Junyu Zhang selected as Eberly College of Science’s Fall 2022 Student Marshal


Junyu Zhang of Chongqing, China, will be honored as the student marshal for the Eberly College of Science during Penn State’s fall commencement ceremonies on Saturday, Dec. 17, on the University Park campus.

Zhang will graduate with a 4.0 grade point average and bachelor’s degrees in astronomy, physics, and mathematics. He is a Schreyer Scholar in the Schreyer Honors College and has been a member of the Dean’s List every semester. Zhang has been honored with several awards and scholarships, including the John and Elizabeth Holmes Teas Scholarship from 2021 to 2022, the Bert Elsbach Honors Scholarship from 2020 to 2021, the Evan Pugh Scholar Senior Award in 2021, and the President’s Freshman Award in 2020.

“It is my great honor to be selected as student marshal for the Eberly College of Science,” he said. “I could not have achieved such a huge accomplishment without the support of my family, my mentors, my professors, and my friends. Therefore, I would like to share this honor with them.”

While at Penn State, Zhang conducted research with both Joel Leja, assistant professor of astronomy and astrophysics, and Niel Brandt, Verne M. Willaman Professor of Astronomy & Astrophysics and professor of physics. In his work with Leja, Zhang used a computer code called Prospector to investigate various wavelengths of light that are emitted by galaxies in order to identify markers that might distinguish galaxies that normally form stars from “rejuvenating galaxies” that fully quench—stop producing stars—and then become star-forming once more. Because rejuvenating galaxies are rare in the universe, these studies may help astronomers better understand the conditions under which stars and galaxies form. With Brandt, Zhang used data from X-ray surveys to identify active galactic nuclei found at the centers of some galaxies that have high redshift—the light they give off is skewed toward the red end of the spectrum due to their distance from Earth—and to better understand how they affect their host galaxies.

“The most important lesson that I will take with me from my time at Penn State is to follow your heart,” Zhang said. “One of the bravest decisions I ever made was to transfer to Penn State and change my major. Although I lost almost all three years I spent at my original university, I am now able to study what I love and achieve such an accomplishment like becoming a student marshal.”

After graduation, Zhang plans to continue his research in astronomy by pursuing a graduate degree.

Zhang is a graduate of Chongqing Nankai Secondary School in Chongqing, China. His parents are Li Mu and Kedi Zhang.

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Rare Cosmic Explosion Blasts Hole in Established Science


On Dec. 11, 2021, the NASA’s Neil Gehrels Swift Observatory, which has its Mission Operations Center at Penn State, detected a blast of high-energy light from a galaxy roughly 1 billion light-years away. The event, which was simultaneously detected by Fermi Gamma-ray Space Telescope, brings into question what was thought to be settled science concerning gamma-ray bursts (GRBs), the most energetic explosions in the universe.

“It was something we had never seen before,” said Simone Dichiara, assistant research professor of astronomy and astrophysics at Penn State and member of the Swift team. “We knew it wasn’t associated with a supernova, the death of a massive star, because it was too close. It was a completely different kind of optical signal, one that we associate with a kilonova, the explosion triggered by colliding neutron stars.”

The Swift team was able to rapidly identify the explosion’s location, in the constellation Boötes, enabling other facilities to quickly respond with follow-up observations. Their observations have provided the earliest look yet at the first stages of a kilonova, according to a NASA release. Their findings were published today (Dec. 7) in the journal Nature.

Gamma-ray bursts come in two varieties: long and short. Scientists previously understood long GRBs, which last a couple of seconds to one minute, as forming when a super massive star explodes as a supernova. Short GRBs, which last less than two seconds, were previously thought to only occur when two compact objects — like two neutron stars or a neutron star and a black hole — collide to form a kilonova.

The revelation that a kilonova could trigger a long gamma-ray burst rewrites the decades-long paradigm of cosmic explosions: that long GRBs are strictly the signature of the death of massive stars, Dichiara explained. The discovery means not all long GRBs are made by supernovae, some are produced by the merger of neutron stars.

“This event was a game-changer that showed to us how our well-established knowledge of the universe was in fact only a partial and incomplete view,” said Eleonora Troja, an astronomer at the University of Rome Tor Vergata and lead author on the paper. “This result was hard to digest at first and we spent months trying to figure out alternative explanations, but in the end this is the only one that works well. Although we have been studying GRBs for decades, it is awesome to see how the universe can surprise us in the most unexpected ways.”

The work was supported by the European Research Council through the Consolidator grant BHianca and by the National Science Foundation.

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Bright light from early universe 'opens new chapter in astronomy'


UNIVERSITY PARK, Pa. — An unexpectedly rich array of early galaxies that was largely hidden until now has been observed by researchers using data from NASA’s James Webb Space Telescope.

The researchers found two exceptionally bright galaxies that existed approximately 350 and 450 million years after the big bang. Their extreme brightness is puzzling to astronomers and challenges existing models of galaxy formation.

“These objects are remarkable because they are far brighter than we would expect from our models of how galaxies form,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State, who developed the code used to analyze light from the distant galaxies.

As a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics, Leja developed code capable of making sense of infrared data from distant galaxies, such as those imaged by Webb, proving that they are in fact our first glimpses of the very early universe.

“The code combines models of all the things that live in galaxies and interprets the light we observe from them,” said Leja. “This includes things like stars of various ages and elemental compositions, cosmic dust that blocks the light we see from stars, emission from gaseous nebulae, and so on.”

Two research papers, one led by Marco Castellano of the National Institute for Astrophysics in Rome, Italy, and another by Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics and the Massachusetts Institute of Technology with Leja as co-author, have been published in the Astrophysical Journal Letters. The two papers describe the bright celestial objects, which both teams discovered separately in quick succession just days after Webb officially started science operations.

“With Webb, we were amazed to find the most distant starlight that anyone had ever seen, just days after Webb released its first data,” Naidu said in a NASA news release.

With just four days of analysis, the researchers found two exceptionally bright galaxies. They determined the young galaxies transformed gas into stars extremely rapidly, meaning the onset of stellar birth may have started just 100 million years after the big bang, roughly 13.8 billion years ago. The researchers also determined the two galaxies existed approximately 450 and 350 million years after the big bang, though future spectroscopic measurements with Webb will help confirm their findings.

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Tracing the Origins of Rare Cosmic Explosions


The galactic homes of 84 short gamma-ray bursts (sGRBs)—produced by the collision of two neutron stars—have now been pinpointed in what is the most extensive inventory to date. A team that includes astronomers from Penn State used information from several highly sensitive instruments at the W.M. Keck Observatory, Las Campanas Observatory, MMT Observatory, and Gemini Observatory, combined with some of the most sophisticated galaxy modeling ever used in the field to identify the sources of these sGRBs.

“At most, astronomers might detect about a dozen short gamma-ray bursts each year, and so far only one has a confirmed origin from a neutron star merger,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State and a member of the research team. “Their mysterious origins have led us to take a lateral approach by instead trying to understand the environments where these objects thrive. The resulting catalog greatly expands our knowledge of where sGRBs come from and will help astronomers determine their true origins.” 

SGRBs are momentary flashes of intense gamma-ray light emitted when two neutron stars collide. As an homage to the fact that sGRBs are among the brightest explosions in the universe, the team calls their catalog BRIGHT (Broadband Repository for Investigating Gamma-ray burst Host Traits) with all of their data and modeling products online for community use.

“This is the largest catalog of sGRB host galaxies to ever exist, so we expect it to be the gold standard for many years to come,” said Anya Nugent, an astronomy graduate student at Northwestern University who led the research, observational efforts with Keck and the MMT observatories, and one of the two publications on the study. 

While the gamma-rays from sGRBs last only seconds, the optical light that is also produced in the event can continue for hours before fading below detection thresholds, called an afterglow. SGRB afterglows were first discovered in 2005 by NASA’s Neil Gehrels Swift Observatory, whose mission operations center is located at Penn State. Since then, astronomers have spent the last 17 years trying to find out which galaxies these powerful bursts originated from, as the stars within a galaxy can give insight into the environmental conditions needed to produce these events and can connect them to their neutron star merger origins. The only sGRB with a confirmed neutron star merger origin, GRB 170817A, was detected just seconds after gravitational wave detectors observed the binary neutron star merger, GW170817.

“One way to better understand gamma ray bursts is to understand the types of ‘cosmic ecosystems’ which they tend to live in, meaning the gas and stars in the environment around them—their host galaxies,” said Leja. “We modeled the galaxies where these gamma-ray burst happened, including information about how many stars are in the galaxy, how it formed, how many heavy elements are there, and how much dust obscures our view of the galaxy. This allowed us to understand how galaxies where gamma-ray bursts explode are different than other galaxies.”

Learning about sGRB host galaxies is crucial to understanding the blasts themselves and offers clues about the types of stars that created them as well as their distance from Earth. Since neutron star mergers create heavy elements like gold and platinum, the data will also deepen scientists’ understanding of when precious metals were first created in the universe.

“Building this catalog and finally having enough host galaxies to see patterns and draw significant conclusions is exactly what the field needed to push our understanding of these fantastic events and what happens to stars after they die,” said Nugent.

“In a decade, the next generation of gravitational wave observatories will be able to detect neutron star mergers out to the same distances as we do sGRBs today. Thus, our catalog will serve as a benchmark for comparison to future detections of neutron star mergers,” added Wen-fai Fong, assistant professor of astronomy and physics at Northwestern University and lead author of one of the publications.

The first paper in the study

, published in The Astrophysical Journal, found that sGRBs occur at earlier times in the universe and at greater distances from their host galaxy’s centers than previously thought. Surprisingly, several of these explosions were found just outside their host galaxies as if they were “kicked out,” raising questions as to how they were able to travel that far.

Published in the same journal, the second research paper

in the study probed the characteristics of 69 of the identified sGRB host galaxies. The findings suggest about 85 percent of them are young, actively star-forming galaxies — a stark contrast to earlier studies that characterized the population of sGRB host galaxies as relatively old and approaching death. This means neutron star systems may form in a broad range of environments and many of them have quick formation-to-merger timescales.

Many questions remain about how neutron stars merge and how long the process takes. But observing sGRBs and their host galaxies provides one of the best perspectives to answer them and can offer more data about neutron star mergers and their hosts at much farther distances, and more frequently, than current gravitational wave detectors. This new sGRB host catalog will therefore serve as a vital reference point in the coming decade to understand the full evolution of these systems over cosmic time. 

The James Webb Space Telescope (JWST) is poised to further advance our understanding of neutron star mergers and how far back in time they began, as it will be able to detect the faintest host galaxies that exist at very early times in the universe.

“This field is so young— there is so much more to learn,” said Leja. “We hope that we can learn even more about the cosmic environment of sGRBs with near-future observatories, and in this way better understand what precipitates these mysterious explosions.”

In addition to Leja, the research team at Penn State also includes Derek Fox, associate professor of astronomy and astrophysics.

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Bright Light from Early Universe 'Opens New Chapter in Astronomy'


UNIVERSITY PARK, Pa. — An unexpectedly rich array of early galaxies that was largely hidden until now has been observed by researchers using data from NASA’s James Webb Space Telescope.

The researchers found two exceptionally bright galaxies that existed approximately 350 and 450 million years after the big bang. Their extreme brightness is puzzling to astronomers and challenges existing models of galaxy formation.

“These objects are remarkable because they are far brighter than we would expect from our models of how galaxies form,” said Joel Leja, assistant professor of astronomy and astrophysics at Penn State, who developed the code used to analyze light from the distant galaxies.

As a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics, Leja developed code capable of making sense of infrared data from distant galaxies, such as those imaged by Webb, proving that they are in fact our first glimpses of the very early universe.

“The code combines models of all the things that live in galaxies and interprets the light we observe from them,” said Leja. “This includes things like stars of various ages and elemental compositions, cosmic dust that blocks the light we see from stars, emission from gaseous nebulae, and so on.”

Two research papers, one led by Marco Castellano of the National Institute for Astrophysics in Rome, Italy, and another by Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics and the Massachusetts Institute of Technology with Leja as co-author, have been published in the Astrophysical Journal Letters. The two papers describe the bright celestial objects, which both teams discovered separately in quick succession just days after Webb officially started science operations.

“With Webb, we were amazed to find the most distant starlight that anyone had ever seen, just days after Webb released its first data,” Naidu said in a NASA news release.

With just four days of analysis, the researchers found two exceptionally bright galaxies. They determined the young galaxies transformed gas into stars extremely rapidly, meaning the onset of stellar birth may have started just 100 million years after the big bang, roughly 13.8 billion years ago. The researchers also determined the two galaxies existed approximately 450 and 350 million years after the big bang, though future spectroscopic measurements with Webb will help confirm their findings.

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Icecube Neutrinos Give First Glimpse Into the Inner Depths of an Active Galaxy


UNIVERSITY PARK, Pa. — For the first time, an international team including Penn State scientists has found evidence of high-energy neutrino emission from Messier 77, also known as NGC 1068, an active galaxy in the constellation of Cetus.

Neutrinos are fundamental particles with no charge and almost no mass, and they rarely interact with other matter. High-energy neutrinos — like those detected here with energies in the teraelectron volt (TeV), or trillion-electron volt, range — can travel for billions of light-years through space without being deflected or absorbed. Thus, while they are extremely difficult to detect, they can provide accurate information about the distant universe, especially when the information the carry can be combined with information from other cosmic signals in what is called “multimessenger” astronomy.

The detection was made by the IceCube Neutrino Observatory, a massive neutrino telescope encompassing one billion tons of instrumented ice at depths from 1.5 to 2.5 kilometers below Antarctica’s surface near the South Pole.

“IceCube is a veritable discovery machine,” said Doug Cowen, professor of physics and of astronomy and astrophysics at Penn State and a long-time IceCube collaborator. “The huge detector has lived up to its promise to launch the brand-new field of high energy neutrino astronomy, and then some, now by giving us glimpses behind a black hole’s black-out curtain of matter. IceCube has once again proved that when humanity points a new instrument at the heavens — starting with Galilleo’s first telescope — our knowledge of the universe around us increases by leaps and bounds.”

This unique telescope, which explores the farthest reaches of our universe using weakly interacting neutrinos instead of light, recorded the first observation of a potential source of high-energy astrophysical neutrinos in 2017. The source of these first observations is the known blazar TXS 0506+056, which is situated in the night sky just off the left shoulder of the constellation Orion and about 4 billion light-years from Earth.

Blazars are very luminous and distant active galaxies with a powerful, relativistic jet of particles pointing directly at us. Unlike NGC 1068, the blazar TXS 0506+056 had not been studied much before the multimessenger detection of neutrinos and high-energy electromagnetic radiation that allowed follow-up measurements by almost 20 telescopes around the world. Now, the observation of neutrino emission from a different type of active galaxy brings us closer to understanding the supermassive black holes powering them.

“One neutrino can single out a source. But only an observation with multiple neutrinos will reveal the obscured core of the most energetic cosmic objects,” said Francis Halzen, a professor of physics at the University of Wisconsin–Madison, the headquarters of the National Science Foundation (NSF)´s Antarctic neutrino facility, and principal investigator of IceCube. “IceCube has accumulated some 80 neutrinos of TeV energy from NGC 1068, which are not yet enough to answer all our questions, but they definitely are the next big step towards the realization of neutrino astronomy.”

The results appear Nov. 4 in the journal Science.

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Swift telescope captures brightest gamma-ray burst ever recorded


On October 9, 2022, an unusually bright and long-lasting gamma-ray burst—the most powerful type of explosion in the universe—was detected by the Neil Gehrels Swift Observatory, whose Mission Operations Center is located at Penn State and led by Professor of Astronomy and Astrophysics John Nousek. The burst—the brightest ever recorded, called GRB 221009A—originated from the death of a massive star about two billion light years away, likely collapsing to form a black hole and sending gamma rays, X-rays, and other particles into space.

A striking image of the burst’s afterglow was captured by Swift’s X-Ray Telescope, which is led by Penn State Research Professor of Astronomy and Astrophysics Jamie Kennea and was originally built under the leadership of Professor of Astronomy and Astrophysics David Burrows. Swift and other observatories are continuing to observe the aftermath of the event, which could help provide new insights into stellar collapse, the birth of a black hole, and the conditions in distant galaxies.

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The Hobby-Eberly Telescope reaches 25th anniversary milestone


One of the world’s largest optical telescopes, the Hobby-Eberly telescope (HET) at the University of Texas at Austin’s McDonald Observatory, is marking 25 years of investigating the mysteries of the cosmos. The HET’s unique and innovative design was developed by Penn State professors Lawrence W. Ramsey, who has served as the HET’s project scientist and as the chairman of its board of directors, and Daniel W. Weedman in the early 1980s.

The telescope is named for Robert E. Eberly, a Penn State alumnus and benefactor, for whom Penn State’s Eberly College of Science is also named, and former Texas Lieutenant-Governor William P. Hobby.

“This year marks an important milestone for the Hobby-Eberly telescope,” said Taft Armandroff, the Frank and Susan Bash Endowed Chair at UT Austin, Director of McDonald Observatory, and HET board chair. “The HET provides the resources that our faculty and researchers from many different institutions use to do cutting-edge science.”

First dedicated in 1997, the HET is currently a collaboration of four institutions: the University of Texas at Austin, Penn State, the University of Munich, and the University of Goettingen. The telescope, which has an 11-meter (433-inch) primary mirror, received a major upgrade in 2016, expanding its field-of-view to capture a section of the night sky 120-times larger than before. This capability and new instruments were celebrated in a re-dedication event in 2017.

“In addition to its enormous light-gathering power, the HET’s scheduling system allows it to rapidly respond to unusual, transient events in the heavens,” said Ramsey, emeritus professor of astronomy and astrophysics and Eberly College of Science Distinguished Senior Scholar. “This combination allows HET to address a wide range of scientific questions, ranging from exoplanets to the large-scale structure of the universe. In the HET’s first quarter-century, over 450 peer-reviewed papers relied on HET data.”

The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) is an international collaboration that is probing dark energy, the mysterious force that is accelerating the expansion of the universe, to build an extensive three-dimensional map of the universe when it was but a fraction of its current age. By training the HET on two regions of the sky, one near the Big Dipper and one near Orion, the telescope is capturing the cosmic fingerprint of the light from 2.5 million galaxies. Astronomers are using the Visible Integral-field Replicable Unit Spectrograph, which can simultaneously obtain over 30,000 spectra in a 20-minute exposure, to address a number of fundamental questions, in particular why the expansion of the universe is speeding up over time.

“The HETDEX program involves not only the four university partners but dozens of additional scientists at several institutions from around the world,” said Donald Schneider, distinguished professor in the Department of Astronomy and Astrophysics at Penn State and a HET board member.

HET has played an integral role in finding Earth-sized planets beyond our solar system. The Habitable Zone Planet Finder (HPF), developed by a team of scientists led by Penn State Professor of Astronomy and Astrophysics Suvrath Mahdevan, aims to identify so-called “Goldilocks planets,” exoplanets capable of supporting liquid water on their surfaces. One discovery involved K2-25b, a planet the size of Neptune orbiting a cool star. Using high-time resolution HPF spectroscopy of the system when the planet passed between Earth and the star, astronomers were able to determine the angle between the star’s equator and the orbit of the planet, which offers insights into the formation and evolution of planetary systems.

“A lot of the public thinks science has these eureka moments, but most major scientific discoveries are met with ‘hmm, that’s funny,’” said Bill Cochran, research professor at UT Austin and chair of the HET Users Committee. “Whether or not a planet is habitable is not the right question. I am interested in how the planet evolved, and I want to use the findings with the HPF to pursue these questions with my colleagues in different disciplines.”

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Congratulations to Miguel Mostafa


Miguel Mostafá, professor of physics and of astronomy and astrophysics and associate dean for research and innovation, is one of three members of the Eberly College of Science to receive the Distinguished Faculty Mentoring Award in 2022. The award was created in 2019 to honor faculty members in the college for their outstanding work in mentoring students, postdocs, and faculty.

Mostafá was recognized for his stellar record of mentoring individuals at the undergraduate, graduate, postdoc, and most recently, junior faculty level. He leads by example, investing time and energy in the service of his mentees. According to one nominator, he “genuinely cares about the well-being and development of his mentees, encouraging them through difficult times, helping them maintain self-efficacy, and providing perspective and specific career advice.”

“He helps his mentees develop ideas constructively,” said another nominator. “For example, by brainstorming one-on-one and in group meetings, suggesting a diverse perspective, and always providing prompt and detailed feedback on their own ideas.”

Mostafá also encourages his mentees to take advantage of professional development opportunities, and many of his undergraduate and graduate students have gone on to win scholarships, participate in off-campus research experiences, and be accepted to excellent graduate programs or pursue postdoctoral research.

His mentoring is not limited to members of his own research group. For example, Mostafá is a faculty mentor for students in the Women in Science and Engineering Research (WISER) and Minority Undergraduate Research Experience (MURE) programs for NASA’s Pennsylvania Space Grant Consortium. He is also the faculty adviser of the Latin American Graduate Student Association at Penn State, and he has served as a mentor to many students from underrepresented groups at Penn State through the Millennium Scholars Program and Summer Research Opportunities Program.

“I know it is not an accident that many of his students are female or underrepresented students, as he’s shown a dedication to increasing the diversity of our research environment,” said one nominator.

Notably, Mostafá also mentors postdocs, providing training not only in research skills, but also in the transition to a career as independent researchers. He also helps junior faculty with their own early career development, including by providing advice on grant proposals, teaching, and managing a large research group. Importantly, Mostafá uses the opportunity to teach his mentees how to be good mentors themselves.

“I have not seen another colleague more worthy of such an award,” added a nominator.

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New TIGER approved for deployment to the International Space Station


A team of physicists that includes researchers at Penn State is developing a new experiment envisioned for the International Space Station (ISS) as part of NASA’s Astrophysics Pioneers Program. The new experiment, the Trans-Iron Galactic Element Recorder for the International Space Station (TIGERISS), will be designed to measure the abundances of ultra-heavy galactic cosmic rays—high-energy particles that have been rapidly accelerated from a star’s violent collapse, called a supernova, or other cosmic events such as the merger of two neutron stars. By measuring the quantity of each atomic element in cosmic rays, scientists gain information about where they could have originated.

TIGERISS is an evolution of the TIGER and SuperTIGER balloon-borne instruments, developed by scientists at Washington University, NASA Goddard, Caltech and others over the past three decades, with the Penn State contingent invited to participate in the next phase of the science program. “We are excited to join old friends from the cosmic-ray ballooning community in investigating the rare but fascinating ultra-heavy cosmic rays,” said Stephane Coutu, professor of physics and of astronomy and astrophysics and the Penn State lead investigator for the TIGERISS program. “The origin of the heavy elements of the periodic table, such as the gold you might wear around your neck or finger, ultimately links back to intriguing, violent and exotic astrophysical phenomena.”

Other Penn State team members include physics research professors Samuel Isaac Mognet and Tyler Anderson. Together the Penn State team has decades of experience successfully developing detector elements for space-rated instruments flown on high-altitude balloons or to the ISS where TIGERISS will be deployed in a few years.

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NASA selects STAR-X for $3M mission concept study


STAR-X, the Survey and Time-domain Astrophysical Research Explorer, a proposed NASA Medium-Class Explorer (MIDEX) mission that includes Penn State astronomer Niel Brandt, has been selected by the NASA Explorers Program for further study. STAR-X is one of two proposed MIDEX missions that will receive $3 million for a nine-month detailed study of mission requirements. At the end of this period, one of the proposed missions will be selected for a target launch date in 2027-2028 and be eligible for up to $300 million in additional funding.

Comprised of an X-ray telescope, an ultraviolet (UV) telescope, and a responsive spacecraft, STAR-X is designed to conduct time-domain surveys, which study how astronomical objects change with time, and to respond rapidly to transient cosmic events discovered by other observatories such as LIGO, Rubin LSST, the Roman Space Telescope, and the Square Kilometer Array. The mission is led by Principal Investigator William Zhang at NASA’s Goddard Space Flight Center (GSFC) in Greenbelt, Maryland. Penn State’s Brandt, who is the Verne M. Willaman Professor of Astronomy and Astrophysics and Professor of Physics, is involved in planning the STAR-X cosmic X-ray surveys, active galaxy studies, and fast X-ray transient studies.

“I can’t wait to use STAR-X to investigate the first supermassive black holes and understand mysterious, explosive X-ray transient sources,” said Brandt. “STAR-X will also provide the essential X-ray and UV follow-up capabilities for remarkable cosmic objects discovered by the Rubin LSST in optical light.”

The STAR-X spacecraft would be able to turn rapidly to point a sensitive wide-field X-ray telescope and a UV telescope at transient cosmic sources, such as supernova explosions and feeding supermassive black holes. Deep X-ray surveys would map black holes and hot gas trapped in distant clusters of galaxies; combined with infrared observations from NASA’s upcoming Roman Space Telescope, these observations would trace how massive clusters of galaxies built up over cosmic history.

STAR-X would provide revolutionary capabilities including unprecedented X-ray and UV volumetric survey speed; a unique combination of large field-of-view, large X-ray collecting area, low background, and excellent imaging; increased sensitivity for characterizing diffuse emissions, and increased speed and sensitivity for the discovery of faint X-ray point sources. It fills the gap in X-ray and UV survey coverage, providing simultaneous X-ray and UV observations, which are among the earliest and most uniquely informative astrophysical signals that probe the inner regions around compact objects like black holes and neutron stars, and it complements optical, infrared, and gravitational wave facilities.

The mission’s Deputy Principal Investigator, Ann Hornschemeier, who is also Lab Chief for X-ray Astrophysics at GSFC, earned a Ph.D. in Astronomy and Astrophysics at Penn State, mentored by Brandt, in 2002.

“Ann is superb - a bundle of energy, and the right person to push STAR-X to succeed,” said Brandt.

NASA Explorer missions conduct focused scientific investigations and develop instruments that fill scientific gaps between the agency’s larger space science missions. The proposals were competitively selected based on potential science value and feasibility of development plans. The Explorers Program is the oldest continuous NASA program and is designed to provide frequent, low-cost access to space using principal investigator-led space science investigations relevant to the Science Mission Directorate’s astrophysics and heliophysics programs.

“NASA’s Explorers Program has a proud tradition of supporting innovative approaches to exceptional science, and these selections hold that same promise,” said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at NASA Headquarters in Washington. “From studying the evolution of galaxies to explosive, high-energy events, these proposals are inspiring in their scope and creativity to explore the unknown in our universe.”

Since the launch of Explorer 1 in 1958, which discovered the Earth’s radiation belts, the Explorers Program has launched more than 90 missions, including the Uhuru and Cosmic Background Explorer (COBE) missions that led to Nobel prizes for their investigators.

The program is managed by NASA Goddard for NASA’s Science Mission Directorate in Washington, which conducts a wide variety of research and scientific exploration programs for Earth studies, space weather, the solar system, and the universe. More information can be found at the Explorers Program website (https://explorers.gsfc.nasa.gov/).

Further technical details about the observatory are available at (http://star-x.xraydeep.org/observatory/).

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Dark Matter detector completes startup operations


Deep below the Black Hills of South Dakota in the Sanford Underground Research Facility (SURF), an innovative and uniquely sensitive dark matter detector—the LUX-ZEPLIN (LZ) experiment—has passed a check-out phase of startup operations and delivered its first results. The LZ experiment, which is designed to observe the mysterious and as-yet-undetected phenomenon known as dark matter, is led by Lawrence Berkeley National Lab (Berkeley Lab) in conjunction with an international team of 250 scientists and engineers from over 35 institutions including Penn State.

“Dark matter is a fundamental part of the universe, but because it does not emit, absorb, or scatter light, it cannot be observed in conventional ways,” said Carmen Carmona-Benitez, assistant professor of physics and the LZ principal investigator at Penn State. “I’m thrilled to see this complex detector ready to address the long-standing mystery of what dark matter is made of. The LZ team now has in hand the most ambitious instrument to do so!”

Dark matter’s presence and gravitational pull are fundamental to our understanding of the universe. For example, the presence of dark matter, estimated to be about 85 percent of the total mass of the universe, shapes the form and movement of galaxies, and it is invoked by researchers to explain what is known about the large-scale structure and expansion of the universe.

Dark Matter particles have never actually been detected—but perhaps not for much longer. The countdown may have started with results from LZ’s first 60 “live days” of testing. These data were collected over a three-and-a-half-month span of initial operations beginning at the end of December. This was a period long enough to confirm that all aspects of the detector were functioning well.

In a paper posted online July 7 on the experiment’s website (https://lz.lbl.gov/) and the online preprint archive arXiv.org, LZ researchers report that with results from the initial run, LZ is the world’s most sensitive dark matter detector.

“We plan to collect about 20 times more data in the coming years, so we’re only getting started,” said LZ Spokesperson Hugh Lippincott of the University of California Santa Barbara. “There’s a lot of science to do and it’s very exciting!”

A variety of cosmic particles collide with the Earth on a regular basis, and LZ is designed to detect theorized dark matter particles known as weakly interacting massive particles (WIMPs). The experiment is located about a mile underground to protect it from cosmic radiation at the Earth’s surface that could drown out dark matter signals.

The heart of the LZ dark matter detector is comprised of two nested titanium tanks filled with ten tons of very pure liquid xenon. When particles collide with xenon atoms, they produce visible scintillation or flashes of light, which are recorded by two arrays of photomultiplier tubes (PMTs), explained Aaron Manalaysay from Berkeley Lab who, as LZ physics coordinator, led the collaboration’s efforts to produce these first physics results, including calibration, understanding of the detector response, and sensitivity.

“Considering we just turned it on a few months ago and during COVID restrictions, it is impressive we have such significant results already,” Manalaysay said.

The collisions will also knock electrons off xenon atoms, sending them to drift to the top of the chamber under an applied electric field where they produce another flash permitting spatial event reconstruction.

“The characteristics of the light signals help determine the types of particles interacting in the xenon, allowing us to separate backgrounds and potential dark matter events,” said Luiz de Viveiros, assistant professor of physics at Penn State, whose team is responsible for modeling and monitoring background signals in the detector.

“Lots of subsystems started to come together as we started taking data for detector commissioning, calibrations and science running. Turning on a new experiment is challenging, but we have a great LZ team that worked closely together to get us through the early stages of understanding our detector,” said David Woodward, assistant research professor of physics at Penn State and the experiment run coordinator.

The take home message from this successful startup: “We’re ready and everything’s looking good,” said Berkeley Lab Senior Physicist and past LZ Spokesperson Kevin Lesko. “It’s a complex detector with many parts to it and they are all functioning well within expectations,” he said.

The design, manufacturing, and installation phases of the LZ detector were led by Berkeley Lab project director Gil Gilchriese. The LZ operations manager, Berkeley Lab’s Simon Fiorucci, said the onsite team deserves special praise at this startup milestone, given that the detector was transported underground late in 2019, just before the onset of the COVID-19 pandemic. He said with travel severely restricted, only a few LZ scientists could make the trip to help on site. The team in South Dakota took excellent care of LZ.

“I’d like to second the praise for the team at SURF and would also like to express gratitude to the large number of people who provided remote support throughout the construction, commissioning and operations of LZ, many of whom worked full time from their home institutions making sure the experiment would be a success and continue to do so now,” said Tomasz Biesiadzinski of the SLAC National Accelerator Laboratory and the LZ detector operations manager.

“The entire SURF team congratulates the LZ Collaboration in reaching this major milestone,” said Mike Headley, executive director of SURF Lab. “The LZ team has been a wonderful partner and we’re proud to host them at SURF.”

With confirmation that LZ and its systems are operating successfully, Carmona-Benitez said, it is time for full-scale observations to begin in hopes that a dark matter particle will collide with a xenon atom in the LZ detector soon!

LZ is supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics and the National Energy Research Scientific Computing Center, a DOE Office of Science user facility. LZ is also supported by the Science & Technology Facilities Council of the United Kingdom; the Portuguese Foundation for Science and Technology; and the Institute for Basic Science, Korea. Over 35 institutions of higher education and advanced research provided support to LZ. The LZ collaboration acknowledges the assistance of the Sanford Underground Research Facility.

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Hubble Finds Isolated Black Hole Roaming Our Milky Way Galaxy


Though an estimated 100 million black holes are predicted to roam among the stars in our Milky Way galaxy, astronomers have never conclusively identified an isolated black hole – until now. Previously, black holes with the mass of the newly identified one had only been detected in binary systems in which the black hole is gravitationally bound to a normal, visible star. Now, following six years of meticulous observations, NASA’s Hubble Space Telescope has provided, for the first time ever, strong evidence for a lone black hole drifting through interstellar space.

A paper describing the discovery, by a team that includes Penn State astronomer Howard Bond, has been accepted for publication in the Astrophysical Journal.

“Black holes have been in the news recently as a spectacular image of the black hole at the center of our Milky Way galaxy was released a few weeks ago,” said Bond, professor of practice in astronomy and astrophysics at Penn State. “This black hole has a mass of 4 million times that of our Sun; it’s what’s called a supermassive black hole. Our object, by contrast, has a mass of only 7.1 times that of the Sun. It’s a ‘stellar-mass’ black hole. There are very likely many of these objects in the Milky Way, but they are extremely difficult to detect since they emit no light. Ours is the first one to be identified based on the black hole deflecting the image of a background star that it passed closely in front of.”

The black hole that was detected lies about 5,000 light-years away, in the Carina-Sagittarius spiral arm of our galaxy. For context, the nearest star to our solar system, Proxima Centauri, is a little over 4 light-years away.

Black holes roaming our galaxy are born from rare, monstrous stars (less than one-thousandth of the galaxy’s stellar population) that are at least 20 times more massive than our Sun. These stars explode as supernovae, and the remnant core is crushed by gravity into a black hole. Because the self-detonation is not perfectly symmetrical, the black hole may get a kick, and go careening through our galaxy like a blasted cannonball.

Telescopes can’t photograph a wayward black hole because it doesn’t emit any light. However, a black hole warps space, which then deflects and amplifies starlight from anything that momentarily lines up exactly behind it.

Ground-based telescopes, which monitor the brightness of millions of stars in the rich star fields toward the central bulge of our Milky Way, look for such a tell-tale sudden brightening of one of them when a massive object passes between us and the star. Then Hubble follows up on the most interesting such events.

Kailash Sahu of the Space Telescope Science Institute in Baltimore, Maryland, along with his team, made the discovery in a survey designed to find just such isolated black holes. The warping of space due to the gravity of a foreground object passing in front of a star located far behind it will briefly bend and amplify the light of the background star as it passes in front of it. The phenomenon, called gravitational microlensing, is used to study stars and exoplanets in the approximately 20,000 events seen so far inside our galaxy.

The signature of a foreground black hole stands out as unique among other microlensing events. The very intense gravity of the black hole will stretch out the duration of the lensing event for over 200 days.

Next, Hubble was used to measure the amount of deflection of the background star’s image by the black hole. Hubble is capable of the extraordinary precision needed for such measurements. The star’s image was offset from where it normally would be by two milliarcseconds. That’s equivalent to measuring the diameter of a 25-cent coin in Los Angeles as seen from New York City.

This astrometric microlensing technique provided information on the mass, distance, and velocity of the black hole. The amount of deflection by the black hole’s intense warping of space allowed the team to estimate it weighs about seven solar masses. The isolated black hole is traveling across the galaxy at 90,000 miles per hour (fast enough to travel from Earth to the moon in less than three hours). That’s faster than most of the other neighboring stars in that region of our galaxy.

“Astrometric microlensing is conceptually simple but observationally very tough,” said Sahu. “It is the only technique for identifying isolated black holes.”

The existence of stellar-mass black holes has been known since the early 1970’s, but all of them–until now–are found in binary star systems.

“Detections of isolated black holes will provide new insights into the population of these objects in our Milky Way,” said Sahu.

NASA’s upcoming Nancy Grace Roman Space Telescope will discover several thousand microlensing events out of which many are expected to be black holes, and the deflections will be measured with very high accuracy.

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Upcoming International Seminar on Gravitational Waves!


Interested in how scientists collaborate across borders? Or how STEM projects are operated on an international scale?

Then check out the upcoming “Crossing Borders to Map Our Universe” seminar this March 21.

Anyone can join through Zoom here: https://psu.zoom.us/j/92182953190?pwd=d1Z6QmlReWQ5SUdWanJvWllDbDZ4UT09

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David Radice selected as a 2022 Sloan Fellow


The Sloan Foundation has announced that Dr. David Radice, assistant professor of physics and astronomy/astrophysics and member of the IGC, has been selected as a 2022 Sloan Fellow.

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Penn State is delighted to serve as a site for the 2023 Conference for Undergraduate Women in Physics.


Penn State is delighted to serve as a site for the 2023 Conference for Undergraduate Women in Physics. The organizational effort is led by IGC graduate student Unnati Akhouri, together with students Šárka Blahnik and Julian Mintz under the supervision of the local organizing commitee - Prof. Doug Cowen, Prof. Sarah Shandera, Prof. Miguel Mostafá, Prof. Louis Leblond and Prof. Kirstin Purdy-Drew. The effort is backed by the Department of Physics and the Institute for Gravitation and the Cosmos. The committee has also garnered local support from the Eberly College of Science, Department for Astronomy and Astrophysics, MRSEC, Centre for Excellence in Science Education and the student groups Physics and Astronomy for Women+, Society for Physics Students and Towards a More Inclusive Astronomy.

The conference will the held January 20-23, 2023 at Penn State. More information about registration and application deadlines will be out soon. We look forward to hosting many accomplished guest speakers and a fantastic cohort of undergraduate physicists!

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David Radice awarded 2022 Sloan Research Fellowship


David Radice, assistant professor of physics and of astronomy and astrophysics, has been honored with 2022 Alfred P. Sloan Research Fellowship in recognition of his research accomplishments. Awarded annually since 1955, the fellowship honors extraordinary researchers whose creativity, innovation, and research accomplishments make them stand out as the next generation of scientific leaders.

“Today’s Sloan Research Fellows represent the scientific leaders of tomorrow,” says Adam F. Falk, president of the Alfred P. Sloan Foundation. “As formidable young scholars, they are already shaping the research agenda within their respective fields—and their trailblazing won’t end here.”

Radice is one of 118 outstanding researchers from 51 institutions across the U.S. and Canada to make up this year’s cohort. The fellowships are awarded in close coordination with the scientific community. Candidates must be nominated by their fellow scientists and winners are selected by independent panels of senior scholars on the basis of a candidate’s research accomplishments, creativity, and potential. A Sloan Research Fellowship is one of the most prestigious awards available to young researchers.

Radice focuses his research on the study of explosive astrophysical events that produce gravitational waves and light, such as neutron-star mergers and core-collapse supernovae. His research makes use of large-scale supercomputing simulations. He is also interested in the development of new computational techniques and in the understanding of fundamental physics questions such as the nature of turbulence.

Radice’s honors and awards include an Early Career Research Program Award from the Department of Energy in 2020, a Giulio Rampa Thesis Prize from the University of Pavia in 2014, and a Prize Postdoctoral Fellowship from the California Institute of Technology in 2013.

Prior to joining the faculty at Penn State, Radice was an associate research scholar at Princeton University and at the Institute for Advanced Study from 2016 to 2019 and a Walter Burke Fellow in Theoretical Astrophysics and Relativity at the California Institute of Technology from 2013 to 2016. He earned a doctoral degree in gravitational wave astronomy at the Max Planck Institute for Gravitational Physics, Germany, in 2013 and master’s and bachelor’s degrees in mathematical engineering at Politecnico di Milanoin Italy in 2009 and 2006, respectively.

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A Resounding Endorsement for Cosmic Explorer Gravitational Wave Observatory from the Astro2020 Decadal Survey


IGC member B.S. Sathyaprakash was a co-chair of the Science Team of the Gravitational Wave International Committee, charged to develop a vision for the next generation of ground-based gravitational wave detectors.

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Quasars, black holes, and a cosmological conundrum: A quest for the origin of the most-distant quasars in the early universe


Astrophysicist Yuexing Li’s quest began with quasars, luminous galaxies powered by supermassive black holes actively devouring matter and releasing enormous amounts of electromagnetic radiation so hot and bright we can see it more than 13 billion light years away.

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Stephanie Wissel has been selected for the Downsbrough Early Career Professor in Physics!


We are delighted to announce that Dr. Stephanie Wissel, assistant professor of physics and astronomy/astrophysics, has been selected for the Downsbrough Early Career Professor in Physics! Stephanie works in experimental astro-particle physics with expertise in the detection and study of cosmic neutrinos. She’s pursuing the discovery of cosmogenic and astrophysical neutrinos at ultra-high energies (greater than 100 PeV) using radio detection techniques. These experiments will provide unprecedented insight into Nature’s highest energy accelerators and into the physics of extreme environments such as pulsars, gamma-ray bursts, and active galactic nuclei. Stephanie also plays a key role in our department’s educational, service, and outreach missions, including taking leadership in our efforts to build an inclusive, diverse community of graduate students and postdocs. Please join us in congratulating Stephanie on this well-deserved honor!