Utah Aurora - May 10/11 2024

BYU Astronomy Research Group Joins the Astrophysical Research Consortium (ARC)

As of January 2021 BYU will be a member of the ARC Consortium (Link to Consortium) with access to the ARC 3.5-m telescope and the 0.5-m ARCSAT telescope.  The primary use of the ARC 3.5-m telescope time is for graduate student projects.  This provides a wide array of instrumentation that is currently being used to study objects in the solar system all the way to studies of the large scale structure of the Universe.

Other BYU Astronomy Facilities

In addition to our telescope time from the ARC consortium, we operate a number of our own astronomical facilities

West Mountain Observatory (West Mountain)

This is our mountain observatory at about 6600 ft above sea level.  This consists of three telescopes: 0.9-m, 0.5-m, and a 0.32-m. It is a 40 minute drive that ends in a 5 miles drive up a dirt road. The mountain itself can be seen from campus. We don't provide any tours of this facility.

Orson Pratt Observatory

The Orson Pratt Observatory is named for an early apostle of the Church of Jesus Christ of Latter-Day Saints.  It is our campus telescope facility and contains a wide variety of telescopes for student research and public outreach. We operate a 24" PlaneWave telescope in the main campus dome, plus a 16", two 12", one 8", and a 6" telescope on our observation deck.  The telescopes are all fully robotic. Beyond this we have a large sections of telescopes used on public nights.

Royden G. Derrick Planetarium (Planetarium)

This is a 119 seat, 39" dome planetarium with acoustically treated walls to allow it's use as a lecture room. Recently we upgraded to an E&S Digistar7 operating system with 4K projectors.  The planetarium is used for teaching classes, public outreach, and astronomy education research projects.





Selected Publications

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L-band photometry of L and T dwarfs
We present K- and L-band photometry obtained with the Keck I telescope for a representative sample of L and T dwarfs. These observations were motivated in part by the dominant role H(2)O and CH(4) play in shaping the flux near 2 and 3 mum and by the potential use of these bands as indicators of spectral class in the infrared. In addition, these observations aid the determination of the bolometric luminosity of L and T dwarfs. Here we report the K, L', and L(s) magnitudes of our objects and the trends observed in the (K-L') and (K-L(s)) colors as a function of L and T dwarf spectral class. We compare these colors with theoretical models, derive a relationship between effective temperature and L spectral class, and compare our temperature estimates with others.
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L-Band Photometry and Spectroscopy of L and T Dwarfs: Exploring Infrared Spectral Typing
The classification of L and T dwarfs requires the identification of easily observed quantities such as colour ratios or strengths of spectral features. Although current classification schemes based on optical spectroscopy for L dwarfs do exist, it is important to classify L and T dwarfs using other wavelengths as well. Observations of L and T dwarfs at infrared wavelengths are sensitive to physical processes controlling the atmospheres and temperatures of brown dwarfs which provide for the possibility of L and T dwarf classification using infrared observations. Here we present the first results of our observing program using the Keck telescope to obtain infrared photometry and spectroscopy of L and T dwarfs.
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Narrow Band Near Infrared Photometry of Brown Dwarfs
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Reflected Spectra and Albedos of Extrasolar Giant Planets. I. Clear and Cloudy Atmospheres

The reflected spectra of extrasolar giant planets are primarily influenced by Rayleigh scattering, molecular absorption, and atmospheric condensates. We present model geometric albedo and phase-integral spectra and Bond albedos for planets and brown dwarfs with masses between 0.8 and 70 Jupiter masses. Rayleigh scattering predominates in the blue while molecular absorption removes most red and infrared photons. Thus cloud-free atmospheres, found on giant planets with effective temperatures exceeding about 400 K, are quite dark in reflected light beyond 0.6 μm. In cooler atmospheres, first water clouds and then other condensates provide a bright reflecting layer. Only planets with cloudy atmospheres will be detectable in reflected light beyond 1 μm. Thermal emission dominates the near-infrared for warm objects with clear atmospheres. However the presence of other condensates, not considered here, may brighten some planets in reflected near-infrared light and darken them in the blue and UV. Bond albedos, the ratio of the total reflected to incident power, are sensitive to the spectral type of the primary. Most incident photons from early-type stars will be Rayleigh scattered, while most incident photons from late-type stars will be absorbed. The Bond albedo of a given planet thus may range from 0.4 to 0.05, depending on the primary type. Condensation of a water cloud may increase the Bond albedo of a planet by up to a factor of 2. The spectra of cloudy planets are strongly influenced by poorly constrained cloud microphysical properties, particularly particle size and supersaturation. Both Bond and geometric albedos are comparatively less sensitive to variations in planet mass and effective temperature.

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Model bond albedos of extrasolar giant planets
D. Stephens (et al.)
The atmospheres of extrasolar giant planets are modeled with various effective temperatures and gravities, with and without clouds. Bond albedos are computed by calculating the ratio of the flux reflected by a planet (integrated over wavelength) to the total stellar flux incident on the planet. This quantity is useful for estimating the effective temperature and evolution of a planet. We find it is sensitive to the stellar type of the primary. For a 5 M-Jup planet the Bond albedo varies from 0.4 to 0.3 to 0.06 as the primary star varies from A5V to G2V to M2V in spectral type. It is relatively insensitive to the effective temperature and gravity for cloud-free planets. Water clouds increase the reflectivity of the planet in the red, which increases the Bond albedo. The Bond albedo increases by an order of magnitude for a 13 M-Jup planet with an M2V primary when eater clouds are present. Silicate clouds, on the other hand, can either increase or decrease the Bond albedo, depending on whether there are many small grains (the former) or few large grains (the latter). (C) 1999 Elsevier Science Ltd. All rights reserved.
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The effect of clouds on the visible spectra of extrasolar giant planets