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The Danger of Deadly Cosmic Explosions Supernovae and Gamma Ray Bursts John Learned UH Physics & Astronomy, 4 May 2005 Stars Get Old • Run out of fuel. • Smaller stars – Long (billions of years) boring lives, – Flash before senescence (like the sun). • Big stars (10-100 sun mass), – Live fast (millions of years) – Die young, glorious display… a supernova – Brighter than a galaxy for a few days – More radiation than during whole life of star Sanduleak -69 202 Supernova 1987A 23 February 1987 Tarantula Nebula Large Magellanic Cloud Distance 50 kpc (160.000 light years) Georg Raffelt, Max-Planck-Institut für Physik, München, Germany A Nearby Supernova Can Ruin Your Existence • Deadly from neutrinos within 30 light years. • Atmosphere, weather, ruined. • Major extinction. • Not much harm if further. • SN material in sediments. • 1 SN/100 years in our galaxy • Close 1 per 100million years. • Good news: our neighbors are peaceful. • Bad news: when one shows signs of blowing, it is time to migrate. Gamma Ray Bursts 30 year mystery Brightest flashes seen Usually billions of light years away. Jets from Supernovae? Beaming factor: 340? 10,000? Beams may reach across galaxy. Can happen here! Eta Carinae Ready to Blow? • Brightest star in galaxy – 4 million x sun • Maybe still dangerous at 7000 light years • Fortunately not pointed at us, we think. • Other stars old too… Recent “Soft GR Repeater” in Our Galaxy – SGR 1806-20, 12/27/04 • Brightest X-Ray burst – damaged satellites – affected radio. • Across galaxy, maybe 50,000 light years away. • Rotating neutron star, fantastic magnetic field. • Spectacular, but not lethally dangerous – well, except for astronauts maybe. GRBs Can Zap Us from Across the Galaxy • Narrow beam, confined over galactic distances. • We see GRB in distant galaxies that have most radiation at high energies…. penetrates even underground and underseas. • Equivalent to 1 kiloton TNT / km2 over earth surface, and clearly kills everything immediately exposed. • Longer term destroys atmosphere, brings on nuclear winter. Dar & DeRujula Astro-ph/0110162 The End May be in Sight! • There are galactic hazards to life on earth. • We probably experienced some in the past. • Explain lack of evident life in galaxy? • Cosmic disasters WILL happen eventually, within ~100Million years. • We shall have to leave earth to survive. • But for now, everything is fine, is fine, is fine….