Volume Visualization of the Evolution of an Emission Nebula
Volume Visualization of the Evolution of an Emission Nebula
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The galaxy contains tens of thousands of dark nebulae, so-called because the dust and gas obscure the light of stars behind them. Over time clumps of higher density gas form and grow within some of these, their gravitational attraction drawing matter from the surrounding cloud. As a clump grows, the weight of layer upon layer of gas builds up, increasing the pressure and temperature at the clump's core. The pressure continues to rise until hydrogen nuclei are packed so tightly together that they fuse, igniting a thermo-nuclear reaction that signals the birth of a star. Nebula are the birthplace of stars.
Hot young stars born within the nebula radiate their energy outward into the surrounding gas. High-energy photons from the stars ionize the atoms of the gas, knocking electrons from their orbits. As these electrons collide with other electrons and slowly return to their former orbits, they emit light. It is this light we see as the eerie glow of an emission nebula.
Since electrons can reside in atoms only in discrete energy levels, when electrons drop from outer to inner orbits they emit light at discrete wavelengths. By examining the spectra of nebulae, astronomers deduce their chemical content. Most emission nebulae are about 90% hydrogen, with the remainder helium, oxygen, nitrogen, and other elements. Ionization of these gases gives nebulae many of the colors we see in astronomical photographs.
Working with scientists at the American Museum of Natural History (AMNH), visualization experts at the San Diego Supercomputer Center have created an animated flight into the heart of a newly formed emission nebula. As time streams past at millions of years per second, the cold dust and gas of the interstellar medium swirls and gradually condenses into high-density clumps. A star ignites and the surrounding gas ionizes into shades of red and green. Our flight path dives into the center where we find the young blue-white star and a surreal environment of glowing gas.
The visualization is as true as today's science can make it. Underlying the visualization is 2.5 terabytes - 2.5 million megabytes - of data generated by supercomputer simulation run by Mordecai Mac Low, Assistant Curator of the Department of Astrophysics at the American Museum of Natural History. The simulation was run at the National Center for Supercomputing Applications (NCSA) in Champaign-Urbana Illinois. Transfered to SDSC via the Internet2, the data was processed and rendered using over 1000 processors of SDSC's Blue Horizon supercomputer. The final animation boasts over 40,000 images.
Visualizations by:David R. Nadeau, Erik Engquist,
San Diego Supercomputer Center, University of California, San Diego.
Direction by:
Anthony Braun (producer), Carter Emmart, Ryan Wyatt, Erik Wesselak, Christopher Scollard, Clay Budin, Mordecai Mac Low
Hayden Planetarium, American Museum of Natural History, New York.
Data by:
Stuart Leavy, Bob Patterson
National Center for Supercomputing Applications (NCSA),
Champaign-Urbana, Illinois.
Ryan Wyatt, Clay Budin, Mordecai Mac Low and Li, Norman, Heitsch, and Oishi
Hayden Planetarium, American Museum of Natural History, New York.
Tom Abel
Pennsylvania State University
John Hawley
University of Virginia
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