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Solving the dark energy mystery: A new sky survey assignment for a 45-year-old telescope

SMU and other members of a scientific consortium prepare for installation of the Dark Energy Spectroscopic Instrument to survey the night sky from a mile-high mountain peak in Arizona

As part of a large scientific consortium studying dark energy, SMU physicists are on course to help create the largest 3-D map of the universe ever made.

The map will emerge from data gathered by the Dark Energy Spectroscopic Instrument (DESI) being installed on the Nicholas U. Mayall Telescope atop a mountain in Arizona.

The map could help solve the mystery of dark energy, which is driving the accelerating expansion of the universe.

DESI will capture about 10 times more data than a predecessor survey of space using an array of 5,000 swiveling robots. Each robot will be carefully choreographed to point a fiber-optic cable at a preprogrammed sequence of deep-space objects, including millions of galaxies and quasars, which are galaxies that harbor massive, actively feeding black holes.

“DESI will provide the first precise measures of the expansion history of the universe covering approximately the last 10 billion years,” said SMU physicist Robert Kehoe, a professor in the SMU Department of Physics. “This is most of the 13 billion year age of the universe, and it encompasses a critical period in which the universe went from being matter-dominated to dark-energy dominated.”

The universe was expanding, but at a slowing pace, until a few billion years ago, Kehoe said.

“Then the expansion started accelerating,” he said. “The unknown ‘dark energy’ driving that acceleration is now dominating the universe. Seeing this transition clearly will provide a critical test of ideas of what this dark energy is, and how it may tie into theories of gravitation and other fundamental forces.”

The Mayall telescope was originally commissioned 45 years ago to survey the night sky and record observations on glass photographic plates. The telescope is tucked inside a 14-story, 500-ton dome atop a mile-high peak at the National Science Foundation’s Kitt Peak National Observatory – part of the National Optical Astronomy Observatory.

SMU researchers have conducted observing with the Mayall. Decommissioning of that telescope allows for building DESI in it’s place, as well as reusing some parts of the telescope and adding major new sytems. As part of DESI, SMU is involved in development of software for operation of the experiment, as well as for data simulation to aid data anlysis.

“We are also involved in studying the ways in which observational effects impact the cosmology measurements DESI is pursuing,” Kehoe said. SMU graduate students Govinda Dhungana and Ryan Staten also work on DESI. A new addition to the SMU DESI team, post-doctoral researcher Sarah Eftekharzadeh, is working on the SMU software and has studied the same kinds of galaxies
DESI will be measuring.

Now the dome is closing on the previous science chapters of the 4-meter Mayall Telescope so that it can prepare for its new role in creating the 3-D map.

The temporary closure sets in motion the largest overhaul in the telescope’s history and sets the stage for the installation of the Dark Energy Spectroscopic Instrument, which will begin a five-year observing run next year.

“This day marks an enormous milestone for us,” said DESI Director Michael Levi of the Department of Energy’s Lawrence Berkeley National Laboratory , which leads the project’s international collaboration. “Now we remove the old equipment and start the yearlong process of putting the new stuff on.”

More than 465 researchers from about 71 institutions are participating in the DESI collaboration.

The entire top end of the telescope, which weighs as much as a school bus and houses the telescope’s secondary mirror and a large digital camera, will be removed and replaced with DESI instruments. A large crane will lift the telescope’s top end through the observing slit in its dome.

Besides providing new insights about the universe’s expansion and large-scale structure, DESI will also help to set limits on theories related to gravity and the formative stages of the universe, and could even provide new mass measurements for a variety of elusive yet abundant subatomic particles called neutrinos.

“One of the primary ways that we learn about the unseen universe is by its subtle effects on the clustering of galaxies,” said DESI collaboration co-spokesperson Daniel Eisenstein of Harvard University. “The new maps from DESI will provide an exquisite new level of sensitivity in our study of cosmology.”

Mayall’s sturdy construction is perfect platform for new 9-ton instrument
The Mayall Telescope has played an important role in many astronomical discoveries, including measurements supporting the discovery of dark energy and establishing the role of dark matter in the universe from measurements of galaxy rotation. Its observations have also been used in determining the scale and structure of the universe. Dark matter and dark energy together are believed to make up about 95 percent of all of the universe’s mass and energy.

It was one of the world’s largest optical telescopes at the time it was built, and because of its sturdy construction it is perfectly suited to carry the new 9-ton instrument.

“We started this project by surveying large telescopes to find one that had a suitable mirror and wouldn’t collapse under the weight of such a massive instrument,” said Berkeley Lab’s David Schlegel, a DESI project scientist.

Arjun Dey, the NOAO project scientist for DESI, explained, “The Mayall was precociously engineered like a battleship and designed with a wide field of view.”

The expansion of the telescope’s field-of-view will allow DESI to map out about one-third of the sky.

DESI will transform the speed of science with automated preprogrammed robots
Brenna Flaugher, a DESI project scientist who leads the astrophysics department at Fermi National Accelerator Laboratory, said DESI will transform the speed of science at the Mayall Telescope.

“The telescope was designed to carry a person at the top who aimed and steered it, but with DESI it’s all automated,” she said. “Instead of one at a time we can measure the velocities of 5,000 galaxies at a time – we will measure more than 30 million of them in our five-year survey.”

DESI will use an array of 5,000 swiveling robots, each carefully choreographed to point a fiber-optic cable at a preprogrammed sequence of deep-space objects, including millions of galaxies and quasars, which are galaxies that harbor massive, actively feeding black holes.

The fiber-optic cables will carry the light from these objects to 10 spectrographs, which are tools that will measure the properties of this light and help to pinpoint the objects’ distance and the rate at which they are moving away from us. DESI’s observations will provide a deep look into the early universe, up to about 11 billion years ago.

DESI will capture about 10 times more data than a predecessor survey
The cylindrical, fiber-toting robots, which will be embedded in a rounded metal unit called a focal plate, will reposition to capture a new exposure of the sky roughly every 20 minutes. The focal plane assembly, which is now being assembled at Berkeley Lab, is expected to be completed and delivered to Kitt Peak this year.

DESI will scan one-third of the sky and will capture about 10 times more data than a predecessor survey, the Baryon Oscillation Spectroscopic Survey (BOSS). That project relied on a manually rotated sequence of metal plates – with fibers plugged by hand into pre-drilled holes – to target objects.

All of DESI’s six lenses, each about a meter in diameter, are complete. They will be carefully stacked and aligned in a steel support structure and will ultimately ride with the focal plane atop the telescope.

Each of these lenses took shape from large blocks of glass. They have criss-crossed the globe to receive various treatments, including grinding, polishing, and coatings. It took about 3.5 years to produce each of the lenses, which now reside at University College London in the U.K. and will be shipped to the DESI site this spring.

Precise measurements of millions of galaxies will reveal effects of dark energy
The Mayall Telescope has most recently been enlisted in a DESI-supporting sky survey known as the Mayall z-Band Legacy Survey, which is one of four sky surveys that DESI will use to preselect its targeted sky objects. SMU astrophysicists carried out observing duties on that survey, which wrapped up just days ago on Feb. 11, to support the coming DESI scientific results.

Data from these surveys are analyzed at Berkeley Lab’s National Energy Research Scientific Computing Center, a DOE Office of Science User Facility. Data from these surveys have been released to the public at http://legacysurvey.org.

“We can see about a billion galaxies in the survey images, which is quite a bit of fun to explore,” Schlegel said. “The DESI instrument will precisely measure millions of those galaxies to see the effects of dark energy.”


Levi noted that there is already a lot of computing work underway at the Berkeley computing center to prepare for the stream of data that will pour out of DESI once it starts up.

“This project is all about generating huge quantities of data,” Levi said. “The data will go directly from the telescope to the Berkeley computing center for processing. We will create hundreds of universes in these computers and see which universe best fits our data.”

Installation of DESI’s components is expected to begin soon and to wrap up in April 2019, with first science observations planned in September 2019.

“Installing DESI on the Mayall will put the telescope at the heart of the next decade of discoveries in cosmology,” said Risa Wechsler, DESI collaboration co-spokesperson and associate professor of physics and astrophysics at SLAC National Accelerator Laboratory and Stanford University. “The amazing 3-D map it will measure may solve some of the biggest outstanding questions in cosmology, or surprise us and bring up new ones.” — Berkeley Lab and SMU

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SMU study finds earthquakes continue for years after gas field wastewater injection stops

High rates of injection and large volumes can perturb critically stressed faults, triggering earthquakes years after wastewater wells are shut in.

Efforts to stop human-caused earthquakes by shutting down wastewater injection wells that serve adjacent oil and gas fields may oversimplify the challenge, according to a new study from seismologists at Southern Methodist University, Dallas.

The seismologists analyzed a sequence of earthquakes at DFW Airport and found that even though wastewater injection was halted after a year, the earthquakes continued.

The sequence of quakes began in 2008, and wastewater injection was halted in 2009. But earthquakes continued for at least seven more years.

“This tells us that high-volume injection, even if it’s just for a short time, when it’s near a critically stressed fault, can induce long-lasting seismicity,” said SMU seismologist Paul O. Ogwari, who developed a unique method of data analysis that yielded the study results.

The earthquakes may be continuing even now, said Ogwari, whose analysis extended through 2015.

The study’s findings indicate that shutting down injection wells in reaction to earthquakes, as some states such as Oklahoma and Arkansas are doing, may not have the desired effect of immediately stopping further earthquakes, said seismologist Heather DeShon, a co-author on the study and an associate professor in the SMU Earth Sciences Department.

“The DFW earthquake sequence began on Halloween in 2008 — before Oklahoma seismicity rates had notably increased,” said DeShon. “This study revisits what was technically the very first modern induced earthquake sequence in this region and shows that even though the wastewater injector in this case had been shut off very quickly, the injection activity still perturbed the fault, so that generated earthquakes even seven years later.”

That phenomenon is not unheard of. Seismologists saw that type of earthquake response from a rash of human-induced earthquakes in Colorado after wastewater injection during the 1960s at the Rocky Mountain Arsenal near Denver. Similarly in that case, injection was started and stopped, but earthquakes continued.

Such a possibility has not been well understood outside scientific circles, said DeShon. She is a member of the SMU seismology team that has studied and published extensively on their scientific findings related to the unusual spate of human-induced earthquakes in North Texas.

“The perception is that if the oil and gas wastewater injectors are leading to this, then you should just shut the injection wells down,” DeShon said. “But Paul’s study shows that there’s a lot to be learned about the physics of the process, and by monitoring continuously for years.”

Ogwari, DeShon and fellow SMU seismologist Matthew J. Hornbach reported the findings in the peer-reviewed Journal of Geophysical Research in the article “The Dallas-Fort Worth Airport Earthquake Sequence: Seismicity Beyond Injection Period.”

Known DFW Airport quakes number more than 400
The DFW Airport’s unprecedented earthquake clusters were the first ever documented in the history of the North Texas region’s oil-rich geological system known as the Fort Worth Basin. The quakes are also the first of multiple sequences in the basin tied to large-scale subsurface disposal of waste fluids from oil and gas operations.

The DFW Airport earthquakes began in 2008, as did high-volume wastewater injection of brine. Most of the seismic activity occurred in the first two months after injection began, primarily within .62 miles, or 1 kilometer, from the well. Other clusters then migrated further to the northeast of the well over the next seven years. The quakes were triggered on a pre-existing regional fault that trends 3.7 miles, or 6 kilometers, northeast to southwest.

Ogwari, a post-doctoral researcher in the SMU Roy M. Huffington Earth Sciences Department in Dedman College, analyzed years of existing seismic data from the region to take a deeper look at the DFW Airport sequence, which totaled 412 earthquakes through 2015.

Looking at the data for those quakes, Ogwari discovered that they had continued for at least seven years into 2015 along 80% of the fault, even though injection was stopped after only 11 months in August of 2009.

Rate of quakes declined, but magnitude has never lessened
In another important finding from the study, Ogwari found that the magnitude of the DFW Airport earthquakes didn’t lessen over time, but instead held steady. Magnitude ranged from 0.5 to 3.4, with the largest one occurring three years after injection at the well was stopped.

“What we’ve seen here is that the magnitude is consistent over time within the fault,” Ogwari said. “We expect to see the bigger events during injection or immediately after injection, followed by abrupt decay. But instead we’re seeing the fault continue to produce earthquakes with similar magnitudes that we saw during injection.”

While the rate of earthquakes declined — there were 23 events a month from 2008 to 2009, but only 1 event a month after May 2010 — the magnitude stayed the same. That indicates the fault doesn’t heal completely.

“We don’t know why that is,” Ogwari said. “I think that’s a question that is out there and may need more research.”

More monitoring needed for human-induced quakes
Answering that question, and others, about the complex characteristics and behavior of faults and earthquakes, requires more extensive monitoring than is currently possible given the funding allotted to monitor quakes.

Monitoring the faults involves strategically placed stations that “listen” and record waves of intense energy echoing through the ground, DeShon said.

The Fort Worth Basin includes the Barnett shale, a major gas producing geological formation, atop the deep Ellenberger formation used for wastewater storage, which overlays a granite basement layer. The ancient Airport fault system extends through all units.

Friction prevented the fault from slipping for millions of years, but in 2008 high volumes of injected wastewater disturbed the Airport fault. That caused the fault to slip, releasing stored-up energy in waves. The most powerful waves were “felt” as the earth shaking.

“The detailed physical equations relating wastewater processes to fault processes is still a bit of a question,” DeShon said. “But generally the favored hypothesis is that the injected fluid changes the pressure enough to change the ratio of the downward stress to the horizontal stresses, which allows the fault to slip.”

Earthquakes in North Texas were unheard of until 2008, so when they began to be felt, seismologists scrambled to install monitors. When the quakes died down, the monitoring stations were removed.

“As it stands now, we miss the beginning of the quakes. The monitors are removed when the earthquakes stop being felt,” DeShon said. “But this study tells us that there’s more to it than the ‘felt’ earthquakes. We need to know how the sequences start, and also how they end. If we’re ever going to understand what’s happening, we need the beginning, the middle — and the end. Not just the middle, after they are felt.”

Innovative method tapped for studying earthquake activity
Monitors the SMU team installed at the DFW Airport were removed when seismic activity appeared to have died down in 2009.

Ogwari hypothesized he could look at historical data from distant monitoring stations still in place to extract information and document the history of the DFW Airport earthquakes.

The distant stations are a part of the U.S. permanent network monitored and maintained by the U.S. Geological Survey. The nearest one is 152 miles, 245 kilometers, away.

Earthquake waveforms, like human fingerprints, are unique. Ogwari used the local station monitoring data to train software to identify DFW earthquakes on the distant stations. Ogwari took each earthquake’s digital fingerprint and searched through years of data, cross-correlating waveforms from both the near and regional stations and identified the 412 DFW Airport events.

“The earthquakes are small, less than magnitude three,” DeShon said. “So on the really distant stations it’s like searching for a needle in a haystack, sifting them from all the other tiny earthquakes happening all across the United States.”

Each path is unique for every earthquake, and seismologists record each wave’s movement up and down, north to south, and east to west. From that Ogwari analyzed the evolution of seismicity on the DFW airport fault over space and time. He was able to look at data from the distant monitors and find seismic activity at the airport as recent as 2015.

“Earthquakes occurring close in space usually have a higher degree of similarity,” Ogwari said. “As the separation distance increases the similarity decreases.”

To understand the stress on the fault, the researchers also modeled the location and timing of the pressure in the pores of the rock as the injected water infiltrated.

For the various earthquake clusters, the researchers found that pore pressure increased along the fault at varying rates, depending on how far the clusters were from the injection well, the rate and timing of injection, and hydraulic permeability of the fault.

The analysis showed pore-pressure changes to the fault from the injection well where the earthquakes started in 2008; at the location of the May 2010 quakes along the fault; and at the northern edge of the seismicity.

Will the DFW Airport fault continue to slip and trigger earthquakes?

“We don’t know,” Ogwari said. “We can’t tell how long it will continue. SMU and TexNet, the Texas Seismic Network, continue to monitor both the DFW Airport faults and other faults in the Basin.” — Margaret Allen, SMU

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Exploring the mysteries of the universe: Reality in the Shadows

New knowledge has caused us to reconsider many previous conclusions about what the universe is and how it works.

Despite centuries of scientific advancements, there is much about the universe that remains unknown. New knowledge and discoveries in the last 20 years have challenged previously accepted ideas and theories that were once regarded as scientific truth and have subjected them to increasing scrutiny.

These additions to our knowledge have caused scientists to reconsider many previous conclusions about what the universe is and how it works.

““Reality in the Shadows”” or “What the Heck’s the Higgs?” is a new book that explores the concepts that shape our current understanding of the universe and the frontiers of our knowledge of the cosmos.

The authors — two physicists and an engineer — tell us in a manner that non-scientists can readily follow, why studies have moved to superstring theory/M-theory, ideas about extra dimensions of space, and ideas about new particles in nature to find answers. It also explores why these ideas are far from established as accurate descriptions of reality.

“Our book explains how we know what we know about the universe, what we don’t know, and what we wish we did know,” said co-author Stephen Sekula, an associate professor of Physics at SMU. A physicist, Sekula conducts research into the Higgs Boson at the energy frontier on CERN’s ATLAS Experiment.

The book was initiated by Frank Blitzer, an engineer who participated on national space programs like Apollo and Patriot, several years ago, Sekula said. He was joined by co-author S. James Gates Jr., well known for his work on supersymmetry, supergravity and superstring theory, a few years ago.

“Frank and Jim sought additional input to help complete the book, and serendipitously Frank’s grandson, Ryan, was an SMU undergraduate and Hunt Scholar who helped connect them to me,” Sekula said. “After over an additional year of work, the book was completed.”

The foundations of modern physics rest on ideas that are over 100 years old and battle-tested, Sekula said.

“But nature has offered us new puzzles that have not yet been successfully explained by those ideas,” he added. “Perhaps we don’t yet have the right idea, or perhaps we haven’t searched deep enough into the cosmos. These are exciting times, with opportunities for a new generation of physicists who might crack these puzzles. Our book will help a curious reader to see the way in which knowledge was established, and encourage them to be engaged in solving the new mysteries.”

“Reality in the Shadows,” available through YBK Publishers, describes how humanity came to learn the workings of the universe as groundwork for the science that found the Higgs particle. Now scientists are hunting for the explanations for dark matter and the accelerated expansion of the cosmos, as well as for the many new questions the Higgs Boson itself has raised.

Scientists have recently discovered colliding black holes and neutron stars, that there is more non-luminous matter (dark matter) in the universe than the ordinary stuff of everyday life, and that the universe seems to grow larger each second at a faster and faster rate. Readers will learn how scientists discern such features of the universe and begin to see how to think beyond what is known to what is not yet known.

Throughout the book are descriptions of important developments in theoretical physics that lead the reader to a step-by-step understanding.

Sekula teaches physics and conducts research at ATLAS. He contributed to the measurement of decay modes of the Higgs boson and to the measurement of its spin-parity quantum numbers. Complementary to these efforts, he has worked with colleagues on the ATLAS Experiment to search for additional Higgs bosons in nature, providing intellectual leadership and direct involvement in several searches.

Gates was named 2014 “Scientist of the Year” by the Harvard Foundation. He was elected to the prestigious National Academy of Sciences in 2013 and received the 2013 National Medal of Science, the highest recognition given to scientists by the United States.

Gates has been featured on many TV documentary programs on physics, including “The Elegant Universe,” “Einstein’s Big Idea,” “Fabric of the Cosmos” and “The Hunt for the Higgs.” His DVD series, “Superstring Theory: The DNA of Reality,” makes the complexities of unification theory comprehensible.

Blitzer has more than 50 years of experience in engineering, program management, and business development and participated on national space programs, and The Strategic Defense Initiative (SDI), holding several patents in guidance and control. He has spent more than 20 years in independent research of the subject of the book.

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Scientific American: Drilling Reawakens Sleeping Faults in Texas, Leads to Earthquakes

For 300 million years faults showed no activity, and then wastewater injections from oil and gas wells came along. Study authors took a different approach in the new work — they hunted for deformed faults below Texas.

Science journalist Anna Kuchment covered the landmark earthquake research of a team of SMU geophysicists led by SMU Associate Professor Beatrice Magnani in the SMU Department of Earth Sciences. Kuchment wrote Drilling Reawakens Sleeping Faults in Texas, Leads to Earthquakes for Scientific American.

The SMU researchers tapped seismic data to analyze earthquakes in Texas over the past decade.

The results of the analysis showed that human activity is causing the earthquakes as a result of movement in faults that have been silent for at least 300 million years, until recent injection of oil and gas wastewater.

The article by Kuchment, “Drilling Reawakens Sleeping Faults in Texas, Leads to Earthquakes,” published Nov. 24, 2017.

Read the full story.

EXCERPT:

By Anna Kuchment
Scientific American
Since 2008, Texas, Oklahoma, Kansas and a handful of other states have experienced unprecedented surges of earthquakes. Oklahoma’s rate increased from one or two per year to more than 800. Texas has seen a sixfold spike. Most have been small, but Oklahoma has seen several damaging quakes stronger than magnitude 5. While most scientists agree that the surge has been triggered by the injection of wastewater from oil and gas production into deep wells, some have suggested these quakes are natural, arising from faults in the crust that move on their own every so often. Now researchers have traced 450 million years of fault history in the Dallas-Fort Worth area and learned these faults almost never move. “There hasn’t been activity along these faults for 300 million years,” says Beatrice Magnani, a seismologist at Southern Methodist University in Dallas and lead author of a paper describing the research, published today in Science Advances. “Geologically, we usually define these faults as dead.”

Magnani and her colleagues argue that these faults would not have produced the recent earthquakes if not for wastewater injection. Pressure from these injections propagates underground and can disturb weak faults. The work is another piece of evidence implicating drilling in the quakes, yet the Texas government has not officially accepted the link to one of its most lucrative industries.

Magnani and her colleagues studied the Texas faults using images of the subsurface similar to ultrasound scans. Known as seismic reflection data, the images are created by equipment that generates sound waves and records the speeds at which the waves bounce off faults and different rock layers deep within the ground. Faults that have produced earthquakes look like vertical cracks in a brick wall, where one side of the wall has sunk down a few inches so the rows of bricks no longer line up. Scientists know the age of each rock layer—each row of bricks–based on previous studies that have used a variety of dating techniques.

Read the full story.

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The Washington Post: Oil and gas industry is causing Texas earthquakes, a ‘landmark’ study suggests

The study authors took a different approach in the new work — they hunted for deformed faults below Texas.

The Washington Post covered the landmark earthquake research of a team of SMU geophysicists led by SMU Associate Professor Beatrice Magnani in the SMU Department of Earth Sciences.

The researchers tapped seismic data to analyze earthquakes in Texas over the past decade.

The results of the analysis showed that human activity is causing the earthquakes as a result of movement in faults that have been silent for at least 300 million years, until recent injection of oil and gas wastewater.

The article by journalist Ben Guarino, “Oil and gas industry is causing Texas earthquakes, a ‘landmark’ study suggests,” published Nov. 24, 2017.

Read the full story.

EXCERPT:

By Ben Guarino
The Washington Post
An unnatural number of earthquakes hit Texas in the past decade, and the region’s seismic activity is increasing. In 2008, two earthquakes stronger than magnitude 3 struck the state. Eight years later, 12 did.

Natural forces trigger most earthquakes. But humans are causing earthquakes, too, with mining and dam construction the most frequent suspects. There has been a recent increase in natural gas extraction — including fracking, or hydraulic fracturing, but other techniques as well — which produces a lot of wastewater. To get rid of it, the water is injected deep into the ground. When wastewater works its way into dormant faults, the thinking goes, the water’s pressure nudges the ancient cracks. Pent-up tectonic stress releases and the ground shakes.

But for any given earthquake, it is virtually impossible to tell whether humans or nature triggered the quake. There are no known characteristics of a quake, not in magnitude nor in the shape of its seismic waves, that provide hints to its origins.

“It’s been a head-scratching period for scientists,” said Maria Beatrice Magnani, who studies earthquakes at Southern Methodist University in Dallas. Along with a team of researchers at the U.S. Geological Survey, Magnani, an author of a new report published Friday in the journal Science Advances, attempted to better identify what has been causing the rash of Texas quakes.

A cluster of earthquakes around a drilling project can, at best, suggest a relationship. “The main approach has been to correlate the location to where there has been human activity,” said Michael Blanpied, a USGS geophysicist and co-author of the new study.

Read the full story.