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Thumbnail of Chamaeleon Dark Nebulas
Sometimes the dark dust of interstellar space has an angular elegance. Such is the case toward the far-south constellation of Chamaeleon. Normally too faint to see, dark dust is best known for blocking visible light from stars and galaxies behind it. In this 11.4-hour exposure, however, the dust is seen mostly in light of its own, with its strong red and near-infrared colors creating a brown hue. Contrastingly blue, a bright star Beta Chamaeleontis is visible on the upper right of the V, with the dust that surrounds it preferentially reflecting blue light from its primarily blue-white color. All of the pictured stars and dust occur in our own Milky Way Galaxy with one notable exception: a white spot just below Beta Chamaeleontis is the galaxy IC 3104, which lies far in the distance. Interstellar dust is mostly created in the cool atmospheres of giant stars and dispersed into space by stellar light, stellar winds, and stellar explosions such as supernovas.
Mount Timpanogos with sky above
Temp:  46 °FN2 Boiling:75.9 K
Humidity: 71%H2O Boiling:   368.4 K
Pressure:85 kPaSunrise:7:18 AM
Wind:1 m/s   Sunset:5:06 PM
Precip:0 mm   Sunlight:0 W/m²  
Image for New Applied Physics Major with an Emphasis in Data Science
Starting Fall 2025, BYU will offer a new Applied Physics: Data Science major that combines rigorous physics training with data science skills to prepare students for the growing demand in data-driven careers.
Image for The Physics of Life
BYU's new Biological Physics course introduces students to the physics behind biological processes, fostering interdisciplinary skills to tackle complex biological questions.
Image for Dr. Kent Gee Receives Top faculty Award
Dr. Kent Gee has been named the recipient of the Karl G. Maeser Distinguished Faculty Lecturer Award
Image for Drs. Davis and Vanfleet Receive Technology Transfer Award
BYU Physics and Astronomy Professors Dr. Davis and Dr. Vanfleet recently received the 2024 award for outstanding achievement in technology transfer from the BYU Technology Transfer Office.

Selected Publications

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Sabrina Hatt and Benjamin M. Frandsen (et al.)

Altermagnets represent a new class of magnetic phases without net magnetization, invariant under a combination of rotation and time reversal. Unlike conventional collinear antiferromagnets (AFM), altermagnets could lead to new correlated states and important material properties deriving from their nonrelativistic spin-split band structure. Indeed, they serve as the magnetic analogue of unconventional superconductors and can yield spin-polarized electrical currents in the absence of external magnetic fields, making them promising candidates for next-generation spintronics. Here, we report altermagnetism in the correlated insulator, magnetically ordered tetragonal oxychalcogenide, La2O3Mn2Se2. Symmetry analysis reveals a 𝑑𝑥2−𝑦2-wave-like spin-momentum locking arising from the Mn2O Lieb lattice, supported by density functional theory (DFT) calculations. Magnetic measurements confirm the AFM transition below ∼166K while neutron pair distribution function analysis reveals a 2D short-range magnetic order that persists above the Néel temperature. Single crystals are grown and characterized using x-ray diffraction, optical and electron microscopy, and micro-Raman spectroscopy to confirm the crystal structure, stoichiometry, and uniformity. Our findings establish La2O3Mn2Se2as a model altermagnetic system realized on a Lieb lattice.

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Mark C. Anderson and Kent L. Gee

When the SpaceX Falcon-9 rocket booster descends through the atmosphere after a launch, it produces a sonic boom with three shocks in the far field, rather than the usual two-shock N-wave. In this Letter, the additional shock's origin is explained using sonic boom theory, nonlinear propagation modeling, computational fluid dynamics, and photographic evidence. The extra central shock results from a forward-migrating compression wave caused by the grid fins merging with a rearward-migrating rarefaction wave caused by the lower portions of the booster, including the folded landing legs.

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Group-theoretical and linear-algebraic methods and tools have recently been developed that aim to exhaustively identify the small-angle rotational rigid-unit modes (RUMs) of a given framework material. But in their current form, they fail to detect RUMs that require a compensating lattice strain which grows linearly with the amplitude of the rigid-unit rotations. Here, we present a systematic approach to including linear strain compensation within the linear-algebraic RUM-search method, so that any geometrically possible small-angle RUM can be detected.

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Grant W. Hart, Kent L. Gee, Eric G. Hintz, Nathan F. Carlston, and Giovanna G. Nuccitelli (et al.)

At 7:30 AM on October 6, 2020 Space-X launched a Falcon-9 rocket from Kennedy Space Center. Photographer Trevor Mahlmann had positioned his camera in the location where the rocket would pass in front of the rising sun and took a series of images of that encounter. The high-intensity sound and shock waves originating in the plume are imaged by passing in front of the sun, particularly near the edge of the sun. This can be considered as a type of schlieren imaging system. The sound emitted from a supersonic rocket plume is thought to be due to Mach wave radiation. The images were processed to enhance the visibility of the propagating shock waves, and the propagation of those shock waves was traced back to the plume. This allowed the source location and emission direction of the sound to be determined. The measured shocks were found to be consistent with the predictions of Mach wave radiation from the plume, originating about 15-20 nozzle diameters down the plume, and radiating in a wide lobe peaking at about 70° from the plume direction. There are also indications that lower frequency waves are preferentially emitted at smaller angles relative to the plume.

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Tyce W. Olaveson, Kent L. Gee, Logan T. Mathews, and Hunter J. Pratt (et al.)

This paper presents a comprehensive overview of the operation and spectral performance of a novel lab-scale afterburning jet noise rig at Virginia Tech. The study involved steady-state operation at relevant Total Temperature Ratios (TTR) of approximately 6, typical for afterburning jets. The flow was discharged through a scaled-down GE F-404 supersonic nozzle, and far-field noise measurements were acquired using ground microphones positioned at 27 angular locations on a concrete pad. A key focus of the study is to benchmark the rig's performance by comparing its far-field Overall Sound Pressure Level (OASPL) with that of T-7A and F-35B aircraft operating at afterburner power. The investigation revealed that Nozzle Pressure Ratio (NPR) exerts a significant influence on OASPL at relatively close TTRs. Furthermore, the effects of varying TTR and NPR on OASPL were compared with trends observed in F-35A and F-35B operating at two distinct afterburner power levels. Acoustic efficiency in the presented cases lies in the range 0.41% to 0.51%. Phenomena only observed in full scale afterburning jet engine tests were reproduced for the first time in a laboratory scaled rig. This allowed the identification that engine combustion instabilities can convect downstream through the nozzle and impact the far-field noise spectrum. These instabilities manifest as distinct 'instability streaks' in a spatio-spectral map. The present study highlights the importance of conducting high TTR jet noise experiments in a controlled environment with known operating parameters (total pressure, total temperature, mass flow rate, dynamic pressure, etc.) to enhance the understanding of afterburning jet noise phenomena.

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Kent L. Gee, Noah L. Pulsipher, Makayle S. Kellison, Grant W. Hart, Logan T. Mathews, and Mark C. Anderson

his Letter analyzes launch noise from Starship Super Heavy's Flights 5 and 6. While Flight-5 data covered 9.7-35.5 km, the stations during Flight 6 spanned 1.0-35.5 km. A comparison of A-weighted and unweighted maximum and exposure levels is made between flights and with an updated environmental assessment (EA). Key findings include: (a) the two flights' noise levels diverge beyond 10 km, (b) EA models overestimate A-weighted metrics, and (c) the acoustic energy from a Starship launch is equivalent to 2.2 Space Launch System launches or ∼11 Falcon 9 launches. These measurements help predict Starship's noise levels around Kennedy Space Center.