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How do stars form? Most form in giant molecular clouds located in the central disk of a galaxy. The process is started, influenced, and limited by the stellar winds, jets, high energy starlight, and supernova explosions of previously existing stars. The featured video shows these complex interactions as computed by the STARFORGE simulation of a gas cloud 20,000 times the mass of our Sun. In the time-lapse visualization, lighter regions indicate denser gas, color encodes the gas speed (purple is slow, orange is fast), while dots indicate the positions of newly formed stars. As the video begins, a gas cloud spanning about 50 light years begins to condense under its own gravity. Within 2 million years, the first stars form, while newly formed massive stars are seen to expel impressive jets. The simulation is frozen after 4.3 million years, and the volume then rotated to gain a three-dimensional perspective. Much remains unknown about star formation, including the effect of the jets in limiting the masses of subsequently formed stars. Portal Universe: Random APOD Generator
Check current conditions and historical weather data at the ESC.
Transtrum received a BYU Early Career Scholarship Award.
Eric Hirschman received an Outstanding Service Award from the College of Physical and Mathematical Sciences.

Selected Publications

BYU Authors: J W Moody and M Joner, published in Mon. Not. Roy. Astron. Soc.

We report a characterization of the multiband flux variability and correlations of the nearby (z = 0.031) blazar Markarian 421 (Mrk 421) using data from Metsähovi, Swift, Fermi-LAT, MAGIC, FACT, and other collaborations and instruments from 2014 November till 2016 June. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F>1 TeV < 1.7 × 10−12 ph cm−2 s−1) and in the 2–10 keV (X-ray) band (F2−10keV<3.6×10−112−10keV<3.6×10−11 erg cm−2 s−1), during which the Swift-BAT data suggest an additional spectral component beyond the regular synchrotron emission. The highest flux variability occurs in X-rays and very high-energy (E > 0.1 TeV) γ-rays, which, despite the low activity, show a significant positive correlation with no time lag. The HRkeV and HRTeV show the harder-when-brighter trend observed in many blazars, but the trend flattens at the highest fluxes, which suggests a change in the processes dominating the blazar variability. Enlarging our data set with data from years 2007 to 2014, we measured a positive correlation between the optical and the GeV emission over a range of about 60 d centred at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 d centred at a time lag of 43+9−643−6+9 d. This observation is consistent with the radio-bright zone being located about 0.2 parsec downstream from the optical/GeV emission regions of the jet. The flux distributions are better described with a lognormal function in most of the energy bands probed, indicating that the variability in Mrk 421 is likely produced by a multiplicative process.

BYU Authors: Scott D. Bergeson, published in Phys. Plasmas

Charged particle transport plays a critical role in the evolution of high energy-density plasmas. As high-fidelity plasma models continue to incorporate new micro-physics, understanding multi-species plasma transport becomes increasingly important. We briefly outline theoretical challenges of going beyond single-component systems and binary mixtures as well as emphasize the roles experiment, simulation, theory, and modeling can play in advancing this field. The 2020 Division of Plasma Physics mini-conference on transport in Transport in Non-Ideal, Multi-Species Plasmas was organized to bring together a broad community focused on modeling plasmas with many species. This special topics issue of Physics of Plasmas touches on aspects of ion transport presented at that mini-conference. This special topics issue will provide some context for future growth in this field.

BYU Authors: Benjamin A. Frandsen, Charlotte Read, Jade Stevens, Colby Walker, Mason Christiansen, Roger G. Harrison, and Karine Chesnel, published in Phys. Rev. Materials

The magnetic properties of Fe3O4 nanoparticle assemblies have been investigated in detail through a combination of vibrating sample magnetometry (VSM) and muon spin relaxation (μSR) techniques. Two samples with average particle sizes of 5 and 20 nm, respectively, were studied. For both samples, the VSM and μSR results exhibit clear signatures of superparamagnetism at high temperature and magnetic blocking at low temperature. The μSR data demonstrate that the transition from the superparamagnetic to the blocked state occurs gradually throughout the sample volume over an extended temperature range due to the finite particle size distribution of each nanoparticle batch. The transition occurs between approximately 3 and 45 K for the 5-nm nanoparticles and 150 and 300 K for the 20-nm nanoparticles. The VSM and μSR data are further analyzed to yield estimates of microscopic magnetic parameters including the nanoparticle spin-flip activation energy EA, magnetic anisotropy K, and intrinsic nanoparticle spin reversal attempt time τ0. These results highlight the complementary information about magnetic nanoparticles that can be obtained by bulk magnetic probes such as magnetometry and local magnetic probes such as μSR.