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APOD: A Meteor and the Gegenschein
Is the night sky darkest in the direction opposite the Sun? No. In fact, a rarely discernable faint glow known as the gegenschein (German for "counter glow") can be seen 180 degrees around from the Sun in an extremely dark sky. The gegenschein is sunlight back-scattered off small interplanetary dust particles. These dust particles are millimeter sized splinters from asteroids and orbit in the ecliptic plane of the planets. Pictured here from last March is one of the more spectacular pictures of the gegenschein yet taken. The deep exposure of an extremely dark sky over Teide Observatory in Spain's Canary Islands shows the gegenschein as part of extended zodiacal light. Notable background objects include a bright meteor (on the left), the Big Dipper (top right), and Polaris (far right). The meteor nearly points toward Mount Teide, Spain's highest mountain, while the Pyramid solar laboratory is visible on the right. During the day, a phenomenon like the gegenschein called the glory can be seen in reflecting air or clouds opposite the Sun from an airplane.
Weather at the Eyring Science Center
Check current conditions and historical weather data at the ESC.
BYU Physics & Astronomy During the COVID-19 Pandemic by Brian Anderson
How are things different for BYU Physics & Astronomy during the pandemic?
See the Stars Even Better at the ESC Observatory
New state-of-the-art 23 inch telescope making access to the night sky a dream come true
New Mill Becomes Part of the P&A Family
New self-enclosed mill to enhance machining capabilities
Catching up on Five Years
Thanking our retireed colleagues and welcoming new ones

Selected Publications

How much do cryogenic & low-oxygen environments slow aluminum oxidation
BYU Authors: S. Merlin Hart, Donovan K. Smith, and David D. Allred, published in Proc. SPIE

Aluminum is the best choice of material for broadband mirrors. However, once an oxide layer forms on the surface of the mirrors the reflectance in the far ultraviolet range decreases. The study of Al mirrors is difficult because they oxidize so quickly in the air. This makes reproducibility and joint work between laboratories difficult because the mirrors will oxidize and make successive measurements inaccurate. We have found that storing aluminum thin-film mirrors in low oxygen environments (such as liquid nitrogen, dry ice, and hexane) retards mirror oxidation. We examined the retardation of the growth of aluminum oxide during storage in these environments. This oxidation retardation was most pronounced when mirrors were stored in liquid nitrogen. In comparing the growth rate of oxide out of storage to that while it was in storage, we found that the apparent growth of aluminum oxide, is 1/500 in liquid nitrogen, 1/200 in hexane and 1/40 in dry ice.

Sound power of vibrating cylinders using the radiation resistance matrix and a laser vibrometer
BYU Authors: Caleb B. Goates, Cameron B. Jones, Scott D. Sommerfeldt, and Jonathan D. Blotter, published in J. Acoust. Soc. Am.

Research has shown that using acoustic radiation modes combined with surface velocity measurements provide an accurate method of measuring the radiated sound power from vibrating plates. This paper investigates the extension of this method to acoustically radiating cylindrical structures. The mathematical formulations of the radiation resistance matrix and the accompanying acoustic radiation modes of a baffled cylinder are developed. Computational sound power calculations using the vibration-based radiation mode (VBRM) method and the boundary element method are then compared and shown to have good agreement. Experimental surface velocity measurements of a cylinder are taken using a scanning laser Doppler vibrometer and the VBRM method is used to calculate sound power. The results are compared to sound power measurements taken using ISO 3741.

Architectures of Exoplanetary Systems. II. An Increase in Inner Planetary System Occurrence toward Later Spectral Types for Kepler's FGK Dwarfs
BYU Authors: Darin Ragozzine, published in Astron. J.

The Kepler mission observed thousands of transiting exoplanet candidates around hundreds of thousands of FGK dwarf stars. He et al. applied forward modeling to infer the distribution of intrinsic architectures of planetary systems, developed a clustered Poisson point process model for exoplanetary systems (SysSim) to reproduce the marginal distributions of the observed Kepler population, and they showed that orbital periods and planet radii are clustered within a given planetary system. Here, we extend the clustered model to explore correlations between planetary systems and their host-star properties. We split the sample of Kepler FGK dwarfs into two halves and model the fraction of stars with planets (0.5–10R⊕ and 3–300 days), fswpa, as a linear function of the Gaia DR2 color. We confirm previous findings that the occurrence of these planetary systems rises significantly toward later-type (redder) stars. The fraction of stars with planets increases from  for F2V dwarfs to  for mid-K dwarfs. About half () of all solar-type (G2V) dwarfs harbor a planetary system between 3 and 300 days. This simple model can closely match the observed multiplicity distributions of both the bluer and redder halves in our sample, suggesting that the architectures of planetary systems around stars of different spectral types may be similar aside from a shift in the overall fraction of planet-hosting stars.