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After the Supernova: Pulsars QuickTime™ and a decompressor are needed to see this picture. Melissa Anholm University of Wisconsin-Milwaukee 29 September, 2008 Outline • Properties of Neutron Stars • Large Magnetic Field • Rapid Rotation • Origin of the Pulsing Effect • Motion in a Magnetic Field • Light Emission • The Lighthouse Effect Properties of Neutron Stars A Typical Neutron Star • Strong Magnetic Field • Fast Rotation Properties of Neutron Stars Why does it spin so fast? A typical star completes about one rotation every week - month. QuickTime™ and a decompressor are needed to see this picture. A typical young pulsar completes about one rotation per second. Properties of Neutron Stars Magnetic Fields - Now with Lines! QuickTime™ and a decompressor are needed to see this picture. http://www.freewebs.com/ayxl/magnet.jpeg QuickTime™ and a decompressor are needed to see this picture. http://www.utm.edu/staff/cerkal/magnetic_files/image004.jpg Properties of Neutron Stars After the Collapse: Rotation and the Magnetic Field • Dense magnetic field lines Strong magnetic field • Angular momentum conserved Fast rotation QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. • Magnetic and rotational axes may not be aligned. Origin of the Pulsing Effect Misalignment of Magnetic and Rotational Axes - Why We Care QuickTime™ and a GIF decompressor are needed to see this picture. http://www.atnf.csiro.au/news/press/images/binary_pulsar/ All newly formed neutron stars (and some older ones, too!) produce beams of light along their magnetic poles if the axes aren’t aligned. Origin of the Pulsing Effect Properties of Light • “photon” = a particle of light • accelerating charged particles produce photons (!) Origin of the Pulsing Effect A Strange Connection between Electricity and Magnetism • Moving magnets produce an electric force. QuickTime™ and a decompressor are needed to see this picture. • Electric currents and moving charged particles produce a magnetic force. • Result: a moving charged particle in a magnetic field will accelerate. http://img105.imageshack.us/img105/5114/magfield0ct.jpg Origin of the Pulsing Effect Motion on a Large Scale Near a Rotating Magnet QuickTime™ and a GIF decompressor are needed to see this picture. http://www.atnf.csiro.au/news/press/images/binary_pulsar/ Charged particles move upward or downward (depending on the charge) at the pulsar’s rotational poles. Origin of the Pulsing Effect Motion in a Magnetic Field QuickTime™ and a decompressor are needed to see this picture. • A charged particle placed in a magnetic field will spiral around the magnetic field lines. Origin of the Pulsing Effect Accelerating A Charged Particle • Light is emitted in a direction perpendicular to the magnetic field. QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a decompressor are needed to see this picture. Synchrotron Radiation = Light Origin of the Pulsing Effect The Lighthouse Effect QuickTime™ and a decompressor are needed to see this picture. QuickTime™ and a GIF decompre sso r are nee ded to s ee this picture . http://www.shatters.net/forum/viewtopic.php?t=11372 Conclusions • Pulsars are rapidly rotating neutron stars with powerful magnetic fields. • A misalignment in the rotational and magnetic axes leads to the emission of beams of light from a pulsar’s magnetic poles.