Professor Jeff Hester
Arizona State University
jhester@asu.edu
4:15-5:15 Tuesday
April 22,
2003
Abstract
There is no single object in all of astrophysics that has been more heavily studied than the Crab Nebula. Ask most any astronomer about the Crab, and you will likely get an immediate answer. Perhaps that answer will focus on the Crab pulsar -- the first pulsar to be detected at optical wavelengths, and the first and best observational link between pulsar birth and supernovae. Perhaps that answer will stress the historical nature of the Crab supernova, witnessed by Chinese astronomers in 1054 AD. Ask an optical or UV spectroscopist and you will hear about the chemically enriched ejecta from the explosion itself. An infrared astronomer might tell you about the peculiar IR excess from the object, and the possibility of dust emission. Ask a radio astronomer and the Crab will be painted as a plerion. Ask an X-ray astronomer and you will learn that the Crab is the flagship of pulsar wind nebulae. Everyone knows about the Crab.
But when asked to describe the Crab more broadly than their area of specialization, most astronomers will probably fall back on the same basic description of the Crab that they heard in graduate school. The Crab is a free expansion supernova remnant with a pulsar and some synchrotron nebulosity thrown in for good measure. We now understand that description to be fundamentally wrong.
In my talk I will discuss a wide range of observational and theoretical results on the Crab from the last few years, ranging from HST observations and MHD calculations of the filaments to STIS spectroscopy of the pulsar itself. Highlights will include recent HST and Chandra movies showing the remarkable dynamics of the inner synchrotron nebula, the only place in the sky where we can watch an ultrarelatistic magnetized pair plasma with enough spatial and temporal resolution to see how it behaves. (Bring popcorn.) Together, this work has answered many longstanding questions about the Crab, leading to a single unified description of the nebula that may be quite different from the one that you carry in your head.