Month: October 2018

Kin Of Gravitational Wave Source Discovered

On October 16, 2017, an international group of astronomers and physicists excitedly reported the first simultaneous detection of light and gravitational waves from the same source — a merger of two neutron stars. Now, a team that includes several University of Maryland astronomers has identified a direct relative of that historic event.

The newly described object, named GRB150101B, was reported as a gamma-ray burst localized by NASA’s Neil Gehrels Swift Observatory in 2015. Follow-up observations by NASA’s Chandra X-ray Observatory, the Hubble Space Telescope (HST) and the Discovery Channel Telescope (DCT) suggest that GRB150101B shares remarkable similarities with the neutron star merger, named GW170817, discovered by the Laser Interferometer Gravitational-wave Observatory (LIGO) and observed by multiple light-gathering telescopes in 2017.

A new study suggests that these two separate objects may, in fact, be directly related. The results were published on October 16, 2018 in the journal Nature Communications.

“It’s a big step to go from one detected object to two,” said study lead author Eleonora Troja, an associate research scientist in the UMD Department of Astronomy with a joint appointment at NASA’s Goddard Space Flight Center. “Our discovery tells us that events like GW170817 and GRB150101B could represent a whole new class of erupting objects that turn on and off — and might actually be relatively common.”

Troja and her colleagues suspect that both GRB150101B and GW170817 were produced by the same type of event: a merger of two neutron stars. These catastrophic coalescences each generated a narrow jet, or beam, of high-energy particles. The jets each produced a short, intense gamma-ray burst (GRB) — a powerful flash that lasts only a few seconds. GW170817 also created ripples in space-time called gravitational waves, suggesting that this might be a common feature of neutron star mergers.

The apparent match between GRB150101B and GW170817 is striking: both produced an unusually faint and short-lived gamma ray burst and both were a source of bright, blue optical light and long-lasting X-ray emission. The host galaxies are also remarkably similar, based on HST and DCT observations. Both are bright elliptical galaxies with a population of stars a few billion years old that display no evidence of new star formation.

“We have a case of cosmic look-alikes,” said study co-author Geoffrey Ryan, a postdoctoral researcher in the UMD Department of Astronomy and a fellow of the Joint Space-Science Institute. “They look the same, act the same and come from similar neighborhoods, so the simplest explanation is that they are from the same family of objects.”

In the cases of both GRB150101B and GW170817, the explosion was likely viewed “off-axis,” that is, with the jet not pointing directly towards Earth. So far, these events are the only two off-axis short GRBs that astronomers have identified.

The optical emission from GRB150101B is largely in the blue portion of the spectrum, providing an important clue that this event is another kilonova, as seen in GW170817. A kilonova is a luminous flash of radioactive light that produces large quantities of important elements like silver, gold, platinum and uranium.

While there are many commonalities between GRB150101B and GW170817, there are two very important differences. One is their location: GW170817 is relatively close, at about 130 million light years from Earth, while GRB150101B lies about 1.7 billion light years away.

The second important difference is that, unlike GW170817, gravitational wave data does not exist for GRB150101B. Without this information, the team cannot calculate the masses of the two objects that merged. It is possible that the event resulted from the merger of a black hole and a neutron star, rather than two neutron stars.

“Surely it’s only a matter of time before another event like GW170817 will provide both gravitational wave data and electromagnetic imagery. If the next such observation reveals a merger between a neutron star and a black hole, that would be truly groundbreaking,” said study co-author Alexander Kutyrev, an associate research scientist in the UMD Department of Astronomy with a joint appointment at NASA’s Goddard Space Flight Center. “Our latest observations give us renewed hope that we’ll see such an event before too long.”

It is possible that a few mergers like the ones seen in GW170817 and GRB150101B have been detected previously, but were not properly identified using complementary observations in different wavelengths of light, according to the researchers. Without such detections — in particular, at longer wavelengths such as X-rays or optical light — it is very difficult to determine the precise location of events that produce gamma-ray bursts.

In the case of GRB150101B, astronomers first thought that the event might coincide with an X-ray source detected by Swift in the center of the galaxy. The most likely explanation for such a source would be a supermassive black hole devouring gas and dust. However, follow-up observations with Chandra placed the event further away from the center of the host galaxy.

According to the researchers, even if LIGO had been operational in early 2015, it would very likely not have detected gravitational waves from GRB150101B because of the event’s greater distance from Earth. All the same, every new event observed with both LIGO and multiple light-gathering telescopes will add important new pieces to the puzzle.

“Every new observation helps us learn better how to identify kilonovae with spectral fingerprints: silver creates a blue color, whereas gold and platinum add a shade of red, for example,” Troja added. “We’ve been able identify this kilonova without gravitational wave data, so maybe in the future, we’ll even be able to do this without directly observing a gamma-ray burst.”

Astronomers Find A Cosmic Titan In The Early Universe

An international team of astronomers has discovered a titanic structure in the early Universe, just two billion years after the Big Bang. This galaxy proto-supercluster, nicknamed Hyperion, is the largest and most massive structure yet found at such a remote time and distance.

The team that made the discovery was led by Olga Cucciati of Istituto Nazionale di Astrofisica (INAF) Bologna, Italy and project scientist Brian Lemaux in the Department of Physics, College of Letters and Science at the University of California, Davis, and included Lori Lubin, professor of physics at UC Davis. They used the VIMOSinstrument on ESO’s Very Large Telescope in Paranal, Chile to identify a gigantic proto-supercluster of galaxies forming in the early Universe, just 2.3 billion years after the Big Bang.

Hyperion is the largest and most massive structure to be found so early in the formation of the Universe, with a calculated mass more than one million billion times that of the Sun. This enormous mass is similar to that of the largest structures observed in the Universe today, but finding such a massive object in the early Universe surprised astronomers.

“This is the first time that such a large structure has been identified at such a high redshift, just over 2 billion years after the Big Bang,” Cucciati said. “Normally these kinds of structures are known at lower redshifts, which means when the Universe has had much more time to evolve and construct such huge things. It was a surprise to see something this evolved when the Universe was relatively young.”

Supercluster mapped in three dimensions

Located in the constellation of Sextans (The Sextant), Hyperion was identified by a novel technique developed at UC Davis to analyze the vast amount of data obtained from the VIMOS Ultra-Deep Survey led by Olivier Le Fèvre from Laboratoire d’Astrophysique de Marseille, Centre National de la Recherche Scientifique and Centre National d’Etudes Spatiales. The VIMOS instrument can measure the distance to hundreds of galaxies at the same time, making it possible to map the position of galaxies within the forming supercluster in three dimensions.

The team found that Hyperion has a very complex structure, containing at least seven high-density regions connected by filaments of galaxies, and its size is comparable to superclusters closer to Earth, though it has a very different structure.

“Superclusters closer to Earth tend to a much more concentrated distribution of mass with clear structural features,” Lemaux said. “But in Hyperion, the mass is distributed much more uniformly in a series of connected blobs, populated by loose associations of galaxies.”

The researchers are comparing the Hyperion findings with results from the Observations of Redshift Evolution in Large Scale Environments (ORELSE) survey, led by Lubin. The ORELSE survey uses telescopes at the W.M. Keck Observatory in Hawaii to study superclusters closer to Earth. Lubin and Lemaux are also using the Keck observatory to map out Hyperion and similar structures more completely.

The contrast between Hyperion and less distant superclusters is most likely due to the fact that nearby superclusters have had billions of years for gravity to gather matter together into denser regions — a process that has been acting for far less time in the much younger Hyperion.

Given its size so early in the history of the Universe, Hyperion is expected to evolve into something similar to the immense structures in the local Universe such as the superclusters making up the Sloan Great Wall or the Virgo Supercluster that contains our own galaxy, the Milky Way.

“Understanding Hyperion and how it compares to similar recent structures can give insights into how the Universe developed in the past and will evolve into the future, and allows us the opportunity to challenge some models of supercluster formation,” Cucciati said. “Unearthing this cosmic titan helps uncover the history of these large-scale structures.”

Zombie Storm Leslie Slammed Portugal, France And Spain With Unusual Strength

There are no two ways about it — the storm known as Leslie was a weirdo, the strangest to develop in the Atlantic Ocean this year, if not in many years.

The storm finally crashed into Europe’s Iberian Peninsula over the weekend, creating all sorts of havoc, after meandering over the open Atlantic Ocean for 19 days, where it took on many forms.

Previously a hurricane, Leslie arrived in Europe as an intense extratropical or mid-latitude storm, having lost its tropical characteristics. While not a hurricane in name at landfall, it was just as powerful, battering the Iberian Peninsula at virtually unprecedented strength.

Winds gusted to 109 mph along the western coast of Portugal in the community Figueira da Foz. The storm left behind flooding, uprooted hundreds of trees and caused 27 minor injuries in Portugal.

The unusually strong winds were due in part to a sting jet, a potent but narrow surge of exceptional winds caused when evaporative cooling within the storm drags the jet stream to the surface.

Leslie became the first tropically borne system to directly impact Spain since Vince in 2005 and was far more powerful. The BBC said winds gusted over 60 mph in the city of Zamora.

Farther north, devastating floods engulfed France as Leslie’s tropical connection drenched southern areas with heavy rainfall. At least 10 deaths were blamed on the floods.

Meteo-France reported the following rainfall totals in the south of France:11.6 inches (296 mm) fell in eight hours near Carcassonne, 9.6 inches (244 mm) fell in six hours and 4.4 inches (111 mm) in two hours.
14.3 inches (364 mm) fell in 24 hours in the Haut-Languedoc region. As of Tuesday, Leslie’s remnant circulation had merged with the remnants of Hurricane Michael, both entities substantially weakened.

Leslie first got its name on Sept. 23 as a subtropical storm in the middle of nowhere in the open Atlantic. Spinning absentmindedly in the central North Atlantic, the prospects for Leslie’s development weren’t good. In its first advisory, the National Hurricane Center ironically said it was “forecast to be a short-lived cyclone.”

Nobody knew Leslie would become the 11th-longest-lived Atlantic cyclone on record, fluctuating between tropical storm and Category 1 strength for at least 19 days.

But Leslie defied the odds, stubbornly dodging systems that could harvest its energy and strengthening when all signs suggested it shouldn’t. The National Hurricane Center first stated that Leslie was “forecast to become absorbed by a larger non-tropical low” within two or three days.

On Sept. 25, Leslie fell apart into a subtropical depression right on schedule. All done. Or so we thought.

Leslie’s brief falter didn’t last long, and the capricious storm rose from the dead two days later. The “zombie cyclone” took on the characteristics of a mid-latitude nor’easter-type storm instead, stirring up the seas with powerful hurricane-force winds on Sept. 27. Meteorologists refer to this type of storm as extratropical. Despite gusts exceeding the 74 mph criterion, however, Leslie’s cold-core nature did not fit the bill for it to be classified as a hurricane.

That’s when Leslie decided to switch things up. The post-tropical cyclone swirled in some warmer air on the 28th and became subtropical — a wacky hybrid combination of a tropical cyclone and a mid-latitude low — again.

Until this point, Leslie was never “officially” a tropical cyclone or hurricane. Only at 11 p.m. Atlantic time on Sept. 29 did the hurricane center finally award a tropical designation to Leslie. By then, the 50 mph storm was quickly acquiring the textbook hurricane shape and at last matured into a Category 1 hurricane with 80 mph winds on Oct. 3.

All the while, Leslie didn’t bother anybody but mariners. The storm went through an entire cycle again between different structures, wandering over the open ocean. Leslie began to peter out around Oct. 7 but then got feisty on the 8th. By Oct. 10, Leslie was mean — baring its teeth with winds of 90 mph tightly packed around a symmetric clouded-in center.

Part of Leslie’s perceived longevity is due to the wide arsenal of satellite imagery currently at the disposal of Hurricane Center meteorologists. Nowadays, forecasters can utilize remote sensing to better understand the internal organization of storms. A mere three or four decades ago, these tools existed in a much more rudimentary form — and Leslie probably would not have been named until it actually looked like a tropical cyclone in early October.

The takeaway? Leslie’s life span is certainly unusually long, but by no means unheard of. The San Ciriaco hurricane of 1899 persisted a whopping 27 days, and in the Pacific, cyclones have stuck around even longer. John clocked in at a staggering 30 days in 1994.

New Maps To Support Decision-Making After An Earthquake

Researchers from diverse institutions, including the School of Land Surveying, Geodesy and Mapping Engineering from Universidad Politécnica de Madrid, have developed a new methodology to create easy-to-understand maps for decision-making support after large earthquakes.

By using spatial geodesic techniques, such as the Global Navigation Satellite System (GNSS) and the Interferometric synthetic aperture radar, (InSAR), researchers have developed a methodology to estimate the activation of faults and volcanoes in a region after an earthquake. The results are presented in a traffic light scale in order to improve the transfer of the obtained scientific results after an earthquake to the management of this post-event.

This study has been led by researchers from Universidad Politécnica de Madrid (UPM), Complutense (UCM) and the Geological and Mining Institute of Spain (IGME) and published in the journal Remote Sensing.

The developed methodology was applied to the earthquake that occurred in April 2016 in Pedernales (Mw 7.8), and is based on the estimation of effort changes in nearby faults and volcanoes which are the consequences of the energy release after an earthquake. To do this, researchers combined, modeled and assessed geological data from catalogs of faults and volcanoes in the area; they also assessed data from the cosmic deformation caused by an earthquake and obtained with techniques of spatial geodesics: InSAR- Interferometric Synthetic Aperture Radar and Global Navigation Satellite System, GNSS.

From the results of this analysis, researchers developed a set of simplified maps represented with a traffic light scale to find out if an earthquake will be activated after a volcano. To quantify this estimation is a challenge to be developed in future research.

Although the techniques used for the analysis and modeling of data are widely used in the scientific field, the novelty of this study lies in the transfer of these results to the post-event management field. This methodology could also be adapted to pre-event management.

Huge Earthquake Simulator To Get An Upgrade

The University of California, San Diego’s outdoor shake table in Scripps Ranch will soon give engineers a truer sense of the fury released when big earthquakes erupt in places around the world.

The National Science Foundation gave the school $16.3 million to upgrade the center so it can more accurately simulate quakes, a complex phenomenon that in some years kills hundreds of thousands of people worldwide.

The table is the largest of its kind and has conducted experiments that have led to tougher building and design codes for bridges and housing. But it can move structures only backward and forward. Quakes can move the ground in many directions.

Engineers will modify the table so that it also can move up and down, right and left, and simulate the pitch, roll and yaw that can come with ground motion. Collectively, these movements are called the “six degrees of freedom.”

The upgrade involves adding pistons and power to a table that’s used by researchers from around nation to simulate quakes big enough to send seismic waves coursing through the earth for weeks.

“We will be able to reproduce earthquake motions with the most accuracy of any shake table in the world,” said Joel Conte, the structural engineer who is overseeing the project. “This will accelerate the discovery of the knowledge engineers need to build new bridges, power plants, dams, levees, telecommunication towers, wind turbines, retaining walls, tunnels, and to retrofit older structures. It will enhance the resiliency of our communities.”

The upgrade comes at a worrisome time in California.

In June, the U.S. Geological Survey said 38 high-rise buildings in San Francisco constructed between 1964 and 1994 could buckle if they were hit by the type of earthquake that devastated the city in 1906. The list includes the Transamerica Pyramid in the Financial District.

There’s also concern about a newer skyscraper, the 58-story Millennium Tower, which has been sinking and tilting, making it more vulnerable to big quakes.

San Diego is also on shaky ground.

In 2017, the Earthquake Engineering Research Institute released a report that says that 2,000 people could die in San Diego if a 6.9 magnitude quake erupts on the Rose Canyon fault, which runs through the heart of the city. Potential property damage: $40 billion.

The EERI emphasized that the figures are just estimates because modeling the complexities of earthquakes is hard to do with existing models and technology.

Even so, engineers have made progress.

Since it opened in the late 1980s, UC San Diego’s Powell Laboratories has been heavily involved in developing and testing key portions of roads and bridges, leading to changes in building codes.

The shake table was added in 2004 to give scientists and engineers better ability to test large structures, from wood-frame buildings to bridge columns to a 70-foot wind turbine.

The need for such a table had been apparent for decades.

The 6.7 magnitude Northridge quake in 1994 appears to have caused the ground to move vertically and horizontally. That vertical movement may be the reason that some bridge support columns rose and pierced the decks of bridges.

Such wild ground motion wasn’t unknown to engineers. The 1971 San Fernando earthquake, which measured 6.6, appears to have caused the soil to rotate in some areas. That, in turn, may have caused some buildings to turn like corkscrews.

The movement contributed to the billions of dollars in property damage inflicted by the quake.

The table has been used to simulate some of those jarring events, notably the Northridge quake.

That earthquake caused the collapse of a parking garage at Cal State Northridge. Engineers from the University of Arizona built a similar garage in 2008, and then shook it harder than the real quake.

The experiment revealed a great deal about how such structures absorb and distribute energy, leading to a strengthening of national building codes.

More recently, a team led by UC San Diego built and tested a five-story building that had many of the features of a hospital—such as an ICU and a surgery suite—and a working elevator and a sprinkler system. The goal was to understand what would happen inside a hospital during a catastrophic quake.

To ensure that they didn’t miss anything, engineers placed 500 sensors in and around the building, and installed 70 cameras.

Then they simulated several high-intensity earthquakes, and later set part of the building on fire to replicate a frequent aftereffect of quakes.

“What we are doing is the equivalent of giving a building an EKG,” lead engineer Tara Hutchinson said.

The experiment helped lead to the design of safer hospitals, and it was followed by a project that focused on a subject of great concern in California—four-story wood-frame residential buildings that have garages on the first floor.

The structures -built mostly in the 1920s, ’30s and ’40s—are now considered vulnerable to collapse in a huge quake.

In 2013, Colorado State University built one of the structures on the shake table and outfitted it with various types of retrofitting to see what would happen.

The result was good, and bad.

The building survived shake tests with the retrofitting in place. When it was taken out, calamity ensued.

“There was creaking and crunching, then a thunderous collapse, followed by dust and debris floating up,” said John W. van de Lindt, the Colorado State engineer who led the project.

Now, Lindt is drawing up plans for a 10-story building that will be built on the same spot. But this time, he’ll be able to move the building in any direction he wants.

“The U.S. and California have really been at the forefront of this kind of research,” Lindt said. “The upgrade will help us keep pace with the world. We really need this.”

Giant Planets Around Young Star Raise Questions About How Planets Form

Researchers have identified a young star with four Jupiter and Saturn-sized planets in orbit around it, the first time that so many massive planets have been detected in such a young system. The system has also set a new record for the most extreme range of orbits yet observed: the outermost planet is more than a thousand times further from the star than the innermost one, which raises interesting questions about how such a system might have formed.

The star is just two million years old — a ‘toddler’ in astronomical terms — and is surrounded by a huge disc of dust and ice. This disc, known as a protoplanetary disc, is where the planets, moons, asteroids and other astronomical objects in stellar systems form.

The star was already known to be remarkable because it contains the first so-called hot Jupiter — a massive planet orbiting very close to its parent star — to have been discovered around such a young star. Although hot Jupiters were the first type of exoplanet to be discovered, their existence has long puzzled astronomers because they are often thought to be too close to their parent stars to have formed in situ.

Now, a team of researchers led by the University of Cambridge have used the Atacama Large Millimeter/submillimeter Array (ALMA) to search for planetary ‘siblings’ to this infant hot Jupiter. Their image revealed three distinct gaps in the disc, which, according to their theoretical modelling, were most likely caused by three additional gas giant planets also orbiting the young star. Their results are reported in The Astrophysical Journal Letters.

The star, CI Tau, is located about 500 light years away in a highly-productive stellar ‘nursery’ region of the galaxy. Its four planets differ greatly in their orbits: the closest (the hot Jupiter) is within the equivalent of the orbit of Mercury, while the farthest orbits at a distance more than three times greater than that of Neptune. The two outer planets are about the mass of Saturn, while the two inner planets are respectively around one and 10 times the mass of Jupiter.

The discovery raises many questions for astronomers. Around 1% of stars host hot Jupiters, but most of the known hot Jupiters are hundreds of times older than CI Tau. “It is currently impossible to say whether the extreme planetary architecture seen in CI Tau is common in hot Jupiter systems because the way that these sibling planets were detected — through their effect on the protoplanetary disc — would not work in older systems which no longer have a protoplanetary disc,” said Professor Cathie Clarke from Cambridge’s Institute of Astronomy, the study’s first author.

According to the researchers, it is also unclear whether the sibling planets played a role in driving the innermost planet into its ultra-close orbit, and whether this is a mechanism that works in making hot Jupiters in general. And a further mystery is how the outer two planets formed at all.

“Planet formation models tend to focus on being able to make the types of planets that have been observed already, so new discoveries don’t necessarily fit the models,” said Clarke. “Saturn mass planets are supposed to form by first accumulating a solid core and then pulling in a layer of gas on top, but these processes are supposed to be very slow at large distances from the star. Most models will struggle to make planets of this mass at this distance.”

The task ahead will be to study this puzzling system at multiple wavelengths to get more clues about the properties of the disc and its planets. In the meantime, ALMA — the first telescope with the capability of imaging planets in the making — will likely throw out further surprises in other systems, re-shaping our picture of how planetary systems form.

The research has been supported by the European Research Council.

Mystery At The Center Of The Milky Way Solved

Astronomers from Lund University in Sweden have now found the explanation to a recent mystery at the center of the Milky Way galaxy: the high levels of scandium discovered last spring near the galaxy’s giant black hole were in fact an optical illusion.

Last spring, researchers published a study about the apparent presence of astonishing and dramatically high levels of three different elements in red giant stars, located less than three light years away from the big black hole at the centre of our galaxy. Various possible explanations were presented, for example that the high levels were a result of earlier stars being disrupted as they fall into the black hole, or a result of debris from the collisions of neutron stars.

Now another group of astronomers from Lund University among others, in collaboration with UCLA in California, have found an explanation for the high levels of scandium, vanadium and yttrium. They argue that the so-called spectral lines presented last spring were actually an optical illusion. Spectral lines are used to find out which elements a star contains — by using its own light.

“These giant red stars have used up most of their hydrogen fuel and their temperatures are therefore only half of the sun’s,” says Brian Thorsbro, lead author of the study and doctoral student in astronomy at Lund University.

According to the new study, the lower temperatures of the giant stars helped to create the optical illusion that appeared in the measurements of spectral lines. Specifically, it means that the electrons in the elements behave differently at different temperatures, which in turn can be misleading when measuring the spectral lines of elements in different stars. The conclusion is the result of a close collaboration between astronomers and atomic physicists.

Brian Thorsbro and his colleagues have had the world’s largest telescope, at the W. M. Keck Observatory on Mauna Kea, Hawaii, at their disposal, thanks to their collaboration with R. Michael Rich at UCLA. Using this telescope and others, the research team is currently conducting a comprehensive mapping of the central areas of the Milky Way, exploring the spectral lines in the light from different stars to find out which elements they contain. The purpose is to gain an understanding of the events that have occurred in the history of the Milky Way, but also to understand how galaxies in general have formed.

“Our research collaboration is world-leading in terms of systematically mapping the elements contained in the huge central star cluster — the star cluster that surrounds the black hole,” says research leader and astronomer Nils Ryde at Lund University.

The spectral lines for different elements are recorded in a high-resolution spectrometer — an advanced camera that generates a rainbow of the starlight. The research team has studied the part of the spectrum consisting of near-infrared light, i.e. the heat radiation emitted by the stars. The reason for this is that infrared light can penetrate the dust that obstructs the line-of-sight between us and the centre of the Milky Way, approximately 25,000 light years away. The technology for recording this light is very advanced, and has only recently become available to astronomers.

“We have only started to map the stellar compositions in these central areas of the Milky Way,” says Nils Ryde.