BYU Represents at DPS

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

Thumbnail of figure from publication
3.6-7.9 mu m photometry of L and T dwarfs and the prevalence of vertical mixing in their atmospheres
By D. Stephens (et al.)
Abstract: We present new L' (3.75 mu m) photometry of six L and T dwarfs, and M' (4.70 mu m) photometry of 10 L and T dwarfs, observed at the Gemini (North) Observatory, and new 3.55, 4.49, 5.73, and 7.87 mu m photometry of nine L and T dwarfs, obtained with the Spitzer Space Telescope. The sample includes unusually blue and red dwarfs selected from our near infrared studies. The data are combined with previously published L', M', and Spitzer photometry of L and T dwarfs, and trends of colors with spectral type and other colors are examined. Recent model atmospheres by Marley and Saumon are used to generate synthetic colors for ranges of effective temperature, gravity, grain sedimentation efficiency, metallicity, and vertical mixing efficiency. We explore how these parameters affect the mid-infrared colors of L and T dwarfs and find that the data are modeled satisfactorily only if substantial vertical mixing occurs in both L and T dwarf atmospheres. The location and range of the L and T dwarf sequences in IRAC color-color and color- magnitude diagrams is also only reproduced if this mixing occurs, with a range of efficiency described by K-zz similar to 10(2)-10(6) cm(2) s(-1). The colors of the unusually red dwarfs are best reproduced by nonequilibrium models with low sedimentation efficiency, i.e., thick cloud decks, and the colors of the unusually blue dwarfs by nonequilibrium models with high sedimentation efficiency, i.e., thin cloud decks. The K-L' and Spitzer [3:55] - [4:49] colors can be used as indicators of effective temperature for L and T dwarfs, but care must be taken to include gravity and metallicity effects for late-T dwarfs and vertical mixing for both late-L and T dwarfs.
Thumbnail of figure from publication
Discovery of a binary Centaur
By Denise C. Stephens (et al.)
Abstract: We have identified a binary companion to (42355) 2002 CR46 in our ongoing deep survey using the Hubble Space Telescope's High Resolution Camera. It is the first companion to be found around an object in a non-resonant orbit that crosses the orbits of giant planets. Objects in orbits of this kind, the Centaurs, have experienced repeated strong scattering with one or more giant planets and therefore the survival of binaries in this transient population has been in question. Monte Carlo simulations suggest, however, that binaries in (42355) 2002 CR46-like heliocentric orbits have a high probability of survival for reasonable estimates of the binary's still-unknown system mass and separation. Because Centaurs are thought to be precursors to short period comets, the question of the existence of binary comets naturally arises; none has yet been definitively identified. The discovery of one binary in a sample of eight observed by HST suggests that binaries in this population may not be uncommon. (c) 2006 Elsevier Inc. All rights reserved.
Thumbnail of figure from publication
Evidence of orbital motion in the binary brown dwarf Kelu-1AB
By D. C. Stephens (et al.)
Abstract: We have resolved Kelu-1 into a binary system with a separation of similar to 290 mas using the Laser Guide Star Adaptive Optics system on the Keck II telescope. We have also reanalyzed a 1998 HST observation of Kelu-1 and find that the observed PSF is best fit by a binary object separated by 45 mas. Observations at multiple epochs confirm that the two objects share a common proper motion and clearly demonstrate the first evidence of orbital motion. Kelu-1B is fainter than Kelu-1A by 0.39 +/- 0.01 mag in the K' filter and 0.50 +/- 0.01 mag in the H filter. We derive spectral types of L2 +/- 1 and L3.5 +/- 1 for Kelu-1A and B, respectively. The separation of flux into the two components rectifies Kelu-1's overluminosity problem, which has been known for quite some time. Given the available data, we are able to constrain the inclination of the system to >81 degrees and the orbital period to greater than or similar to 40 yr.
Thumbnail of figure from publication
Detection of six trans-neptunian binaries with nicmos: A high fraction of binaries in the cold classical disk
By D. C. Stephens (et al.)
Abstract: We have analyzed a homogeneous set of observations of 81 trans-Neptunian objects obtained with NIC2 on the Hubble Space Telescope with the goal of identifying partially resolved binaries. Using PSF fitting we have identified six likely binaries in addition to the three new binaries already found in this data set. We find that 11(-2)(+5)% of trans-Neptunian objects are binaries at the separation and brightness limits of NIC2. The identification of these new binaries significantly increases the known lower limit to the binary fraction among trans-Neptunian objects. The origin of such a high fraction of binaries remains to be determined. Most interestingly, detectable binaries appear to be about 4 times more common among the cold classical disk than in the dynamically excited populations.
Thumbnail of figure from publication
Diverse albedos of small trans-neptunian objects
By D. C. Stephens (et al.)
Abstract: Discovery of trans-neptunian object (TNO) satellites and determination of their orbits has recently enabled estimation of the size and albedo of several small TNOs, extending the size range of objects having known size and albedo down into the sub-100 km range. In this paper we compute albedo and size estimates or limits for 20 TNOs, using a consistent method for all binary objects and a consistent method for all objects having reported thermal fluxes. As is true for larger TNOs, the small objects show a remarkable diversity of albedos. Although the sample is limited, there do not yet appear to be any trends relating albedo to other observable properties or to dynamical class, with the possible exception of inclination. The observed albedo diversity of TNOs has important implications for computing the size-frequency distribution, the mass, and other global properties of the Kuiper belt derived from observations of objects' apparent magnitudes and may also point the way toward an improved compositional taxonomy based on albedo in addition to color. (c) 2005 Elsevier Inc. All rights reserved.
Thumbnail of figure from publication
The orbit, mass, and albedo of transneptunian binary (66652) 1999 RZ(253)
By D. C. Stephens (et al.)
Abstract: We have observed (66652) 1999 RZ(253) with the Hubble Space Telescope at seven separate epochs and have fit an orbit to the observed relative positions of this binary. Two orbital solutions have been identified that differ primarily in the inclination of the orbit plane. The best fit corresponds to an orbital period, P = 46.263 +/- (0.006)(0.074) days. semimajor axis a = 4660 +/- 170 km and orbital eccentricity e = 0.460 +/- 0.013 corresponding to a system mass in = 3.7 +/- 0.4 x 10(18) kg. For a density of p = 1000 kg m(-3) the albedo at 477 inn is p(477) = 0.12 +/- 0.01 significantly higher than has been commonly assumed for objects in the Kuiper belt. Multicolor, multiepoch photometry shows this pair to have colors typical for the Kuiper belt with a spectral gradient of 0.35 per 100 nm it) the range between 475 and 775 nm. Photometric variations at the four epochs we observed were as large a., 12 3% but the sampling is insufficent to confirm the existence of a lightcurve. (C) 2004 Elsevier Inc. All rights reserved.