Category: Research

Alex McDaniel is a postdoctoral fellow in the Clemson University’s Department of Physics and Astronomy and his collaborators search dwarf galaxies for dark matter “that self-annihilates into ordinary matter and gamma rays, a form of light at the highest energy levels. Dwarf galaxies are ideal for study because they are small, rich in dark matter and mostly lack other astrophysics phenomena such as gas, dust and supernova that could contaminate the findings.” McDaniel explains that they specifically look for these because they can give a clear signal or can help rule out certain particle theories. 

Read more here: 
Clemson astrophysicist’s research could provide a hint in the search for dark matter | Clemson News

Dieter Hartmann and an international team of astronomers “obtained observational evidence for the creation of rare heavy elements in the aftermath of a cataclysmic explosion triggered by the merger of two neutron stars.” They were studying a massive gamma-ray burst named GRB230307A, which was first detected on March 7, 2023. Scientists discovered that this burst resulted from two neutron stars merging in a distant galaxy. 

“The breakthrough discovery puts astronomers one step closer to solving the mystery of the origin of elements that are heavier than iron.”

Adapted from:
Astronomers discover heavy elements after bright gamma-ray burst from neutron star merger | Clemson News

Apparao Rao, Clemson University and Bingan Lu, Hunan University

“In a newly published study, we describe our design for a self-extinguishing rechargeable battery. It replaces the most commonly used electrolyte, which is highly combustible – a medium composed of a lithium salt and an organic solvent – with materials found in a commercial fire extinguisher.

An electrolyte allows lithium ions that carry an electric charge to move across a separator between the positive and negative terminals of a lithium-ion battery. By modifying affordable commercial coolants to function as battery electrolytes, we were able to produce a battery that puts out its own fire.”

Read more here: 
Self-extinguishing batteries could reduce the risk of deadly and costly battery fires | Clemson News

On April 14, 2023, five Physics & Astronomy graduate students and one CU-ICAR graduate student conducting research at the Clemson Nanomaterials Institute (CNI) presented six papers at the annual SC EPSCoR conference in Summerville, SC. Basanta Ghimire, Evan Watkins, Nawraj Sapkota, Peshal Karki, and Janak Basel each presented their work at this year’s conference. In addition to the student presentations, Research Assistant Professor, Sriparna Bhattacharya also chaired one of the conference sessions.

The SC EPSCoR Program, joined by SC NASA EPSCoR, invited faculty, post-doctoral fellows, graduate students, undergraduate students, and STEM professionals to this year’s state conference. Conference presentations built on the themes of the last five years, promoting collaboration among South Carolina colleges and universities.

German radio journalist Kristian Thees and German actress and entertainer Anke Engelke, talk about the NASA sounding rocket experiment INCAA and the image of tracer releases in Alaska submitted by listener Prof. Gerald Lehmacher, who was co-investigator for the experiment. Prof. Steve Kaeppler and Prof. Miguel Larsen were principal investigator and co-investigator, respectively. The photo taken by Danute Paukstys from Wasilla, Alaska is featured in the podcast’s blog and discussed (in German) in the episode of May 26, 2022 (starting at about 8:50 min). Two sounding rockets were successfully launched on April 7, 2022 from Poker Flat, Alaska to study ion-neutral coupling under active aurora. The payloads carried experiments from the University of California Berkeley, the University of Calgary and Clemson University.

Supermassive black holes are the universe’s most immense single objects. These monsters can weigh more than a billion suns, and are the subjects of intense interest in the astronomical community. They are the engines powering the spectacular jets of material (so-called AGN jets) that emanate from the cores of some galaxies, and they offer precious clues about the growth of cosmic structure. One very famous supermassive black hole — lurking at the center of the galaxy M87, more than 50 million light years from Earth — made headlines last year when the Event Horizon Telescope (the name given to a global network of radio telescopes) made it the first black hole to be imaged directly.

These black holes were probably born in the early universe, left behind following the explosive deaths of first-generation stars. But how did they grow from seedlings (only 10 – 100 times the mass of the sun) into the giants they are today? This question is something astronomers have been trying to answer for decades. Most will agree that some of their growth is due to consuming the gas and debris from their host galaxies, but will concede this cannot be the entire story — there is a well-known maximum rate (called the Eddington limit) at which a black hole can accrete gas, and many black holes are simply too massive to have grown by accretion alone since the beginning of the universe. These black holes have likely grown faster by merging with partners: falling into orbit around one another, and eventually coalescing after after a long, inward spiraling dance. The details of this process are still murky — why, and how often do supermassive black hole mergers take place? And crucially, where are the supermassive black hole binaries, dancing toward coalescence?

Currently the best supermassive black hole binary candidate is a system known as OJ-287. This system exhibits regular outbursts (twice every 12 years), which can be explained if the smaller of the two black holes has a highly inclined and eccentric orbit, punching through and lighting up the larger one’s accretion disk (its meal of swirling debris) twice each orbit. These two objects are fatefully bound. On each orbit they get closer together, converting their orbital kinetic energy into gravitational wave radiation. In roughly 10,000 years from now, they will collide and merge together, producing a powerful burst of gravitational wave (GW) emission. Merger events like this would be detected by a space-based interferometric GW detector, such as the proposed LISA mission.

If OJ-287 is indeed a binary black hole, it would be proof that supermassive black holes do merge. But it raises a new question: how did these objects become bound to one another in first place? Such pairs might have been introduced when their respective host galaxies merged together. They could then have “sunk” to the center and become gravitationally bound when separated by 100’s to 1000’s of light-years. This is where things get tricky: when they are so widely separated, the orbit is barely affected by GW radiation. But the binary in OJ-287 has somehow shrunk to less than 0.1 light-year separation, close enough for GW’s to drive it to coalesce. The question of how a binary black hole’s separation can shrink to sub-light-year scales is so critical that it’s acquired a special name: “the final parsec problem.”

The solution to the final parsec problem is likely connected to a critical fact — black holes do not exist in a vacuum. The density of interstellar gas is small, on average one proton per cubic centimeter, but its effect on binary black holes over the course of billions of years can be critical. The black holes’ gravity pulls gas into a disk that swirls around the binary — a so-called circumbinary disk, or CBD. The dynamics of the binary and its CBD are complex, and beautiful: the circling black holes induce tidal interactions that push and pull gas in the CBD, causing some of it to fall inwards along narrow streams, and gather into smaller so-called minidisks which then accrete onto their respective black holes. The gas, in turn, exerts a gravitational pull on the binary, which might ultimately drive the black holes to spiral inwards… but it also might drive them apart!

To determine the effect of gas on the evolution of binary black holes, we need to unravel the complex dynamics of gas orbiting two black holes. This type of nonlinear physics problem can only be tackled with the aid of large-scale computer simulations, which solve the equations of gas dynamics and gravitation together, and at a very high level of detail.

Dr. Jian He of the Department of Physics & Astronomy Clemson is a corresponding author of a Science article describing a new van der Waals inorganic semiconductor. The van der Waals inorganic semiconductors are generally brittle and prone to cleavage in its bulk form at room temperature. However, an international team of scientists found that this is not always the case. In a recent article entitled “Exceptional plasticity in the bulk single-crystalline van der Waals semiconductor InSe” published in Science , the authors show that bulk single crystalline InSe can be morphed into simple origami, Mobius ring, engineeringly strained to 80% in compression, > 10% in tensile and bending strain along specific direction, without losing the structural integrity. The peculiar long-range Coulomb interaction across the van der Waals gap plays a key role in the observed bulk superplastic deformability. The scientific and technical implications of this discovery include flexible and plastic electronics, sensors, and energy harvesting devices.  A perspective article, “Ductile van der Waals materials”, was published in the same journal issue to highlight this discovery.

Graduate student Komal Kumari has been elected student representative to the NSF CEDAR Science Steering Committee where she will serve a two year term. The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) Program, funded by the National Science Foundation’s Atmospheric and Geospace Sciences Division, studies the interaction region of the Earth’s tenuous upper atmosphere. For over 25 years, CEDAR brings together the U.S. aeronomy community to combine observations from ground based and space based platforms, theory and modeling. As student rep, Komal will provide graduate student input to the CEDAR programmatic priorities and organize the one day student workshop that is part of the annual CEDAR conference. Please join me in congratulating Komal on this well deserved honor.

Bishwambhar Sengupta, a PhD student with Prof. Takacs, has just accepted an offer for a post-doctoral position at the University of Washington in Seattle. He will join the group of Eric Floyd in the department of Radiation Oncology. Let’s congratulate Bishwambhar on this next excellent next step in his career.