_Dr. Michael A. Pahre
Senior Physics Author, Ergopedia, 2011-
From Astrophysicist to Physics Educator
Beginning in elementary school, I was already fascinated by planets, stars, and galaxies. Every science fair project I did was something about astronomy. By the time I entered college, it felt natural to major in physics or astronomy--or both, as it turned out. I began doing astronomy research one summer in college, felt the lure of observational astronomy, and knew where I was headed.
But a funny thing happened on the way to graduate school: I went off to Africa to teach physics in a rural secondary school as a volunteer in the U. S. Peace Corps. I found teaching exciting, challenging, and above all, invigorating. Upon returning I dove into a career as a research astrophysicist. For two decades I traveled to observatories on mountaintops around the globe. I spent night after night collecting data on galaxies and their evolution. I co-authored dozens of papers, wrote even more observing proposals, raised funding for my research, supervised student research projects, and worked on a space mission. I became a rocket scientist. But the itch for teaching never left me during those twenty years. I still wanted to bring some of the wonders of the universe back to the students of our next generation; that's why I decided to work at Ergopedia. My guiding principle: it shouldn't take a rocket scientist to understand or teach physics. Read my curriculum vitae (CV) |
Teaching Physics in Nkroful, Ghana
My first teaching experience was over twenty years ago when, fresh out of college, I served as a Peace Corps Volunteer. I taught physics at Nkroful Agricultural Secondary School in the West African country of Ghana.
Located a few miles from the coast, it rained far more in Nkroful--more than 100 inches per year--than I ever expected to experience in Africa. Virtually every horizon was dominated by plantations of coconut trees, much of it harvested to create coconut oil for export. While the town had a population of only a couple thousand people, it was well-known across Ghana as the birthplace of Kwame Nkrumah, the country's first prime minister and president after gaining its independence in 1957. |
_Infrared Array Camera for the Spitzer Space Telescope
__Prior to joining Ergopedia, for thirteen years I worked at the Smithsonian Astrophysical Observatory (SAO) in Cambridge, MA on a scientific instrument that launched in
2003 on NASA's Spitzer Space Telescope--the infrared companion
observatory to the Hubble Space Telescope. Many astrophysical objects--such as protostars, brown dwarfs, starburst galaxies, and galaxies in the early universe--are
substantially brighter at infrared than visual wavelengths. Spitzer can therefore see many phenomena, such as star
formation and dust emission from the interstellar medium, that are not accessible
at the wavelengths of Hubble's instruments.
The Spitzer Space Telescope carries three scientific instruments. The Infrared Array Camera (IRAC) is sensitive to the shortest infrared wavelengths--and has the highest angular resolution--of the three Spitzer instruments, making it the workhorse throughout the mission. Dr. Giovanni Fazio of SAO is the principal investigator for the IRAC instrument. I joined the science team in 1998 and the instrument team in 2001. (Video credit: NASA)
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_The IRAC instrument was developed over the course of two decades by a
team of scientists and engineers around the country--the Smithsonian Astrophysical Observatory (SAO), Ames Research Center (ARC), Goddard Space Flight Center (GSFC), the University of Arizona (UA), and the University of Rochester (UR). The
three scientific instruments were integrated at Ball Aerospace in
Boulder, Colorado. Lockheed Martin in Sunnyvale, California the integrated the instruments with the
spacecraft.
The Spitzer Space Telescope launched on August 25, 2003 from the Kennedy Space Center at Cape Canaveral, Florida, on a Delta II Heavy vehicle (Delta 7920H-10L). Since it is an infrared observatory, the best view of the launch is using an infrared video [at left]. You can see the rocket pass through the obscuring water vapor of a low cloud soon after lift off! _(Images credit: NASA)
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First images from the Spitzer Space Telescope
_Our IRAC team worked for three months after launch to commission the
instrument in-flight. Near the end of those three months, the telescope was
ready to take images to demonstrate to the public its new, powerful capabilities.
One of the first science images we took with the observatory was of nearby galaxy Messier 81. It shows the smoothly distributed blue emission of starlight from the galaxy as being visually and distinctly separate from the red emission of dust from the star-forming regions in its spiral arms. The image soon became the defining image of the Spitzer mission. It has appeared throughout the web, on the cover of popular astronomy books, on coffee mugs and Christmas tree ornaments--and, now, when combined with images from the GALEX Telescope and the Hubble Space Telescope, on the cover of Ergopedia's Essential Physics. |
Mosaic of Galaxies in the Nearby Universe
Image of an elliptical galaxy.
_Galaxies come in many types: smooth and round elliptical galaxies;
spiral galaxies, with their arms and possibly a bar; and the ubiquitous
irregular galaxies. Galaxies also vary in luminosity from the monster
galaxies at the centers of clusters to dwarf and irregular galaxies,
such as the Large Magellanic Cloud orbiting our own Milky Way Galaxy.
The mosaic of galaxies on the rightare sorted from elliptical galaxies
[left] to spiral galaxies [right], and from low-luminosity galaxies
[bottom] to luminous ones [top].
Images of galaxies at infrared wavelengths can distinguish among each galaxy's components: the stars (blue color); dust from the interstellar medium (red color); and the possible presence of an active nucleus at its center (powered by a supermassive black hole). In the mosaic of galaxies, you can see how the elliptical galaxies are dominated by starlight, with only the occasional hint of dust. The arms of spiral galaxies show up in dust emission, indicating that star formation is occurring there. |
Andromeda galaxy's past encounter
_The nearest spiral galaxy to our own is Messier 31, the Andromeda
Galaxy. We imaged the galaxy at infrared wavelengths and saw unusual
warps in the galaxy's spiral arms--in both its outer and inner
disk--that are indicative of an encounter with another, smaller galaxy.
We then constructed computer simulations of possible scenarios for that
encounter, coming to the conclusion that one of its companion galaxies,
compact elliptical Messier 32, likely plunged through the core of the
Andromeda Galaxy in a polar encounter, leading to the strange warps.
Elliptical Galaxies
_As a graduate student at the California Institute of Technology
(Caltech) in 1993-1994, I helped build a near-infrared imaging camera
for the 60-inch Telescope at Palomar Observatory. At the time, these
256x256 pixel near-infrared array detectors were new to astronomy and considered
cutting-edge--some infrared astronomers were still using single detector
bolometers in those days. An astronomer wields a wide variety of
tools--physics, electronics, optics, machining, computer programming,
data analysis, and so on--all of which are needed in an instrumentation
project.
After successfully commissioning the instrument, I proceeded to observe nearly two hundred nights with that instrument on the telescope. Those data eventually became the first half of my dissertation; it received the 2001 Trumpler Prize of the Astronomical Society of the Pacific for the top astronomy dissertation in North America. The dissertation tied together observations of the properties of nearby and distant elliptical galaxies in order to create a unified picture of how this class of galaxies formed early in the universe's history and subsequently evolved up to their present day form. |