to our attention while we were looking at star formation in early-type galaxies using NASA's Galaxy Evolution Explorer (GALEX). We saw that in the ultraviolet part of the spectrum spiral arms were visible--something you do not expect to see around elliptical galaxies. Naturally, that finding sent us off on a very different path!"

Further investigation revealed that the hydrogen disk was real and has an enormous width. For comparison, our own Milky Way Galaxy has a width of 30 kiloparsecs (kpc), but UGC1382 is 220 kpc wide-about 7 times as large as the Milky Way. Despite the huge difference in size, the two systems weigh roughly the same. That is, they have very similar amounts of stars and gas.

Lea Hagen the lead author--a graduate student at the Pennsylvania State University and a former Carnegie summer student remarked, "It's unusual and surprising that we would have such a well-studied galaxy and miss its most unique property: a huge set of spiral arms. The fact that the spiral arms and hydrogen gas extend so far compared to most other galaxies makes this an exciting object for understanding the most extreme examples of galaxy evolution."

"A particularly attractive feature of the newly reclassified UGC 1382 is that it is much closer to us than Malin 1, about a quarter of the distance, in fact," remarked Seibert. "That proximity is what allowed us to conduct the multi-wavelength investigation and it will allow us to start to unravel how these extreme systems form and evolve. We know that such objects need to have a low-density environment without other large galaxies nearby that would disturb it, but they also need a supply of small but gas-rich 'dwarf' galaxies to accrete and build the really large diffuse extended disk. Unlike typical galaxy formation, however, the outer blue spiral disk appears to be older than the inner red disk. That is a big clue about how you get oddball giants like this."

Thus far, there have been about a dozen Giant Low Surface Brightness galaxies found, but none more extreme in size than Malin 1, which now has a rival in UGC 1382. The proximity of UGC 1382 will be a boon to revealing other features of such elusive giants in addition to understanding other seemingly normal early galaxies. The increased sensitivity of future telescopes and instruments may yield yet more discoveries of other misclassified galaxies.

The Daily Galaxy via Carnegie Institute for Science

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