Astronomy and Astrophysics

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Several faculty members work on astronomy/astrophysics or physics with astronomical applications:

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.

Hot Gas in our Galaxy:

Some stars end their lives by blowing up.  The explosions, called supernova, blow giant bubbles of hot gas which glow in ultraviolet and X-ray light.   When considered as a group, supernova remnant bubbles constitute most of the hot gas in our galaxy.    This hot gas affects the ecology of the galaxy in many ways and therefore must be understood in order for the galaxy to be understood.  Dr. Elizabeth Raley (former post doc, UGA) and Dr. Robin Shelton (faculty, UGA) have performed 3-dimensional magneto-hydrodynamic computational simulations of supernova remnant bubbles, from which they learned about the bubbles' expansion, movement, effects on surrounding material, observables, and lifetime.

Most of the stars in our galaxy are near the plane of the Milky Way and so most of the supernova bubbles are also near the plane.  This makes the outliers that reside above the plane all the more interesting.   Few have been seen, but Dr. David Henley (post doc, UGA) and Dr. Shelton recently found another.  By carefully examined a suspiciously arc-shaped region of hot, X-ray emitting gas, they found the highest supernova bubble in the Galaxy.  Currently, they are sifting through X-ray observations along various other directions in order to find clues about the history and behavior of our Galaxy.  Mr. Shijun Lei (grad student, UGA) is also working on X-ray observations of hot gas in our galaxy. 

Our galaxy is not alone.  There is a collection of satellite galaxies orbiting it and a swarm gas clouds surrounding it.  Many astronomers think that galaxies grow by accreting such clouds, which can be as massive as a million times the Sun's mass.  However, because the  clouds move with speeds of over 100 kilometers per second (200,000 miles per hour), their merging with our galaxy is not a gentle process.  Dr. Kyujin Kwak (post doc, UGA) and Dr. Shelton are simulating the cloud-galaxy collisions.  Click here for an example.

When not working on computer simulations or X-ray observations, we are working on UV observations.  For more information on computer simulations done within the Department of Physics and Astronomy, click here