May 28, 2014
American Center for Physics
College Park, MD
Date: Wednesday, May 28, 2014 (Please Note: Day and Date)
Speaker: Dr. W. Dean Pesnell, NASA- GSFC
Topic: Helioseismology and Asteroseismology: Oscillations from Space
Time and Location: 1:00 PM, with Q&A to follow; in a 1st floor conference room at the American Center for Physics (www.acp.org), 1 Physics Ellipse, College Park, MD-- off River Rd., between Kenilworth Ave. and Paint Branch Parkway.
Abstract: Variable stars have been our window to the universe for almost four centuries. Cepheid variables are cosmological distance indicators, RR Lyrae stars tell us the distance to globular clusters, and variable white dwarf stars reveal the composition layers within the star. Five minute solar oscillations were first observed in 1966. It was 1975 before they were described as p modes trapped within the solar interior. Over the past 3 decades helioseismology (the study of oscillations of the Sun) has allowed us to scrutinize the inside of the Sun. We can observe the temperature and rotation profiles, boundaries of the convection zone, details of sunspots, as well as the velocities of bulk motion in the Sun. Advances in electronic detectors and putting them above our atmosphere were the biggest changes in variable star observations. The HMI instrument being flown on NASA’s SDO satellite will provide full-disk, high-resolution, Doppler velocity measurements that will advance the field of solar science in ways we did not anticipate. Other orbiting observatories look at the stars in our neighborhood. The Kepler satellite focused on solar-type stars and found oscillations in a wide range of masses. I will discuss what we can learn from helioseismology and asteroseismology (the study of oscillations of stars) and what the future could bring.
Biography: Dr. W. Dean Pesnell is the Project Scientist of the Solar Dynamics Observatory. He has published 95 papers in a variety of research areas, including variable stars, sun-grazing comets, the Sun-Earth connection, quantum mechanics, and meteors in planetary atmospheres. He received his Ph.D. in 1983 from the University of Florida. After a post-doc at the University of Colorado and a visiting professorship at New Mexico State University, Dr. Pesnell moved to Goddard as a contractor in 1990. He formed Nomad Research,Inc. in 1995 to do independent scientific research. One research contract was to design the “Living With a Star” missions to study the response of the Earth to solar activity. He started working on SDO in 2004 and became the Project Scientist in 2005. He has lectured extensively on solar activity, including the recent unusual minimum in solar activity, and predicting solar activity.