The patent process is a very significant process, it's not like an academic peer review where everyone hides behind an anonymous review, and it’s all out in the open. This is a proper, professional way of establishing prior ownership done by professionals in the patent office, and in order to publish my patent application, they had to first carry out a thorough examination of the physics in order to establish that the invention does not contravene the laws of physics.

This is pretty significant, because it enables you to easily manufacture these things, and we want to produce thousands of them. The patent makes the construction of a viable superconducting thruster easier, and it will produce a lot of thrust.

"We expected to find these waves in the lower levels because we see them in the upper levels, and we thought that they rose up through the cloud from the surface," co-author Ricardo Hueso of the University of the Basque Country in Bilbao, Spain, in the statement. "It's an unexpected result for sure, and we'll all need to revisit our models of Venus to explore its meaning."

Scientists have long observed an apparent gradient in the cosmic microwave background but have been unable to determine how much is real and how much is perceived. USC Dornsife researchers appear to have found a way to an answer.

A remnant of the Big Bang, the cosmic microwave background appears to harbor a gradient across the universe, a feature that has puzzled cosmologists for decades [Credit: Matthew Savino]

Observed from Earth, the universe appears a bit hotter at one end than the other, at least in terms of the cosmic microwave background (CMB). But the question plaguing cosmologists is whether that imbalance in the CMB is real or a result of the Doppler effect.

USC Dornsife scientists Siavash Yasini and Elena Pierpaoli may have found a way to nail down an answer.

Made most famous perhaps by Edwin Hubble, who used it to show that the universe is expanding, the Doppler effect is the apparent shift in the frequency of electromagnetic waves due to the motion of bodies traveling swiftly through space. Waves such as electromagnetic radiation—light waves, X-rays, microwaves, etc.—appear to shift in energy, with those moving toward an observer appearing to be higher in energy, or hotter, than they really are. The opposite is true for waves moving away from the observer, which appear colder.

Scientists looking at the sky see space trailing behind Earth appearing colder than space up ahead, but it's not clear if that's only the Doppler effect or an observation of a true difference in CMB temperature. It's a puzzle that has persisted for decades.

Because the CMB is leftover energy from the Big Bang—when the entire universe exploded outward from a single point—cosmologists have assumed it is dispersed evenly. The appearance of two poles in the universe, one warmer than the other, must therefore be a result of the Doppler effect, a result of the solar system careening through space.

"We think that one side of the CMB only looks hotter because we are moving towards it, and the opposite side looks colder because we are moving away from it," said Yasini, a Ph.D. student in physics and astronomy.

Astrophysicists measuring the solar system's velocity relative to the CMB adjust their calculations based on this assumption, as do cosmologists studying the Big Bang and conditions shortly after.

But this might be a mistake after all.

"If there is an intrinsic dipole in the CMB—that is, if one side of the sky is actually partially hotter than the opposite side—the velocity we assign the solar system with respect to the CMB would be incorrect," Yasini said. This would affect how scientists measure the speed of distant objects such as galaxies, and theories about what happened moments after the Big Bang could be shaken.

Running calculations for a different but related study, Yasini and Professor of Physics and Astronomy Pierpaoli, who is Yasini's graduate school mentor, found an interesting detail: The frequency spectrum of the CMB averaged across the sky will differ if the dipole is real and not just a result of the Doppler effect.

In other words, if the CMB is, in fact, hotter at one end of the universe than the other, the average temperature measured across the whole sky will be slightly different than if the CMB is actually uniform.

Yasini and Pierpaoli's findings will allow cosmologists undertaking the next generation of CMB surveys to determine the nature of the CMB dipole for the first time ever, solving the puzzle.

"Now that we have a mathematical basis for finding an answer, it just remains to make the observations," Pierpaoli said.

If it turns out a portion of the dipole is real and not just a result of the Doppler effect, astrophysicists and astronomers will have to recalibrate all of their measurements to get a more accurate view of the observable universe.

Just as important, cosmologists studying the Big Bang and conditions in the very early universe will have new directions to explore to understand how and why the CMB is dispersed unevenly, and how the universe came to be as it now is.

Author: Darrin S. Joy | Source: University of Southern California [March 07, 2018]

What if there is a deeper reality out there? What if our universe is an illusion? What if we are living in a hologram? Cue Twilight Zone music.

Credit: TU Wien

Or, alternatively, ask associate professor of physics Matthew Headrick about his research. Headrick works on one of the most cutting-edge theories in theoretical physics—the holographic principle. It holds that the universe is a three-dimensional image projected off a two-dimensional surface, much like a hologram emerges from a sheet of photographic film.

"In my view, the discovery of holographic entanglement and its generalizations has been one of the most exciting developments in theoretical physics in this century so far," Headrick said. "What other new concepts are waiting to be discovered, and what other unexpected connections? We can't wait to find out."

Since 2016, Headrick has served as deputy director of the "It from Qubit: Quantum Fields, Gravity and Information" project, an international effort by 18 scientists and their labs to determine whether the holographic principle is correct. It is funded by a 4-year, $10-million grant from the New York-based Simons Foundation.

If Headrick and his colleagues can prove the holographic principle, they will have taken a major step toward achieving the holy grail in theoretical physics, a grand unified theory that can explain all the laws and principles governing reality. "We're not there yet," Headrick said, "but we're making progress."

Let's break down the holographic principle step-by-step:

Information

We'll start small, very small. It's long been thought that the universe at its most fundamental level is made up of subatomic particles like electrons or quarks. But now physicists believe those particles are made up of something even smaller—information.

When physicists talk about information, they mean the data that describe physical phenomena. The mass of an object, the direction of the spin of an electron, and e=mc^2 are all units of information.

If you gathered all the information that's out there, you would have the complete instruction booklet for building everything in our universe.

Qubits

The tiniest levels of the universe are governed by the laws of quantum mechanics. Here things start to get very weird and counterintuitive.

Units of information in the realm of quantum mechanics are called qubits.

Headrick studies the quantum entanglement of qubits, a very strange phenomenon unique to the realm of quantum mechanics.

Suppose you have two qubits whose values can be either 1 or 0. When the qubits are entangled, their values become correlated. When you measure the first qubit, its value might turn out to be 0. Check the other qubit, its value might be 0, too. But what if the first qubit has a value of 1? The second qubit's value could also change to 1.

It's as if the qubits communicate with each other, with the first telling the second, "Hey, this physicist over here just found out I'm a 1. You better be a 1, too." Amazingly and bizarrely, this communication can happen over vast distances with messages seemingly relayed faster than the speed of light.

Qubits are flat

In most cases, when you drop an object into a jar—we'll use a jelly bean—it will fall inside and take up space. Put in another jelly bean, the amount of unfilled space shrinks and the volume of the jelly beans increases.

It doesn't work this way with qubits. Qubits won't fall into the jar but instead spread out on a surface. Add a qubit, it will adhere to the side of the jar. Add another qubit, it will do the same. Increasing the number of qubits doesn't increase the volume. Instead, it increases the surface area the qubits take up.

More and more qubits spreading out across a flat surface—this is how you get the two-dimensional plane described by the holographic principle.

So how do you get three dimensions?

Once you move beyond the realm of the teeny-tiny, the laws of quantum mechanics no longer work. Strange as it sounds, on the macrocosmic level, you need a different set of laws of physics to explain what's going on.

Enter Einstein's theory of relativity. To calculate cosmic events like the path followed by light or the orbit of Mercury around the sun, you need the theory of relativity.

The building blocks of relativity are also units of information. Now though, they're called bits.

And bits behave in a way that's much more familiar to us. They exist in three dimensions.

So how do you get a hologram?

Let's go back to that two-dimensional surface covered with entangled qubits. Since the value of a qubit changes depending on the value of its entangled pair, there's a degree of indeterminacy built into the system. If you haven't yet measured the first qubit, you can't be sure about the second. The amount of uncertainty in any given system is called its entropy.

As qubits become entangled and disentangled, the level of entropy rises and falls. You wind up with fields of entropy in a constantly changing state.

The holographic principle holds that our three-dimensional world is a representation or projection of all this activity taking place on a two-dimensional surface full of qubits.

Putting it all together

It's always bothered physicists that there is one set of rules for the microcosmic, quantum mechanics, and another for the macrocosmic, the theory of relativity. It doesn't make sense that there should be two different and incompatible groups of mathematical formulas at work in our universe. Physicists assume there must be some way to bring them into harmony.

So therein lies the central question for Headrick and his colleagues: Starting in the two-dimensional realm of qubits and quantum mechanics and then scaling up in size, how precisely do we wind up with bits and relativity? It's a matter of constructing a single mathematical model that explains the transformation.

Figure it out and you'll have solved one of the biggest mysteries in theoretical physics. From the tiniest to the largest phenomenon, we'll have a unified theory of reality.

Right now the holographic principle remains an unproven theory. Where it will lead next is an open question. Odds are though, it'll be stranger than anything yet imagined in science fiction.

Author: Lawrence Goodman | Source: Brandeis University [March 06, 2018]

Quantum mechanics is the branch of physics governing the sometimes-strange behavior of the tiny particles that make up our universe. Equations describing the quantum world are generally confined to the subatomic realm -- the mathematics relevant at very small scales is not relevant at larger scales, and vice versa. However, a surprising new discovery from a Caltech researcher suggests that the Schrödinger Equation -- the fundamental equation of quantum mechanics -- is remarkably useful in describing the long-term evolution of certain astronomical structures.

An artist's impression of research presented in Batygin (2018), MNRAS 475, 4. Propagation of waves through an astrophysical disk can be understood using Schrödinger's equation -- a cornerstone of quantum mechanics [Credit: James Tuttle Keane, California Institute of Technology]

The work, done by Konstantin Batygin, a Caltech assistant professor of planetary science and Van Nuys Page Scholar, is described in a paper appearing in the Monthly Notices of the Royal Astronomical Society.

Massive astronomical objects are frequently encircled by groups of smaller objects that revolve around them, like the planets around the sun. For example, supermassive black holes are orbited by swarms of stars, which are themselves orbited by enormous amounts of rock, ice, and other space debris. Due to gravitational forces, these huge volumes of material form into flat, round disks. These disks, made up of countless individual particles orbiting en masse, can range from the size of the solar system to many light-years across.

Astrophysical disks of material generally do not retain simple circular shapes throughout their lifetimes. Instead, over millions of years, these disks slowly evolve to exhibit large-scale distortions, bending and warping like ripples on a pond. Exactly how these warps emerge and propagate has long puzzled astronomers, and even computer simulations have not offered a definitive answer, as the process is both complex and prohibitively expensive to model directly.

While teaching a Caltech course on planetary physics, Batygin (the theorist behind the proposed existence of Planet Nine) turned to an approximation scheme called perturbation theory to formulate a simple mathematical representation of disk evolution. This approximation, often used by astronomers, is based upon equations developed by the 18th-century mathematicians Joseph-Louis Lagrange and Pierre-Simon Laplace. Within the framework of these equations, the individual particles and pebbles on each particular orbital trajectory are mathematically smeared together. In this way, a disk can be modeled as a series of concentric wires that slowly exchange orbital angular momentum among one another.

As an analogy, in our own solar system one can imagine breaking each planet into pieces and spreading those pieces around the orbit the planet takes around the sun, such that the sun is encircled by a collection of massive rings that interact gravitationally. The vibrations of these rings mirror the actual planetary orbital evolution that unfolds over millions of years, making the approximation quite accurate.

Using this approximation to model disk evolution, however, had unexpected results.

"When we do this with all the material in a disk, we can get more and more meticulous, representing the disk as an ever-larger number of ever-thinner wires," Batygin says. "Eventually, you can approximate the number of wires in the disk to be infinite, which allows you to mathematically blur them together into a continuum. When I did this, astonishingly, the Schrödinger Equation emerged in my calculations."

The Schrödinger Equation is the foundation of quantum mechanics: It describes the non-intuitive behavior of systems at atomic and subatomic scales. One of these non-intuitive behaviors is that subatomic particles actually behave more like waves than like discrete particles -- a phenomenon called wave-particle duality. Batygin's work suggests that large-scale warps in astrophysical disks behave similarly to particles, and the propagation of warps within the disk material can be described by the same mathematics used to describe the behavior of a single quantum particle if it were bouncing back and forth between the inner and outer edges of the disk.

The Schrödinger Equation is well studied, and finding that such a quintessential equation is able to describe the long-term evolution of astrophysical disks should be useful for scientists who model such large-scale phenomena. Additionally, adds Batygin, it is intriguing that two seemingly unrelated branches of physics -- those that represent the largest and the smallest of scales in nature -- can be governed by similar mathematics.

"This discovery is surprising because the Schrödinger Equation is an unlikely formula to arise when looking at distances on the order of light-years," says Batygin. "The equations that are relevant to subatomic physics are generally not relevant to massive, astronomical phenomena. Thus, I was fascinated to find a situation in which an equation that is typically used only for very small systems also works in describing very large systems."

"Fundamentally, the Schrödinger Equation governs the evolution of wave-like disturbances." says Batygin. "In a sense, the waves that represent the warps and lopsidedness of astrophysical disks are not too different from the waves on a vibrating string, which are themselves not too different from the motion of a quantum particle in a box. In retrospect, it seems like an obvious connection, but it's exciting to begin to uncover the mathematical backbone behind this reciprocity."

Source: California Institute of Technology [March 05, 2018]

A research team of multiple institutes, including the National Astronomical Observatory of Japan and University of Tokyo, released an unprecedentedly wide and sharp dark matter map based on the newly obtained imaging data by Hyper Suprime-Cam on the Subaru Telescope.

Hyper Suprime-Cam image of a location with a highly significant dark matter halo detected through the weak gravitational  lensing technique. This halo is so massive that some of the background (blue) galaxies are stretched tangentially  around the center of the halo. This is called strong lensing [Credit: NAOJ]

The dark matter distribution is estimated by the weak gravitational lensing technique. The team located the positions and lensing signals of the dark matter halos and found indications that the number of halos could be inconsistent with what the simplest cosmological model suggests. This could be a new clue to understanding why the expansion of the Universe is accelerating.

Mystery of the accelerated Universe

In the 1930's, Edwin Hubble and his colleagues discovered the expansion of the Universe. This was a big surprise to most of the people who believed that the Universe stayed the same throughout eternity. A formula relating matter and the geometry of space-time was required in order to express the expansion of the Universe mathematically. Coincidentally, Einstein had already developed just such a formula. Modern cosmology is based on Einstein's theory for gravity.

2 dimensional dark matter map estimated by weak lensing technique. The dark matter is concentrated in dense clumps.  We can identify massive dark matter halos (indicated by oranges circles). The area shown in this figure  is approximately 30 square degrees (a total of 160 square degrees were observed this time)  [Credit: NAOJ/University of Tokyo]

It had been thought that the expansion is decelerating over time because the contents of the Universe (matter) attract each other. But in the late 1990's, it was found that the expansion has been accelerating since about 8 Giga years ago. This was another big surprise which earned the astronomers who found the expansion a Nobel Prize in 2011. To explain the acceleration, we have to consider something new in the Universe which repels the space.

The simplest resolution is to put the cosmological constant back into Einstein's equation. The cosmological constant was originally introduced by Einstein to realize a static universe, but was abandoned after the discovery of the expansion of the Universe. The standard cosmological model (called LCDM) incorporates the cosmological constant. LCDM is supported by many observations, but the question of what causes the acceleration still remains. This is one of the biggest problems in modern cosmology.

Wide and deep imaging survey using Hyper Suprime-Cam

The team is leading a large scale imaging survey using Hyper Suprime-Cam (HSC) to probe the mystery of the accelerating Universe. The key here is to examine the expansion history of the Universe very carefully.

Expansion history of the Universe. The blue line shows what was believed to be likely in the early days of cosmology.  Later this cosmological model fell out of favor because it predicts a higher growth rate and more structures, inconsistent  with the observed galaxy distribution. Thus a much lighter Universe model was proposed which is shown by the red line.  This light model also solved the so called "age problem," the existence of globular clusters older than the age of the  Universe predicted by the blue track. But both the blue and red lines conflict with the inflation cosmology. Later when  the acceleration of the Universe was discovered, LCDM represented by the green track, was adopted as the  most likely model. Thanks to the addition of the cosmological constant, LCDM becomes consistent  with the inflation model [Credit: NAOJ]

In the early Universe, matter was distributed almost but not quite uniformly. There were slight fluctuations in the density which can now be observed through the temperature fluctuations of the cosmic microwave background. These slight matter fluctuations evolved over cosmic time because of the mutual gravitational attraction of matter, and eventually the large scale structure of the present day Universe become visible. It is known that the growth rate of the structure strongly depends on how the Universe expands. For example, if the expansion rate is high, it is hard for matter to contract and the growth rate is suppressed. This means that the expansion history can be probed inversely through the observation of the growth rate.

It is important to note that growth rate cannot be probed well if we only observe visible matter (stars and galaxies). This is because we now know that nearly 80 % of the matter is an invisible substance called dark matter. The team adopted the 'weak gravitation lensing technique.' The images of distant galaxies are slightly distorted by the gravitational field generated by the foreground dark matter distribution. Analysis of the systematic distortion enables us to reconstruct the foreground dark matter distribution.

An example of 3D distribution of dark matter reconstructed via tomographic methods using the weak lensing technique  combined with the redshift estimates of the background galaxies [Credit: University of Tokyo/NAOJ]

This technique is observationally very demanding because the distortion of each galaxy is generally very subtle. Precise shape measurements of faint and apparently small galaxies are required. This motivated the team to develop Hyper Suprime-Cam. They have been carrying out a wide field imaging survey using Hyper Suprime-Cam since March 2014. At this writing in February 2018, 60 % of the survey has been completed.

Unprecedentedly wide and sharp dark matter map

The team is now presenting the dark matter map based on the imaging data taken by April 2016. This is only 11 % of the planned final map, but it is already unprecedentedly wide. There has never been such a sharp dark matter map covering such a wide area.

Number of dark matter halos versus their lensing signal strength (black histogram) and number count expected from  LCDM and the most recent CMB observation by the Planck satellite [Credit: NAOJ/University of Tokyo]

Imaging observations are made through five different color filters. By combining these color data, it is possible to make a crude estimate of the distances to the faint background galaxies (called photometric redshift). At the same time, the lensing efficiency becomes most prominent when the lens is located directly between the distant galaxy and the observer. Using the photometric redshift information, galaxies are grouped into redshift bins. Using this grouped galaxy sample, dark matter distribution is reconstructed using tomographic methods and thus the 3D distribution can be obtained. Data for 30 square degrees are used to reconstruct the redshift range between 0.1 (~1.3 G light-years) and 1.0 (~8 G light-years). At the redshift of 1.0, the angular span corresponds to 1.0 G x 0.25 G light-years. This 3D dark matter mass map is also quite new. This is the first time the increase in the number of dark matter halos over time can be seen observationally.

What the dark matter halo count suggests and future prospects

The team counted the number of dark matter halos whose lensing signal is above a certain threshold. This is one of the simplest measurements of the growth rate. It is suggested that the number count of the dark matter halos is less than what is expected from LCDM. This could indicate there is a flaw in LCDM and that we might have to consider an alternative rather than the simple cosmological constant (Note 1).


The statistical significance is, however, still limited as the large error bars suggest. There has been no conclusive evidence to reject LCDM, but many astronomers are interested in testing LCDM because discrepancies can be a useful probe to unlock the mystery of the accelerating Universe. Further observation and analysis are needed to confirm the discrepancy with higher significance. There are some other probes of the growth rate and such analysis are also underway (e.g. angular correlation of galaxy shapes) in the team to check the validity of standard LCDM.

Note 1: Empty space is known to have energy caused by quantum effects and this is one candidate for the source of the cosmological constant. However, the energy density of the cosmological constant is many orders of magnitude weaker than what would be predicted based on this "vacuum energy" and it is hard to reconcile the discrepancy. Astronomers started to consider the existence of some other physical mechanism to explain the energy density, that concept is now called dark energy. The energy density can change over time in this generalization. If the dark energy was stronger in the past, the acceleration would have been more significant and suppressed the growth rate. This would result in fewer dark matter halos.

The study is published in Publications of the Astronomical Society of Japan.

Source: National Institutes of Natural Sciences [March 02, 2018]

In 1929 Edwin Hubble surprised many people -- including Albert Einstein -- when he showed that the universe is expanding. Another bombshell came in 1998 when two teams of astronomers proved that cosmic expansion is actually speeding up due to a mysterious property of space called dark energy. This discovery provided the first evidence of what is now the reigning model of the universe: "Lambda-CDM," which says that the cosmos is approximately 70 percent dark energy, 25 percent dark matter and 5 percent "normal" matter (everything we've ever observed).

This composite of two astrophysics simulations shows a Type Ia supernova (purple disc) expanding over different  microlensing magnification patterns (colored fields). Because individual stars in the lensing galaxy can significantly change  the brightness of a lensed event regions of the supernova can experience varying amounts of brightening and dimming, which scientists believed would be a problem for cosmologists measuring time delays. Using detailed computer simulations at NERSC, astrophysicists showed that this would have a small effect on time-delay cosmology [Credit: Danny Goldstein, UC Berkeley]

Until 2016, Lambda-CDM agreed beautifully with decades of cosmological data. Then a research team used the Hubble Space Telescope to make an extremely precise measurement of the local cosmic expansion rate. The result was another surprise: the researchers found that the universe was expanding a little faster than Lambda-CDM and the Cosmic Microwave Background (CMB), relic radiation from the Big Bang, predicted. So it seems something's amiss -- could this discrepancy be a systematic error, or possibly new physics?

Astrophysicists at Lawrence Berkeley National Laboratory (Berkeley Lab) and the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK believe that strongly lensed Type Ia supernovae are the key to answering this question. And in a new Astrophysical Journal paper, they describe how to control "microlensing," a physical effect that many scientists believed would be a major source of uncertainty facing these new cosmic probes. They also show how to identify and study these rare events in real time.

"Ever since the CMB result came out and confirmed the accelerating universe and the existence of dark matter, cosmologists have been trying to make better and better measurements of the cosmological parameters, shrink the error bars," says Peter Nugent, an astrophysicist in Berkeley Lab's Computational Cosmology Center (C3) and co-author on the paper. "The error bars are now so small that we should be able to say 'this and this agree,' so the results presented in 2016 introduced a big tension in cosmology. Our paper presents a path forward for determining whether the current disagreement is real or whether it's a mistake."

Better Distance Markers Shed Brighter Light on Cosmic History

The farther away an object is in space, the longer its light takes to reach Earth. So the farther out we look, the further back in time we see. For decades, Type Ia supernovae have been exceptional distance markers because they are extraordinarily bright and similar in brightness no matter where they sit in the cosmos. By looking at these objects, scientists discovered that dark energy is propelling cosmic expansion.

But last year an international team of researchers found an even more reliable distance marker -- the first-ever strongly lensed Type Ia supernova. These events occur when the gravitational field of a massive object -- like a galaxy -- bends and refocuses passing light from a Type Ia event behind it. This "gravitational lensing" causes the supernova's light to appear brighter and sometimes in multiple locations, if the light rays travel different paths around the massive object.

Because different routes around the massive object are longer than others, light from different images of the same Type Ia event will arrive at different times. By tracking time-delay between the strongly lensed images, astrophysicists believe they can get a very precise measurement of the cosmic expansion rate.

"Strongly lensed supernovae are much rarer than conventional supernovae -- they're one in 50,000. Although this measurement was first proposed in the 1960's, it has never been made because only two strongly lensed supernovae have been discovered to date, neither of which were amenable to time delay measurements," says Danny Goldstein, a UC Berkeley graduate student and lead author on the new Astrophysical Journal paper.

After running a number of computationally intensive simulations of supernova light at the National Energy Research Scientific Computing Center (NERSC), a Department of Energy Office of Science User Facility located at Berkeley Lab, Goldstein and Nugent suspect that they'll be able to find about 1,000 of these strongly lensed Type Ia supernovae in data collected by the upcoming Large Synoptic Survey Telescope (LSST) -- about 20 times more than previous expectations. These results are the basis of their new paper in the Astrophysical Journal.

"With three lensed quasars -- cosmic beacons emanating from massive black holes in the centers of galaxies -- collaborators and I measured the expansion rate to 3.8 percent precision. We got a value higher than the CMB measurement, but we need more systems to be really sure that something is amiss with the standard model of cosmology, " says Thomas Collett, an astrophysicist at the University of Portsmouth and a co-author on the new Astrophysical Journal paper. "It can take years to get a time delay measurement with quasars, but this work shows we can do it for supernovae in months. One thousand lensed supernovae will let us really nail down the cosmology."

In addition to identifying these events, the NERSC simulations also helped them prove that strongly lensed Type Ia supernovae can be very accurate cosmological probes.

"When cosmologists try to measure time delays, the problem they often encounter is that individual stars in the lensing galaxy can distort the light curves of the different images of the event, making it harder to match them up," says Goldstein. "This effect, known as 'microlensing,' makes it harder to measure accurate time delays, which are essential for cosmology."

But after running their simulations, Goldstein and Nugent found microlensing did not change the colors of strongly lensed Type Ia supernova in their early phases. So researchers can subtract the unwanted effects of microlensing by working with colors instead of light curves. Once these undesirable effects are subtracted, scientists will be able to easily match the light curves and make accurate cosmological measurements.

They came to this conclusion by modeling the supernovae using the SEDONA code, which was developed with funding from two DOE Scientific Discovery through Advanced Computing (SciDAC) Institutes to calculate light curves, spectra and polarization of aspherical supernova models.

"In the early 2000s DOE funded two SciDAC projects to study supernova explosions, we basically took the output of those models and passed them through a lensing system to prove that the effects are achromatic," says Nugent.

"The simulations give us a dazzling picture of the inner workings of a supernova, with a level of detail that we could never know otherwise," says Daniel Kasen, an astrophysicist in Berkeley Lab's Nuclear Science Division, and a co-author on the paper. "Advances in high performance computing are finally allowing us to understand the explosive death of stars, and this study shows that such models are needed to figure out new ways to measure dark energy."

Taking Supernova Hunting to the Extreme

When LSST begins full survey operations in 2023, it will be able to scan the entire sky in only three nights from its perch on the Cerro Pachón ridge in north-central Chile. Over its 10-year mission, LSST is expected to deliver over 200 petabytes of data. As part of the LSST Dark Energy Science Collaboration, Nugent and Goldstein hope that they can run some of this data through a novel supernova-detection pipeline, based at NERSC.

For more than a decade, Nugent's Real-Time Transient Detection pipeline running at NERSC has been using machine learning algorithms to scour observations collected by the Palomar Transient Factor (PTF) and then the Intermediate Palomar Transient Factory (iPTF) -- searching every night for "transient" objects that change in brightness or position by comparing the new observations with all of the data collected from previous nights. Within minutes after an interesting event is discovered, machines at NERSC then trigger telescopes around the globe to collect follow-up observations. In fact, it was this pipeline that revealed the first-ever strongly lensed Type Ia supernova earlier this year.

"What we hope to do for the LSST is similar to what we did for Palomar, but times 100," says Nugent. "There's going to be a flood of information every night from LSST. We want to take that data and ask what do we know about this part of the sky, what's happened there before and is this something we're interested in for cosmology?"

He adds that once researchers identify the first light of a strongly lensed supernova event, computational modeling could also be used to precisely predict when the next of the light will appear. Astronomers can use this information to trigger ground- and space-based telescopes to follow up and catch this light, essentially allowing them to observe a supernova seconds after it goes off.

"I came to Berkeley Lab 21 years ago to work on supernova radiative-transfer modeling and now for the first time we've used these theoretical models to prove that we can do cosmology better," says Nugent. "It's exciting to see DOE reap the benefits of investments in computational cosmology that they started making decades ago."

Author: Linda Vu | Source: Lawrence Berkeley National Laboratory [March 01, 2018]

"The collapse of the galaxy and the formation of a million-solar-mass black hole takes 100,000 years—a blip in cosmic time," says study co-author Zoltan Haiman, an astronomy professor at Columbia University. "A few hundred-million years later, it has grown into a billion-solar-mass supermassive black hole. This is much faster than we expected."

"The nearby galaxy can't be too close, or too far away, and like the Goldilocks principle, too hot or too cold," said study coauthor John Wise, an associate astrophysics professor at Georgia Tech.

"The nearby galaxy can't be too close, or too far away, and like the Goldilocks principle, too hot or too cold," said study coauthor John Wise, an associate astrophysics professor at Georgia Tech.

"Understanding how supermassive black holes form tells us how galaxies, including our own, form and evolve, and ultimately, tells us more about the universe in which we live," said Regan, at Dublin City University.

Long ago, about 400,000 years after the beginning of the universe (the Big Bang), the universe was dark. There were no stars or galaxies, and the universe was filled primarily with neutral hydrogen gas.

This artist's rendering shows the universe's first, massive, blue stars embedded in gaseous filaments, with the cosmic microwave background just visible at the edges. Using radio observations of the distant universe, NSF-funded researchers Judd Bowman of Arizona State University, Alan Rogers of MIT and their colleagues discovered the influence of such early stars on primordial gas. Although they can't directly see the light from the massive stars, Bowman's team was able to infer their presence from dimming of the cosmic microwave background (CMB), a result of the gaseous filaments absorbing the stars' UV light. The CMB is dimmer than expected, indicating that the filaments may have been colder than expected, possibly from interactions with dark matter [Credit: N.R.Fuller, National Science Foundation]

Then, for the next 50-100 million years, gravity slowly pulled the densest regions of gas together until ultimately the gas collapsed in some places to form the first stars.

What were those first stars like and when did they form? How did they affect the rest of the universe? These are questions astronomers and astrophysicists have long pondered.

Now, after 12 years of experimental effort, a team of scientists, led by ASU School of Earth and Space Exploration astronomer Judd Bowman, has detected the fingerprints of the earliest stars in the universe. Using radio signals, the detection provides the first evidence for the oldest ancestors in our cosmic family tree, born by a mere 180 million years after the universe began.

"There was a great technical challenge to making this detection, as sources of noise can be a thousand times brighter than the signal -- it's like being in the middle of a hurricane and trying to hear the flap of a hummingbird's wing." says Peter Kurczynski, the National Science Foundation program officer who supported this study. "These researchers with a small radio antenna in the desert have seen farther than the most powerful space telescopes, opening a new window on the early universe."

Radio Astronomy

To find these fingerprints, Bowman's team used a ground-based instrument called a radio spectrometer, located at the Australia's national science agency (CSIRO) Murchison Radio-astronomy Observatory (MRO) in Western Australia. Through their Experiment to Detect the Global EoR Signature (EDGES), the team measured the average radio spectrum of all the astronomical signals received across most of the southern-hemisphere sky and looked for small changes in power as a function of wavelength (or frequency).

In each instrument, radio waves are collected by an antenna consisting of two rectangular metal panels mounted horizontally on fiberglass legs above a metal mesh. The EDGES detection required the radio quietness at the Murchison Radio-astronomy Observatory, as Australian national legislation limits the use of radio transmitters near the site. This discovery sets the stage for follow-up observations with other powerful low-frequency facilities, including HERA and the forthcoming SKA-low [Credit: CSIRO Australia]

As radio waves enter the ground-based antenna, they are amplified by a receiver, and then digitized and recorded by computer, similar to how FM radio receivers and TV receivers work. The difference is that the instrument is very precisely calibrated and designed to perform as uniformly as possible across many radio wavelengths.

The signals detected by the radio spectrometer in this study came from primordial hydrogen gas that filled the young universe and existed between all the stars and galaxies. These signals hold a wealth of information that opens a new window on how early stars -- and later, black holes, and galaxies -- formed and evolved.

"It is unlikely that we'll be able to see any earlier into the history of stars in our lifetimes," says Bowman. "This project shows that a promising new technique can work and has paved the way for decades of new astrophysical discoveries."

This detection highlights the exceptional radio quietness of the MRO, particularly as the feature found by EDGES overlaps the frequency range used by FM radio stations. Australian national legislation limits the use of radio transmitters within 161.5 miles (260 km) of the site, substantially reducing interference which could otherwise drown out sensitive astronomy observations.

The results of this study have been recently published in Nature by Bowman, with co-authors Alan Rogers of the Massachusetts Institute of Technology's Haystack Observatory, Raul Monsalve of the University of Colorado, and Thomas Mozdzen and Nivedita Mahesh also of ASU's School of Earth and Space Exploration.

Unexpected results

The results of this experiment confirm the general theoretical expectations of when the first stars formed and the most basic properties of early stars.

A timeline of the universe, updated to show when the first stars emerged. This updated timeline of the universe reflects the recent discovery that the first stars emerged by 180 million years after the Big Bang. The research behind this timeline was conducted by Judd Bowman of Arizona State University and his colleagues, with funding from  the National Science Foundation [Credit: N.R.Fuller, National Science Foundation]

"What's happening in this period," says co-author Rogers of MIT's Haystack Observatory, "is that some of the radiation from the very first stars is starting to allow hydrogen to be seen. It's causing hydrogen to start absorbing the background radiation, so you start seeing it in silhouette, at particular radio frequencies. This is the first real signal that stars are starting to form, and starting to affect the medium around them."

The team originally tuned their instrument to look later in cosmic time, but in 2015 decided to extend their search. "As soon as we switched our system to this lower range, we started seeing things that we felt might be a real signature," Rogers says. "We see this dip most strongly at about 78 megahertz, and that frequency corresponds to roughly 180 million years after the Big Bang," Rogers says. "In terms of a direct detection of a signal from the hydrogen gas itself, this has got to be the earliest."

The study also revealed that gas in the universe was probably much colder than expected (less than half the expected temperature). This suggests that either astrophysicists' theoretical efforts have overlooked something significant or that this may be the first evidence of non-standard physics: Specifically, that baryons (normal matter) may have interacted with dark matter and slowly lost energy to dark matter in the early universe, a concept that was originally proposed by Rennan Barkana of Tel Aviv University.

"If Barkana's idea is confirmed," says Bowman, "then we've learned something new and fundamental about the mysterious dark matter that makes up 85 percent of the matter in the universe, providing the first glimpse of physics beyond the standard model."


The next steps in this line of research are for another instrument to confirm this team's detection and to keep improving the performance of the instruments, so that more can be learned about the properties of early stars. "We worked very hard over the last two years to validate the detection," says Bowman, "but having another group confirm it independently is a critical part of the scientific process."

Bowman would also like to see an acceleration of efforts to bring on new radio telescopes like the Hydrogen Epoch of Reionization Array (HERA) and the Owens Valley Long Wavelength Array (OVRO-LWA).

"Now that we know this signal exists," says Bowman, "we need to rapidly bring online new radio telescopes that will be able to mine the signal much more deeply."

The antennas and portions of the receiver used in this experiment were designed and constructed by Rogers and the MIT Haystack Observatory team. The ASU team and Monsalve added the automated antenna reflection measurement system to the receiver, outfitted the control hut with the electronics, constructed the ground plane and conducted the field work for the project. The current version of EDGES is the result of years of design iteration and ongoing detailed technical refinement of the calibration instrumentation to reach the levels of precision necessary for successfully achieving this difficult measurement.

Source: Arizona State University [February 28, 2018]

An international team of astronomers led by the Max Planck Institute for Astronomy (MPIA) has made a surprising discovery about the birthplace of groups of stars located in the halo of our Milky Way galaxy.

The Milky Way galaxy, perturbed by the tidal interaction with a dwarf galaxy, as predicted by N-body simulations.  The locations of the observed stars above and below the disc, which are used to test the perturbation scenario,  are indicated [Credit: T.Mueller/NASA/JPL-Caltech]

These halo stars are grouped together in giant structures that orbit the center of our galaxy, above and below the flat disk of the Milky Way. Researchers thought they may have formed from debris left behind by smaller galaxies that invaded the Milky Way in the past.

But in a study published today in the journal Nature, astronomers now have compelling evidence showing that some of these halo structures actually originate from the Milky Way's disk itself, but were kicked out.

"This phenomenon is called galactic eviction," said co-author Judy Cohen, Kate Van Nuys Page Professor of Astronomy at Caltech. "These structures are pushed off the plane of the Milky Way when a massive dwarf galaxy passes through the galactic disk. This passage causes oscillations, or waves, that eject stars from the disk, either above or below it depending on the direction that the perturbing mass is moving."

"The oscillations can be compared to sound waves in a musical instrument," said lead author Maria Bergemann of MPIA. "We call this 'ringing' in the Milky Way galaxy 'galactoseismology,' which has been predicted theoretically decades ago. We now have the clearest evidence for these oscillations in our galaxy's disk obtained so far!"

For the first time, Bergemann's team presented detailed chemical abundance patterns of these halo stars using the W. M. Keck Observatory on Maunakea, Hawaii."

The analysis of chemical abundances is a very powerful test, which allows, in a way similar to the DNA matching, to identify the parent population of the star. Different parent populations, such as the Milky Way disk or halo, dwarf satellite galaxies or globular clusters, are known to have radically different chemical compositions. So once we know what the stars are made of, we can immediately link them to their parent populations," said Bergemann.


The scientists investigated 14 stars located in two different halo structures -- the Triangulum-Andromeda (Tri-And) and the A13 stellar overdensities. These two structures lie on opposite sides of the Milky Way disk; about 14,000 light years above and below the Galactic plane.

The team obtained spectra of the halo stars using Keck Observatory's High-Resolution Echelle Spectrometer (HIRES).

"The high throughput and high spectral resolution of HIRES were crucial to the success of the observations of the stars in the outer part of the Milky Way," said Cohen. "Another key factor was the smooth operation of Keck Observatory; good pointing and smooth operation allows one to get spectra of more stars in only a few nights of observation. The spectra in this study were obtained in only one night of Keck time, which shows how valuable even a single night can be."

The team also obtained a spectrum of one additional star taken with the European Southern Observatory's Very Large Telescope (VLT) in Chile.

When comparing the chemical compositions of these stars with the ones found in other cosmic structures, the scientists were surprised to find that the chemical compositions are almost identical, both within and between these groups, and closely match the abundance patterns of the Milky Way outer disk stars.

This provides compelling evidence that the halo stars most likely originate from the Galactic thin disk (the younger part of Milky Way, strongly concentrated towards the Galactic plane) itself.

These findings are very exciting because they indicate the Milky Way's disk and its dynamics are significantly more complex than previously thought.

"We showed that it may be fairly common for groups of stars in the disk to be relocated to more distant realms within the Milky Way -- having been 'kicked out' by an invading satellite galaxy. Similar chemical patterns may also be found in other galaxies, indicating a potential galactic universality of this dynamic process," said co-author Allyson Sheffield of LaGuardia Community College/CUNY.

As a next step, the astronomers plan to analyse the spectra of additional stars in the Tri-And and A13 overdensities, as well as stars in other stellar structures further away from the disk. They also plan to determine masses and ages of these stars so they can constrain the time limits of when this galactic eviction took place.

Source: W. M. Keck Observatory [February 26, 2018]

But why would naked singularities exist in 5-D and in 4-D when you change the geometry, but never in a flat 4-D universe like ours? “It’s like, what the heck!” Santos said. “It’s so weird you should work on it, right? There has to be something here.”

Astronomers have the "all-clear" for an exciting test of Einstein's Theory of General Relativity, thanks to a new discovery about S0-2's star status.

The orbit of S0-2 (light blue) located near the Milky Way's supermassive black hole will be used to test Einstein's Theory of General Relativity and generate potentially new gravitational models [Credit: W. M. Keck Observatory]

Up until now, it was thought that S0-2 may be a binary, a system where two stars circle around each other. Having such a partner would have complicated the upcoming gravity test.

But in a study published recently in The Astrophysical Journal, a team of astronomers led by a UCLA scientist from Hawaii has found that S0-2 does not have a significant other after all, or at least one that is massive enough to get in the way of critical measurements that astronomers need to test Einstein's theory.

The researchers made their discovery by obtaining spectroscopic measurements of S0-2 using W. M. Keck Observatory's OH-Suppressing Infrared Imaging Spectrograph (OSIRIS) and Laser Guide Star Adaptive Optics.

"This is the first study to investigate S0-2 as a spectroscopic binary," said lead author Devin Chu of Hilo, an astronomy graduate student with UCLA's Galactic Center Group. "It's incredibly rewarding. This study gives us confidence that a S0-2 binary system will not significantly affect our ability to measure gravitational redshift."

Einstein's Theory of General Relativity predicts that light coming from a strong gravitational field gets stretched out, or "redshifted." Researchers expect to directly measure this phenomenon beginning in the spring as S0-2 makes its closest approach to the supermassive black hole at the center of our Milky Way galaxy.

This will allow the Galactic Center Group to witness the star being pulled at maximum gravitational strength - a point where any deviation to Einstein's theory is expected to be the greatest.

"It will be the first measurement of its kind," said co-author Tuan Do, deputy director of the Galactic Center Group. "Gravity is the least well-tested of the forces of nature. Einstein's theory has passed all other tests with flying colors so far, so if there are deviations measured, it would certainly raise lots of questions about the nature of gravity!"

"We have been waiting 16 years for this," said Chu. "We are anxious to see how the star will behave under the black hole's violent pull. Will S0-2 follow Einstein's theory or will the star defy our current laws of physics? We will soon find out!"

The study also sheds more light on the strange birth of S0-2 and its stellar neighbors in the S-Star Cluster. The fact that these stars exist so close to the supermassive black hole is unusual because they are so young; how they could've formed in such a hostile environment is a mystery.

"Star formation at the Galactic Center is difficult because the brute strength of tidal forces from the black hole can tear gas clouds apart before they can collapse and form stars," said Do.

"S0-2 is a very special and puzzling star," said Chu. "We don't typically see young, hot stars like S0-2 form so close to a supermassive black hole. This means that S0-2 must have formed a different way."

There are several theories that provide a possible explanation, with S0-2 being a binary as one of them. "We were able to put an upper limit on the mass of a companion star for S0-2," said Chu. This new constraint brings astronomers closer to understanding this unusual object.

"Stars as massive as S0-2 almost always have a binary companion. We are lucky that having no companion makes the measurements of general relativistic effects easier, but it also deepens the mystery of this star," said Do.

The Galactic Center Group now plans to study other S-Stars orbiting the supermassive black hole, in hopes of differentiating between the varying theories that attempt to explain why S0-2 is single.

Source: W. M. Keck Observatory [February 22, 2018]