1. Danger The Danger of Deadly Cosmic Explosions Supernovae and Gamma Ray Bursts John Learned UH Physics & Astronomy, 4 May 2005

2. 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

3. Sanduleak  69 202 Large Magellanic Cloud Distance 50 kpc (160.000 light years) Tarantula Nebula Supernova 1987A 23 February 1987 Supernova 1987A 23 February 1987 Georg Raffelt, Max-Planck-Institut für Physik, München, Germany

4. A Nearby Supernova Can Ruin Your Existence DeadlyDeadly from neutrinos within 30 light years. Atmosphere, weather, ruined. Major extinctionMajor extinction. Not much harm if furtherNot much harm if further. SN material in sediments. 1 SN/100 years in our galaxy Close 1 per 100million years. Good newsGood news: our neighbors are peaceful. Bad newsBad news: when one shows signs of blowing, it is time to migrate.

5. 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!

6. 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…

7. 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.

8. 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. 1 kiloton TNT / km 2Equivalent to 1 kiloton TNT / km 2 over earth surface, and clearly kills everything immediately exposed. Longer term destroys atmosphere, brings on nuclear winter. Dar & DeRujula Astro-ph/0110162

9. The End May be in Sight! areThere are galactic hazards to life on earth. We probably experienced some in the past. lack of evident life in galaxyExplain lack of evident life in galaxy? WILL happenCosmic disasters WILL happen eventually, within ~100Million years. leave earthWe shall have to leave earth to survive. everything is fineBut for now, everything is fine, is fine, is fine….