Astronomy and Astrophysics
Several faculty members work on astronomy/astrophysics or physics with astronomical applications:
- J. P. Caillault
(stars and star forming regions)
- Coates Johnson (emeritus, general relativity with astronomical applications)
- Loris Magnani (molecular clouds and the diffuse interstellar medium)
- Scott Shaw (binary and variable stars)
- Robin Shelton (bubbles blown by supernova explosions and hot interstellar gas)
- Phillip Stancil (theoretical laboratory astrophysics and astrochemistry).
Some specific areas of research are:
Binary and Variable Stars:
Eclipsing binary stars orbit each other and so periodically one star can block our view of the other. By searching for periodic variations in
their light intensities, Dr. Scott Shaw and collaborators in the Research Experience for Undergraduates program
have identified thousands of previously unknown binary star pairs. The 0.9m telescope of the Southeastern Association for Research in
Astronomy (SARA) is operated remotely from the UGA campus to monitor the light
curves of a large variety of eclipsing and variable stars.
Stellar Ages and Constraints on Planet Formation:
Stars like Vega are thought to be orbited by disks of dusty material from which planets may be forming. Dr. J. P. Caillault
and collaborators (including his former graduate student, Inseok Song) have used infrared and X-ray observations to determine the ages of
Vega-like stars and thus determine the timescale during which their disks may have evolved.
Clouds of Cold Gas in the Galaxy:
The Galaxy is filled with clouds of cold, cool, warm, and hot gas. Molecules abound in the denser cold regions. Dr. Loris Magnani and
collaborators use the Arecibo 305 meter radio telescope in Puerto Rico and the Green Bank 100 meter radio telescope in West Virginia
to search for C-H and C-O molecules throughout the galaxy. For instance, a recent survey of CH in the direction of the Galactic
Center revealed a very different distribution of molecular gas than what is normally seen with CO and its isotopes. This difference is
probably attributable to the tendency of the CH 3335 MHz transition to trace lower density gas than the CO rotational transitions. By studying
this low-density molecular component, Dr. Magnani hopes to understand the connection between the atomic and molecular gas phases in the
Galaxy.
In addition, Dr. Loris Magnani and Ray Chastain (grad student, UGA) have found a previously unidentified ring of molecule-rich gas. They have suggested that it may be the edge of a bubble blown by the winds of a hot star.
Atomic and Molecular Calculations with Astrophysical Applications:
Astronomy relies on observations of light from planets, stars and gas. In order to interpret many observations, we need accurate estimates
of atomic and molecular constants, rates, and probabilities. Dr. Phillip Stancil and collaborators at UGA and throughout the world use a fully
quantum-mechanical technique in order to calculate such quantities. Their results for LiCl have been incorporated into the PHOENIX computer code
(written by Dr. Peter Hauschildt, formerly of UGA) which predicts stellar spectral signatures. By comparing the model
predictions with observations, it is hoped that it will be possible
to predict the abundance of lithium in cool dwarf stars.
Lithium is a particularly important element because the big bang produced lithium. Dr. Stancil and collaborators have tracked the early history of lithium and and its effect on the cosmic microwave background anisotropies.
Supernova Remnants and Hot Gas in our Galaxy:
Some stars end their lives by blowing up. The explosions blow giant bubbles of hot gas which glow in ultraviolet and X-ray light.
By comparing the X-rays emitted by an unusual looking supernova remnant named W44 with computer simulations, Dr. Robin Shelton and collaborators
were able to determine the astrophysical causes of this remnant's strange appearance. This particular remnant is the epitome of its class of
remnants so the new explanations presumably apply to others in its class. Recently, Dr. Robin Shelton and collaborators at NASA found another, similar remnant to add to the list.
When considered as a group, supernova remnant bubbles constitute most of the hot gas in our (and other) galaxy. This hot gas affects the ecology of a galaxy in many ways and therefore must be understood in order for the galaxy to be understood. Dr. Shelton and Dr. Elizabeth Raley (post doc, UGA) perform computational simulations of supernova remnant bubbles in order to track their expansion, movement, effect on surrounding material, observables, and lifetime. For more information on computer simulations, click here