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The World Year of Physics is a worldwide celebration of physics and its
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Are supernovae round?
Doug Leonard (Astronomy Department, Caltech)
Science Auditorium, CSUCI
October 27th, 3.30 pm
(Come at 3.10 pm for light
refreshments!!)
(Parking for visitors: no citing in car
parks A3 and A4
Details: [email protected]
(805.437.8990)
Can you spot the "new star"? It's supernova 2004dj, which was discovered in the outskirts of NGC 2403, a nearby spiral galaxy, in July of
2004. At about 11 million light-years from Earth, it is the closest such stellar explosion of the past decade, and observations of it continue to
reveal clues to the mysterious explosion mechanism of massive stars.
Roughly once per century in a typical galaxy, a massive star ends its life in a spectacular
explosion that shines with the brilliance of all the billions of other stars in the galaxy
combined. These explosions are called supernovae, and their fleeting presence in the night
sky has been recorded since antiquity. The physical process by which these stars explode,
however, remains a mystery. Conventional wisdom holds that a spherically symmetric
mechanism is at work, one that expels the ejecta equally in all directions. Explosion
geometry has been a difficult subject to tackle because all supernovae in other galaxies are
so distant that they remain point-like in our night sky (and the last one to be witnessed in our
galaxy, the Milky Way, happened during the pre-telescopic era of Johannes Kepler!). Using
very recent evidence derived from a novel observational technique, I will argue that the
innermost regions of these stellar explosions are, in fact, severely distorted, the result of an
explosion mechanism that is strongly non-spherical in nature.
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Douglas Leonard is a National Science Foundation Astronomy and Astrophysics Postdoctoral Scholar at the California
Institute of Technology, where he studies the physics and early-time geometry of supernova explosions, and how this
impacts their use as cosmological distance indicators to reveal details of the origin, evolution, and ultimate fate of the
universe. Dr. Leonard received his Ph.D. in astrophysics from the University of California, Berkeley. His publications
include over 40 articles in the technical literature. A passionate science educator, his latest endeavor has been the creation
of a new course offering at Caltech entitled "Inventing Reality: The Human Search for Truth", which traces the development
of human thought about the physical world (further details: http://www.astro.caltech.edu/~leonard/inventingreality/). In
January, 2006, he will join the faculty at San Diego State University.