Supercomputer Comes Up With A Profile Of Dark Matter

In the search for the mysterious dark matter, physicists have used elaborate computer calculations to come up with an outline of the particles of this unknown form of matter. To do this, the scientists extended the successful Standard Model of particle physics which allowed them, among other things, to predict the mass of so-called axions, promising candidates for dark matter. The German-Hungarian team of researchers led by Professor Zoltán Fodor of the University of Wuppertal, Eötvös University in Budapest and Forschungszentrum Jülich carried out its calculations on Jülich’s supercomputer JUQUEEN (BlueGene/Q) and presents its results in the journal Nature.

dark-matter

“Dark matter is an invisible form of matter which until now has only revealed itself through its gravitational effects. What it consists of remains a complete mystery,” explains co-author Dr Andreas Ringwald, who is based at DESY and who proposed the current research. Evidence for the existence of this form of matter comes, among other things, from the astrophysical observation of galaxies, which rotate far too rapidly to be held together only by the gravitational pull of the visible matter. High-precision measurements using the European satellite “Planck” show that almost 85 percent of the entire mass of the universe consists of dark matter. All the stars, planets, nebulae and other objects in space that are made of conventional matter account for no more than 15 percent of the mass of the universe.

“The adjective ‘dark’ does not simply mean that it does not emit visible light,” says Ringwald. “It does not appear to give off any other wavelengths either — its interaction with photons must be very weak indeed.” For decades, physicists have been searching for particles of this new type of matter. What is clear is that these particles must lie beyond the Standard Model of particle physics, and while that model is extremely successful, it currently only describes the conventional 15 percent of all matter in the cosmos. From theoretically possible extensions to the Standard Model physicists not only expect a deeper understanding of the universe, but also concrete clues in what energy range it is particularly worthwhile looking for dark-matter candidates.

The unknown form of matter can either consist of comparatively few, but very heavy particles, or of a large number of light ones. The direct searches for heavy dark-matter candidates using large detectors in underground laboratories and the indirect search for them using large particle accelerators are still going on, but have not turned up any dark matter particles so far. A range of physical considerations make extremely light particles, dubbed axions, very promising candidates. Using clever experimental setups, it might even be possible to detect direct evidence of them. “However, to find this kind of evidence it would be extremely helpful to know what kind of mass we are looking for,” emphasises theoretical physicist Ringwald. “Otherwise the search could take decades, because one would have to scan far too large a range.”

The existence of axions is predicted by an extension to quantum chromodynamics (QCD), the quantum theory that governs the strong interaction, responsible for the nuclear force. The strong interaction is one of the four fundamental forces of nature alongside gravitation, electromagnetism and the weak nuclear force, which is responsible for radioactivity. “Theoretical considerations indicate that there are so-called topological quantum fluctuations in quantum chromodynamics, which ought to result in an observable violation of time reversal symmetry,” explains Ringwald. This means that certain processes should differ depending on whether they are running forwards or backwards. However, no experiment has so far managed to demonstrate this effect.

The extension to quantum chromodynamics (QCD) restores the invariance of time reversals, but at the same time it predicts the existence of a very weakly interacting particle, the axion, whose properties, in particular its mass, depend on the strength of the topological quantum fluctuations. However, it takes modern supercomputers like Jülich’s JUQUEEN to calculate the latter in the temperature range that is relevant in predicting the relative contribution of axions to the matter making up the universe. “On top of this, we had to develop new methods of analysis in order to achieve the required temperature range,” notes Fodor who led the research.

The results show, among other things, that if axions do make up the bulk of dark matter, they should have a mass of 50 to 1500 micro-electronvolts, expressed in the customary units of particle physics, and thus be up to ten billion times lighter than electrons. This would require every cubic centimetre of the universe to contain on average ten million such ultra-lightweight particles. Dark matter is not spread out evenly in the universe, however, but forms clumps and branches of a weblike network. Because of this, our local region of the Milky Way should contain about one trillion axions per cubic centimetre.

Thanks to the Jülich supercomputer, the calculations now provide physicists with a concrete range in which their search for axions is likely to be most promising. “The results we are presenting will probably lead to a race to discover these particles,” says Fodor. Their discovery would not only solve the problem of dark matter in the universe, but at the same time answer the question why the strong interaction is so surprisingly symmetrical with respect to time reversal. The scientists expect that it will be possible within the next few years to either confirm or rule out the existence of axions experimentally.

The Institute for Nuclear Research of the Hungarian Academy of Sciences in Debrecen, the Lendület Lattice Gauge Theory Research Group at the Eötvös University, the University of Zaragoza in Spain, and the Max Planck Institute for Physics in Munich were also involved in the research.

New Model Explains The Moon’s Weird Orbit

The moon, Earth’s closest neighbor, is among the strangest planetary bodies in the solar system. Its orbit lies unusually far away from Earth, with a surprisingly large orbital tilt. Planetary scientists have struggled to piece together a scenario that accounts for these and other related characteristics of the Earth-moon system.

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A new research paper, based on numerical models of the moon’s explosive formation and the evolution of the Earth-moon system, comes closer to tying up all the loose ends than any other previous explanation. The work, published in the October 31, 2016 Advance Online edition of the journal Nature, suggests that the impact that formed the moon also caused calamitous changes to Earth’s rotation and the tilt of its spin axis.

The research suggests that the impact sent Earth spinning much faster, and at a much steeper tilt, than it does today. In the several billion years since that impact, complex interactions between Earth, the moon and sun have smoothed out many of these changes, resulting in the Earth-moon system that we see today. In this scenario, the remaining anomalies in the moon’s orbit are relics of the Earth-moon system’s explosive past.

“Evidence suggests a giant impact blasted off a huge amount of material that formed the moon,” said Douglas Hamilton, professor of astronomy at the University of Maryland and a co-author of the Nature paper. “This material would have formed a ring of debris first, then the ring would have aggregated to form the moon. But this scenario does not quite work if Earth’s spin axis was tilted at the 23.5 degree angle we see today.”

Collisional physics calls for this ring of debris — and thus the moon’s orbit immediately after formation — to lie in Earth’s equatorial plane. As tidal interactions between Earth and the moon drove the moon further away from Earth, the moon should have shifted from Earth’s equatorial plane to the “ecliptic” plane, which corresponds to Earth’s orbit around the sun.

But today, instead of being in line with the ecliptic plane, the moon’s orbit is tilted five degrees away from it.

“This large tilt is very unusual. Until now, there hasn’t been a good explanation,” Hamilton said. ” But we can understand it if Earth had a more dramatic early history than we previously suspected.”

Hamilton, with lead author Matija Cuk of the SETI institute and their colleagues Simon Lock of Harvard University and Sarah Stewart of the University of California, Davis, tried many different scenarios. But the most successful ones involved a moon-forming impact that sent Earth spinning extremely fast — as much as twice the rate predicted by other models. The impact also knocked Earth’s tilt way off, to somewhere between 60 and 80 degrees.

“We already suspected that Earth must have spun especially fast after the impact” Cuk said. “An early high tilt for Earth enables our planet to lose that excess spin more readily.”

The model also suggests that the newly-formed moon started off very close to Earth, but then drifted away — to nearly 15 times its initial distance. As it did so, the sun began to exert a more powerful influence over the moon’s orbit.

According to the researchers, both factors — a highly tilted, fast spinning Earth and an outwardly-migrating moon — contributed to establishing the moon’s current weird orbit. The newborn moon’s orbit most likely tracked Earth’s equator, tilted at a steep 60-80 degree angle that matched Earth’s tilt.

A key finding of the new research is that, if Earth was indeed tilted by more than 60 degrees after the moon formed, the moon could not transition smoothly from Earth’s equatorial plane to the ecliptic plane. Instead, the transition was abrupt and left the moon with a large tilt relative to the ecliptic — much larger than is observed today.

“As the moon moved outward, Earth’s steep tilt made for a more chaotic transition as the sun became a bigger influence,” Cuk said. “Subsequently, and over billions of years, the moon’s tilt slowly decayed down to the five degrees we see today. So today’s five degree tilt is a relic and a signature of a much steeper tilt in the past.”

Hamilton acknowledges that the model doesn’t answer all the remaining questions about the moon’s orbit. But the model’s strength, he says, is that it offers a framework for answering new questions in the future.

“There are many potential paths from the moon’s formation to the Earth-moon system we see today. We’ve identified a few of them, but there are sure to be other possibilities,” Hamilton said. “What we have now is a model that is more probable and works more cleanly than previous attempts. We think this is a significant improvement that gets us closer to what actually happened.”

Cosmic Connection: How Human Cells Are Like Neutron Stars

We humans may be more aligned with the universe than we realize.

According to research published in the journal Physical Review C, neutron stars and cell cytoplasm have something in common: structures that resemble multistory parking garages.

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In 2014, UC Santa Barbara soft condensed-matter physicist Greg Huber and colleagues explored the biophysics of such shapes — helices that connect stacks of evenly spaced sheets — in a cellular organelle called the endoplasmic reticulum (ER). Huber and his colleagues dubbed them Terasaki ramps after their discoverer, Mark Terasaki, a cell biologist at the University of Connecticut.

Huber thought these “parking garages” were unique to soft matter (like the interior of cells) until he happened upon the work of nuclear physicist Charles Horowitz at Indiana University. Using computer simulations, Horowitz and his team had found the same shapes deep in the crust of neutron stars.

“I called Chuck and asked if he was aware that we had seen these structures in cells and had come up with a model for them,” said Huber, the deputy director of UCSB’s Kavli Institute for Theoretical Physics (KITP). “It was news to him, so I realized then that there could be some fruitful interaction.”

The resulting collaboration, highlighted in Physical Review C, explored the relationship between two very different models of matter.

Nuclear physicists have an apt terminology for the entire class of shapes they see in their high-performance computer simulations of neutron stars: nuclear pasta. These include tubes (spaghetti) and parallel sheets (lasagna) connected by helical shapes that resemble Terasaki ramps.

“They see a variety of shapes that we see in the cell,” Huber explained. “We see a tubular network; we see parallel sheets. We see sheets connected to each other through topological defects we call Terasaki ramps. So the parallels are pretty deep.”

However, differences can be found in the underlying physics. Typically matter is characterized by its phase, which depends on thermodynamic variables: density (or volume), temperature and pressure — factors that differ greatly at the nuclear level and in an intracellular context.

“For neutron stars, the strong nuclear force and the electromagnetic force create what is fundamentally a quantum-mechanical problem,” Huber explained. “In the interior of cells, the forces that hold together membranes are fundamentally entropic and have to do with the minimization of the overall free energy of the system. At first glance, these couldn’t be more different.”

Another difference is scale. In the nuclear case, the structures are based on nucleons such as protons and neutrons and those building blocks are measured using femtometers (10-15). For intracellular membranes like the ER, the length scale is nanometers (10-9). The ratio between the two is a factor of a million (10-6), yet these two vastly different regimes make the same shapes.

“This means that there is some deep thing we don’t understand about how to model the nuclear system,” Huber said. “When you have a dense collection of protons and neutrons like you do on the surface of a neutron star, the strong nuclear force and the electromagnetic forces conspire to give you phases of matter you wouldn’t be able to predict if you had just looked at those forces operating on small collections of neutrons and protons.”

The similarity of the structures is riveting for theoretical and nuclear physicists alike. Nuclear physicist Martin Savage was at the KITP when he came across graphics from the new paper on arXiv, a preprint library that posts thousands of physics, mathematics and computer science articles. Immediately his interest was piqued.

“That similar phases of matter emerge in biological systems was very surprising to me,” said Savage, a professor at the University of Washington. “There is clearly something interesting here.”

Co-author Horowitz agreed. “Seeing very similar shapes in such strikingly different systems suggests that the energy of a system may depend on its shape in a simple and universal way,” he said.

Huber noted that these similarities are still rather mysterious. “Our paper is not the end of something,” he said. “It’s really the beginning of looking at these two models.”

Mystery Solved Behind Birth Of Saturn’s Rings

A team of researchers has presented a new model for the origin of Saturn’s rings based on results of computer simulations. The results of the simulations are also applicable to rings of other giant planets and explain the compositional differences between the rings of Saturn and Uranus. The findings were published on October 6 in the online version of Icarus.

saturn

The lead author of the paper is HYODO Ryuki (Kobe University, Graduate School of Science), and co-authors are Professor Sébastien Charnoz (Institute de Physique du Globe/Université Paris Diderot), Professor OHTSUKI Keiji (Kobe University, Graduate School of Science), and Project Associate Professor GENDA Hidenori (Earth-Life Science Institute, Tokyo Institute of Technology).

The giant planets in our solar system have very diverse rings. Observations show that Saturn’s rings are made of more than 95% icy particles, while the rings of Uranus and Neptune are darker and may have higher rock content. Since the rings of Saturn were first observed in the 17th century, investigation of the rings has expanded from earth-based telescopes to spacecraft such as Voyagers and Cassini. However, the origin of the rings was still unclear and the mechanisms that lead to the diverse ring systems were unknown.

The present study focused on the period called the Late Heavy Bombardment that is believed to have occurred 4 billion years ago in our solar system, when the giant planets underwent orbital migration. It is thought that several thousand Pluto-sized (one fifth of Earth’s size) objects from the Kuiper belt existed in the outer solar system beyond Neptune. First the researchers calculated the probability that these large objects passed close enough to the giant planets to be destroyed by their tidal force during the Late Heavy Bombardment. Results showed that Saturn, Uranus and Neptune experienced close encounters with these large celestial objects multiple times.

Next the group used computer simulations to investigate disruption of these Kuiper belt objects by tidal force when they passed the vicinity of the giant planets. The results of the simulations varied depending on the initial conditions, such as the rotation of the passing objects and their minimum approach distance to the planet. However they discovered that in many cases fragments comprising 0.1-10% of the initial mass of the passing objects were captured into orbits around the planet. The combined mass of these captured fragments was found to be sufficient to explain the mass of the current rings around Saturn and Uranus. In other words, these planetary rings were formed when sufficiently large objects passed very close to giants and were destroyed.

The researchers also simulated the long-term evolution of the captured fragments using supercomputers at the National Astronomical Observatory of Japan. From these simulations they found that captured fragments with an initial size of several kilometers are expected to undergo high-speed collisions repeatedly and are gradually shattered into small pieces. Such collisions between fragments are also expected to circularize their orbits and lead to the formation of the rings observed today.

This model can also explain the compositional difference between the rings of Saturn and Uranus. Compared to Saturn, Uranus (and also Neptune) has higher density (the mean density of Uranus is 1.27g cm-3, and 1.64g cm-3 for Neptune, while that of Saturn is 0.69g cm-3). This means that in the cases of Uranus (and Neptune), objects can pass within close vicinity of the planet, where they experience extremely strong tidal forces. (Saturn has a lower density and a large diameter-to-mass ratio, so if objects pass very close they will collide with the planet itself). As a result, if Kuiper belt objects have layered structures such as a rocky core with an icy mantle and pass within close vicinity of Uranus or Neptune, in addition to the icy mantle, even the rocky core will be destroyed and captured, forming rings that include rocky composition. However if they pass by Saturn, only the icy mantle will be destroyed, forming icy rings. This explains the different ring compositions.

These findings illustrate that the rings of giant planets are natural by-products of the formation process of the planets in our solar system. This implies that giant planets discovered around other stars likely have rings formed by a similar process. Discovery of a ring system around an exoplanet has been recently reported, and further discoveries of rings and satellites around exoplanets will advance our understanding of their origin.

NASA Missions Harvest A Passel Of ‘Pumpkin’ Stars

Astronomers using observations from NASA’s Kepler and Swift missions have discovered a batch of rapidly spinning stars that produce X-rays at more than 100 times the peak levels ever seen from the sun. The stars, which spin so fast they’ve been squashed into pumpkin-like shapes, are thought to be the result of close binary systems where two sun-like stars merge.

pumpkin-star

“These 18 stars rotate in just a few days on average, while the sun takes nearly a month,” said Steve Howell, a senior research scientist at NASA’s Ames Research Center in Moffett Field, California, and leader of the team. “The rapid rotation amplifies the same kind of activity we see on the sun, such as sunspots and solar flares, and essentially sends it into overdrive.”

The most extreme member of the group, a K-type orange giant dubbed KSw 71, is more than 10 times larger than the sun, rotates in just 5.5 days, and produces X-ray emission 4,000 times greater than the sun does at solar maximum.

These rare stars were found as part of an X-ray survey of the original Kepler field of view, a patch of the sky comprising parts of the constellations Cygnus and Lyra. From May 2009 to May 2013, Kepler measured the brightness of more than 150,000 stars in this region to detect the regular dimming from planets passing in front of their host stars. The mission was immensely successful, netting more than 2,300 confirmed exoplanets and nearly 5,000 candidates to date. An ongoing extended mission, called K2, continues this work in areas of the sky located along the ecliptic, the plane of Earth’s orbit around the sun.

“A side benefit of the Kepler mission is that its initial field of view is now one of the best-studied parts of the sky,” said team member Padi Boyd, a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who designed the Swift survey. For example, the entire area was observed in infrared light by NASA’s Wide-field Infrared Survey Explorer, and NASA’s Galaxy Evolution Explorer observed many parts of it in the ultraviolet. “Our group was looking for variable X-ray sources with optical counterparts seen by Kepler, especially active galaxies, where a central black hole drives the emissions,” she explained.

Using the X-ray and ultraviolet/optical telescopes aboard Swift, the researchers conducted the Kepler-Swift Active Galaxies and Stars Survey (KSwAGS), imaging about six square degrees, or 12 times the apparent size of a full moon, in the Kepler field.

“With KSwAGS we found 93 new X-ray sources, about evenly split between active galaxies and various types of X-ray stars,” said team member Krista Lynne Smith, a graduate student at the University of Maryland, College Park who led the analysis of Swift data. “Many of these sources have never been observed before in X-rays or ultraviolet light.”

For the brightest sources, the team obtained spectra using the 200-inch telescope at Palomar Observatory in California. These spectra provide detailed chemical portraits of the stars and show clear evidence of enhanced stellar activity, particularly strong diagnostic lines of calcium and hydrogen.

The researchers used Kepler measurements to determine the rotation periods and sizes for 10 of the stars, which range from 2.9 to 10.5 times larger than the sun. Their surface temperatures range from somewhat hotter to slightly cooler than the sun, mostly spanning spectral types F through K. Astronomers classify the stars as subgiants and giants, which are more advanced evolutionary phases than the sun’s caused by greater depletion of their primary fuel source, hydrogen. All of them eventually will become much larger red giant stars.

Forty years ago, Ronald Webbink at the University of Illinois, Urbana-Champaign noted that close binary systems cannot survive once the fuel supply of one star dwindles and it starts to enlarge. The stars coalesce to form a single rapidly spinning star initially residing in a so-called “excretion” disk formed by gas thrown out during the merger. The disk dissipates over the next 100 million years, leaving behind a very active, rapidly spinning star.

Howell and his colleagues suggest that their 18 KSwAGS stars formed by this scenario and have only recently dissipated their disks. To identify so many stars passing through such a cosmically brief phase of development is a real boon to stellar astronomers.

“Webbink’s model suggests we should find about 160 of these stars in the entire Kepler field,” said co-author Elena Mason, a researcher at the Italian National Institute for Astrophysics Astronomical Observatory of Trieste. “What we have found is in line with theoretical expectations when we account for the small portion of the field we observed with Swift.”

The team has already extended their Swift observations to additional fields mapped by the K2 mission.

Insights Into Giant Impacts On Moon, Earth And Mars

New results from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission are providing insights into the huge impacts that dominated the early history of Earth’s moon and other solid worlds, like Earth, Mars, and the satellites of the outer solar system.

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In two papers, published this week in the journal Science, researchers examine the origins of the moon’s giant Orientale impact basin. The research helps clarify how the formation of Orientale, approximately 3.8 billion years ago, affected the moon’s geology.

Located along the moon’s southwestern limb — the left-hand edge as seen from Earth — Orientale is the largest and best-preserved example of what’s known as a “multi-ring basin.” Impact craters larger than about 180 miles (300 kilometers) in diameter are referred to as basins. With increasing size, craters tend to have increasingly complex structures, often with multiple concentric, raised rings. Orientale is about 580 miles (930 kilometers) wide and has three distinct rings, which form a bullseye-like pattern.

Multi-ring basins are observed on many of the rocky and icy worlds in our solar system, but until now scientists had not been able to agree on how their rings form. What they needed was more information about the crater’s structure beneath the surface, which is precisely the sort of information contained in gravity science data collected during the GRAIL mission.

The powerful impacts that created basins like Orientale played an important role in the early geologic history of our moon. They were extremely disruptive, world-altering events that caused substantial fracturing, melting and shaking of the young moon’s crust. They also blasted out material that fell back to the surface, coating older features that were already there; scientists use this layering of ejected material to help determine the age of lunar features as they work to unravel the moon’s complex history.

The Importance of Orientale

Because scientists realized that Orientale could be quite useful in understanding giant impacts, they gave special importance to observing its structure near the end of the GRAIL mission. The orbit of the mission’s two probes was lowered so they passed less than 1.2 miles (2 kilometers) above the crater’s mountainous rings.

“No other planetary exploration mission has made gravity science observations this close to the moon. You could have waved to the twin spacecraft as they flew overhead if you stood at the ring’s edge,” said Sami Asmar, GRAIL project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.

Of particular interest to researchers has been the size of the initial crater that formed during the Orientale impact. With smaller impacts, the initial crater is left behind, and many characteristics of the event can be inferred from the crater’s size. Various past studies have suggested each of Orientale’s three rings might be the remnant of the initial crater.

In the first of the two new studies, scientists teased out the size of the transient crater from GRAIL’s gravity field data. Their analysis shows that the initial crater was somewhere between the size of the basin’s two innermost rings.

“We’ve been able to show that none of the rings in Orientale basin represent the initial, transient crater,” said GRAIL Principal Investigator Maria Zuber of the Massachusetts Institute of Technology in Cambridge, lead author of the first paper. “Instead, it appears that, in large impacts like the one that formed Orientale, the surface violently rebounds, obliterating signs of the initial impact.”

The analysis also shows that the impact excavated at least 816,000 cubic miles (3.4 million cubic kilometers) of material — 153 times the combined volume of the Great Lakes.

“Orientale has been an enigma since the first gravity observations of the moon, decades ago,” said Greg Neumann, a co-author of the paper at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We are now able to resolve the individual crustal components of the bullseye gravity signature and correlate them with computer simulations of the formation of Orientale.”

Reproducing the Rings

The second study describes how scientists successfully simulated the formation of Orientale to reproduce the crater’s structure as observed by GRAIL. These simulations show, for the first time, how the rings of Orientale formed, which is likely similar for multi-ring basins in general.

“Because our models show how the subsurface structure is formed, matching what GRAIL has observed, we’re confident we’ve gained understanding of the formation of the basin close to 4 billion years ago,” said Brandon Johnson of Brown University, Providence, Rhode Island, lead author of the second paper.

The results also shed light on another moon mystery: Giant impacts like Orientale should have dredged up deep material from the moon’s mantle, but instead, the composition of the crater’s surface is the same as that of the lunar crust. So, scientists have wondered, where did the mantle material go?

The simulation shows that the deep, initial crater quickly collapses, causing material around the outside to flow inward, and covering up the exposed mantle rock.

The new GRAIL insights about Orientale suggest that other ringed basins, invisible in images, could be discovered by their gravity signature. This may include ringed basins hidden beneath lunar maria — the large, dark areas of solidified lava that include the Sea of Tranquility and the Sea of Serenity.

“The data set we obtained with GRAIL is incredibly rich,” said Zuber. “There are many hidden wonders on the moon that we’ll be uncovering for years to come.”

The twin GRAIL probes were launched in 2011. The mission concluded in 2012.

Unexpected Giant Glowing Halos Discovered Around Distant Quasars

An international collaboration of astronomers, led by a group at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, has used the unrivalled observing power of MUSE on the Very Large Telescope (VLT) at ESO’s Paranal Observatory to study gas around distant active galaxies, less than two billion years after the Big Bang. These active galaxies, called quasars, contain supermassive black holes in their centres, which consume stars, gas, and other material at an extremely high rate. This, in turn, causes the galaxy centre to emit huge amounts of radiation, making quasars the most luminous and active objects in the Universe.

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The study involved 19 quasars, selected from among the brightest that are observable with MUSE. Previous studies have shown that around 10% of all quasars examined were surrounded by halos, made from gas known as the intergalactic medium. These halos extend up to 300,000 light-years away from the centres of the quasars. This new study, however, has thrown up a surprise, with the detection of large halos around all 19 quasars observed — far more than the two halos that were expected statistically. The team suspects this is due to the vast increase in the observing power of MUSE over previous similar instruments, but further observations are needed to determine whether this is the case.

“It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample. So there is still a lot to learn; we are just at the beginning of a new era of discoveries,” says lead author Elena Borisova, from the ETH Zurich.

The original goal of the study was to analyse the gaseous components of the Universe on the largest scales; a structure sometimes referred to as the cosmic web, in which quasars form bright nodes [1]. The gaseous components of this web are normally extremely difficult to detect, so the illuminated halos of gas surrounding the quasars deliver an almost unique opportunity to study the gas within this large-scale cosmic structure.

The 19 newly-detected halos also revealed another surprise: they consist of relatively cold intergalactic gas — approximately 10,000 degrees Celsius. This revelation is in strong disagreement with currently accepted models of the structure and formation of galaxies, which suggest that gas in such close proximity to galaxies should have temperatures upwards of a million degrees.

The discovery shows the potential of MUSE for observing this type of object [2]. Co-author Sebastiano Cantalupo is very excited about the new instrument and the opportunities it provides: “We have exploited the unique capabilities of MUSE in this study, which will pave the way for future surveys. Combined with a new generation of theoretical and numerical models, this approach will continue to provide a new window on cosmic structure formation and galaxy evolution.”