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Schedule Items

Schedule Items. Feb 28 (tomorrow): Colwell lecture, “The Future of Science” 4 PM McKeldin March 9 (Saturday): Udvar Hazy excursion April 20-21: SDU in Philadelphia. Sign up prior to winter break! Penny Wars!. Death from Above!. February 15, 2013.

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Schedule Items

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  1. Schedule Items • Feb 28 (tomorrow): Colwell lecture, “The Future of Science” • 4 PM McKeldin • March 9 (Saturday): Udvar Hazy excursion • April 20-21: SDU in Philadelphia. Sign up prior to winter break! • Penny Wars!

  2. Death from Above!

  3. February 15, 2013 • At about 9:20 AM, a glowing streak crossed the sky near Chelyabinsk, Russia. There was a huge flash, and about a minute later the sound wave pounded the city. • Over 1500 people with injuries, mostly from shattered glass • Estimated $33M in damages

  4. Location of Chelyabinsk

  5. Digital Age • There are many pictures and videos, especially from dashboard cameras on vehicles • Popular in Russia for personal protection in events of traffic incidents • Many quickly made it onto Youtube • Stations for nuclear test ban compliance pick up shock wave as far as 15,000 km away (Antarctica!)

  6. Details • Believed to be a 17-meter diameter meteor, coming in at about 18 km/s before bursting in the atmosphere • Small cm-sized fragments found, possibility of larger pieces is open • Chondritic, ~10% iron/nickel

  7. Lake Cherbarkul

  8. Always Compared toAtomic Weapon Yields • Explosion of about 500 kiloton • Refers to equivalent in TNT • In SI units, 1 kt = 4.184e12 Joules • Atomic bombs used in WWII estimated at around 12.5 kt • Where does this number come from? • Power from shock wave (“infrasound” stations) • Simple physics!

  9. Calculation • E = ½ mv2 • m = ρV • V = 4/3 π R3 • Chondritic type, average density is about 3.4 g/cm3 • Get pretty close to 10,000 tons • Get reasonably close to 500 kt Chondritic Meteorite Credit: H. Raab

  10. Orbit Calculation • Clever fellow uses Youtube video of Revolution Square, Google Earth for dimensions and distances of street lamps, and geometry • Stefan Greens • Pair of Colombian scientists take it and run with it • Zuluaga & Ferrin

  11. Probable Orbit

  12. You Poor Fool.You Actually Believe This? • Conspiracy theories abound. A Russian news group conducted a poll which suggested about half of the people didn’t think it was a meteorite! • Controversial member of parliament blames US weapons test • Some think it was Russian military • Aliens! Deadly virus delivered from space!

  13. Watching the Skies • Near Earth Objects (NEOs) include asteroids and comets with perihelion distances under 1.3 AU • Potentially hazardous objects are the subset with orbits close enough to the Earth (~0.05 AU) and large enough to cause significant damage • Most come from asteroid belt through gravitational interactions and collisions • Only survive in NEO orbits for millions of years

  14. Dangers of NEOs • Power Law distribution of material • Lots of little stuff • Small amount of big stuff • About 100 tons of material a day hits Earth! • In rough terms, objects 5 - 10 m in size have the energy of the Hiroshima atomic bomb and hit the Earth roughly yearly • Mostly vaporize in upper atmosphere • Larger objects, ~50 m in size, hit roughly every thousand years • km size objects hit every million years or so • Numbers rough – to within factors of a few

  15. Asteroids in Inner Solar System From IAU Minor Planet Center See animation!

  16. What They Can Do: K-T • Geological boundary, roughly 65 million years ago • Below it, dinosaur fossils • Above it, only mammalian and birds • Mass extinction event • Layer in between very rich in irridium: not found in surface rocks (differentiation of Earth’s core), hence association with a large impact (or multiple ones) • Probable object size in kms • Scientific debate still continues

  17. What They Can Do: Tunguska • Tunguska 1908 • Siberian forest region • ~15 megaton air burst; roughly the energy of the largest thermonuclear device ever • Object probablyaround 50meters across • Flattens tens of millions of trees, about a thousand square miles 1927 photo from Soviet Academy Of Sciences; Kulik

  18. Congressional Mandates • 1998 “Spaceguard” • Detect 90% of all NEOs over 1 km in diameter by 2008 • Roughly the 1000 objects large enough to cause major catastrophes • 2005 “George E. Brown, Jr. Near-Earth Object Survey Act” • Detect 90% of all NEOs over 140 m in diameter by 2028 • Roughly the 100,000 objects large enough to cause significant damage

  19. NEO Observations • NASA/JPL program catalogs and tracks them • Nearly10,000 NEOs identified so far • Currentlyalmost 1400 PHAs • Multiple observatories/programs have grants through program

  20. Doing Pretty Well With Large Ones Recent NEOWISE results suggest we’ve found 93% of all big ones (maybe 70 remain)

  21. Sample of NEO Observatories • Generally small telescopes, wide area • Spacewatch (Kitt Peak) • Lincoln Near-Earth Asteroid Research (LINEAR) • Lowell Observatory Near-Earth Object Search (LONEOS) • Catalina Sky Survey • Near-Earth Asteroid Tracking (NEAT) • NEOWISE (infrared survey satellite telescope, program to find NEOs)

  22. Next Generation • Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) • Large Synoptic Survey Telescope (LSST)

  23. Not Just Gloom & Doom • There’s science, too • They are remnants from the formation of the Solar System some 4.6 billion years ago • Supply of water and building blocks for life?

  24. Other Recent Strikes • 2002 over Eastern Mediterranean sea • Estimated 26 kt (from sound wave), 10m diameter object • 2009 Indonesia • Similar size as Mediterranean, roughly double the energy (volume goes as cube so slightly larger means a lot) • 2008 Sudan: small but really cool!

  25. Sudan Impact Predicted • NEO named 2008 TC3 • Data show it will impact the Earth on October 7 over Sudan • Less than 21 hours after discovery! • National agencies notified, NASA press release

  26. Impact Confirmed • Seen by satellites (government and weather), a commercial aircraft, ground sightings, and infrasound • Latter from blast as it explodes in atmosphere, energy about 1 kT TNT at 37 km altitude • These numbers match predictions based on NEO brightness Weather satellite image, red spot is airburst

  27. Searching for Meteorites • Trail seen over Sudan, in Nubian desert • NASA/SETI astronomer works with University of Khartoum faculty member • Use JPL trajectories, search grid, find remnants! APOD images; Jenniskens, Shaddad

  28. Conclusion • We live in an age where information is accessible and recorded observations are everywhere • We get to learn about events that are fairly rare! • We can use them to act responsibly • There’s a web page of links for this lecture, and you can find MANY videos on Youtube. Have fun!

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