* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download When Stars Attack! In Search of Killer Supernovae
Observational astronomy wikipedia , lookup
History of astronomy wikipedia , lookup
Extraterrestrial life wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
Gamma-ray burst wikipedia , lookup
Rare Earth hypothesis wikipedia , lookup
Dialogue Concerning the Two Chief World Systems wikipedia , lookup
Cassiopeia (constellation) wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Cosmic distance ladder wikipedia , lookup
Corvus (constellation) wikipedia , lookup
Max Planck Institute for Extraterrestrial Physics wikipedia , lookup
H II region wikipedia , lookup
Astronomical spectroscopy wikipedia , lookup
Theoretical astronomy wikipedia , lookup
Star formation wikipedia , lookup
Stellar evolution wikipedia , lookup
Timeline of astronomy wikipedia , lookup
When Stars Attack! In Search of Killer Supernova Explosions Brian Fields University of Illinois Saturday Physics for Everyone Saturday Physics for Everyone October 25, 2014 | Oct 25 2014 Prelude Here at the University of Illinois... we promise the Universe: it’s right there in the name! Today: we deliver! Any Illinois Alumni? Saturday Physics for Everyone | Oct 25 2014 When Stars Attack! ★ Brighter than One Billion Suns Supernova explosions now and in the past ★ Celebrities of the Cosmos Lifestyles and death throes of massive stars ★ Too Close for Comfort Supernova explosions near the Earth ★ Supernova Archaeology Explosion debris from the bottom of the sea Saturday Physics for Everyone | Oct 25 2014 Supernova Explosions Observed Saturday Physics for Everyone | Oct 25 2014 The Fate of Stars Fact: Stars constantly lose energy Fact: Stars have finite mass = finite fuel supply = limited energy Fact: Energy is conserved: No free lunch! Therefore…? Stars can’t live forever All stars must die! Stars have life cycles! Saturday Physics for Everyone | Oct 25 2014 Supernova Explosions The Death of Massive Stars mass > 10 suns Ø Spectacular Ø Rare Ø Crucial for life …but don’t get too close… What do we see? § Bright: can outshine galaxy § Rapid changes in time: max in daysLight from a single dims over weeks supernova § Shock wave launched Fast, ultra-hot gas Saturday Physics for Everyone | Oct 25 2014 Combined light of 100 billion stars Historical Supernovae Supernova explosions are rare: Ø Fewer than 1% of stars die this way Ø None seen in our Galaxy for 300 years The Sun will die… Ø But not this way (not an explosion!) Ø And not for billions of years Ø Sleep well tonight! Saturday Physics for Everyone | Oct 25 2014 Supernova Explosions in Recorded History 1054 AD Ø Europe: no record Ø China: “guest star” 天關客星 Ø Anasazi people Chaco Canyon, NM: painting Modern view of this region of the sky: Crab Nebula—remains of a supernova explosion Saturday Physics for Everyone | Oct 25 2014 Supernova Explosions in Recorded History November 11, 1572 Tycho Brahe A “new star” (“nova stella”) Modern view (X-rays): remains of a supernova explosion Saturday Physics for Everyone | Oct 25 2014 November 11, 1572 Tycho Brahe On the 11th day of November in the evening after sunset ... I noticed that a new and unusual star, surpassing the other stars in brilliancy, was shining ... and since I had, from boyhood, known all the stars of the heavens perfectly, it was quite evident to me that there had never been any star in that place of the sky ... I was so astonished of this sight ... A miracle indeed, one that has never been previously seen before our time, in any age since the beginning of the world. What did Tycho get right? Where was he wrong? Saturday Physics for Everyone | Oct 25 2014 Questions so far? Saturday Physics for Everyone | Oct 25 2014 When Stars Attack! Ø Brighter than One Billion Suns Supernova explosions now and in the past Ø Celebrities of the Cosmos Lifestyles and death throes of massive stars Ø Too Close for Comfort Supernova explosions near the Earth Ø Supernova Archaeology Explosion debris from the bottom of the sea Saturday Physics for Everyone | Oct 25 2014 Supernova Explosions: GettingUnder the Hood Saturday Physics for Everyone | Oct 25 2014 The James Dean of Stars Live Fast gas Star life is struggle vs gravity Million-degree seen in X-ray vision; 300 yrs old Nuclear fires keep hot, pressurized, stable Q: what happens when fuel runs out? Die Young Ø Ø Ø Ø Hot, shocked gas; > 5,000 yrs old Fuel exhaustion collapse Core becomes dense, “bounce” Shock wave launched explosion! Demo: AstroBlasterTM Leave a Beautiful Corpse • Ultradense “cinder” neutron star/black hole • Most material ejected at high speed Saturday Physics for Everyone | Oct 25 2014 : o m e D uid Liq gen ro F t i N 21 -3 The Circle of Life Stars are vast nuclear reactors In hot core: fusion Light elements combine hydrogen helium heavier carbon oxygen … iron New elements ejected at death Ø Stars are source of all but H, He, Li We are made of nuclear ashes of stars Saturday Physics for Everyone | Oct 25 2014 Ashes of Nuclear Furnaces Most nuclear reactions in stars produce healthy, stable atoms But… Some unstable, radioactive atoms are always produced Ø then decay after a certain time For example: Ø Solar system born 4.5 billion years ago with traces of radioactivity Ø Today, our Galaxy contains traces of radioactivity …which can be observed by the high-energy gamma-rays The radioactive sky: itgamma-rays from emits! decays of unstable aluminum-26 atoms D o m e Saturday Physics for Everyone | Oct 25 2014 Questions? Saturday Physics for Everyone | Oct 25 2014 When Stars Attack! Ø Brighter than One Billion Suns Supernova explosions now and in the past Ø Celebrities of the Cosmos Lifestyles and death throes of massive stars Ø Too Close for Comfort Supernova explosions near the Earth Ø Supernova Archaeology Explosion debris from the bottom of the sea Saturday Physics for Everyone | Oct 25 2014 Near-Earth Supernovae Saturday Physics for Everyone | Oct 25 2014 Supernova Explosions Near Earth Cosmic WMD In our Milky Way galaxy: Ø About 1 SN/century Ø Most far away: spectacular but harmless Now: no nearby massive stars Sleep well tonight! But over the 4.5 billion year history of Earth: Many nearby events! Saturday Physics for Everyone | Oct 25 2014 Surgeon General’s Warning: Supernovae are Dangerous to Your Health! Biological damage if too close (un)holy grail: mass extinction due to SN Q: ill effects of cosmic WMD? Direct DNA damage due to high-energy particles (neutrinos) ars e y gh t i l 30 : e c Indirect tan s i fe d a s Radiation damage to atmosphere um m i n v Destruction of Mi ozone layer …which is bad because?... v No protection from ultraviolet (UV) light v Then Sun’s UV unfiltered v Kills small plants/bacteria at bottom of food chain v Damage all the way up Saturday Physics for Everyone | Oct 25 2014 Questions? Saturday Physics for Everyone | Oct 25 2014 When Stars Attack! Ø Brighter than One Billion Suns Supernova explosions now and in the past Ø Celebrities of the Cosmos Lifestyles and death throes of massive stars Ø Too Close for Comfort Supernova explosions near the Earth Ø Supernova Archaeology Explosion debris from the bottom of the sea Saturday Physics for Everyone | Oct 25 2014 Supernova Archaeology Saturday Physics for Everyone | Oct 25 2014 The Smoking Gun: Supernova Debris on the Earth Ellis, BDF, & Schramm 1996 Explosion launched at ~few% speed of light Slows as plows thru interstellar matter Earth “shielded” by solar wind If blast close enough: ✓ overwhelms solar wind ✓ SN material dumped on Earth ✓ Accumulates in natural “archives” sea sediments, ice cores Q: How would we know? Need observable SN “fingerprint” Nuclear Signature X Stable nuclides: don’t know came from SN ü Live radioactive isotopes: none left on Earth If found, must come from SN! Saturday Physics for Everyone | Oct 25 2014 BDF, Athanassiadou, & Johnson 2006 Sun 1 AU = Earth’s orbit Incoming blast Saturday Physics for Everyone | Oct 25 2014 Evidence? Deep Ocean Crust Knie et al. (1999) ferromanganese (FeMn) crust Pacific Ocean growth: ~ 1 mm/Myr Ultra-high sensitivity measurements accelerator mass spectrometry: “needles in haystacks” discovered live radioactivity present! 60Fe, ! Q: What pattern expected in sediment? Expect: one radioactive layer 1999: 60Fe in multiple layers!? Saturday Physics for Everyone | Oct 25 2014 60Fe Confirmation Knie et al (2004) Advances New crust from new site ✓Better geometry (planar) ✓better time resolution radioactive timescale ✓10Be Woo hoo! Isolated Signal t = 2-3 Million years ago Background: A Landmark Result ★ Isolated pulse identified ★ Epoch quantified ★ Consistent with original crust Note fantastic AMS sensitivity! Saturday Physics for Everyone | Oct 25 2014 60Ni Aftermath: The Local Bubble? ★ The Sun lives in region of hot, rarefied gas – The Local Bubble – huge hot cavity ~150 light yrs – seen via foreground absorption in nearby starlight ★ Nearby SN needed to blow bubble! – we live inside SN remains – bubble models require >> 1 SN in past 10 Myr Smith & Cox 01 – 60Fe event from nearest massive star cluster? Benitez et al 00 29 Saturday Physics for Everyone | Oct 25 2014 A Near Miss? Supernova debris more dispersed at greater distance can relate measured amount to distance! #60 Fe atoms ∼ ➡find range 1/d2 d=60-300 light years So d>dkill ...but barely: "near miss" ¿ Climate change from radiation? ¿ bump in extinctions? Image: Mark Garlick www.markgarlick.com If true: implications for astrobiology tightens Galactic habitable zone Saturday Physics for Everyone | Oct 25 2014 Other Signals? Radioactive Fossil Bacteria reported April 2013 -magnetotactic bacteria synthesize magentite nanoparticles (Fe3O4) -incorporate & concentrate ocean Fe -60Fe spike seen ocean sediment! -coincident in time with crust data! Lunar Soil ★ consistency check for deep-ocean signal ★ but: nontrivial background: cosmic-ray activation of lunar regolith Cook et al 2010 2-page conference proceeding! ★ 60Fe excess in top layer of lunar drill core ★ signal amplitude (surface density) smaller than deep-ocean sample Alan Bean, Apollo 12 (1969) 31 Saturday Physics for Everyone | Oct 25 2014 Outlook Summary and Conclusions ★ Live radioactive iron (60Fe) seen in two deep-ocean crusts ★ Signal isolated to ~3 Myr ago Birth of “Supernova Archaeology" Implications across disciplines: astronomy, physics, astrobiology, evolutionary biology Future Research ★ better model of SN impact on solar system ★ improved SN radioactive synthesis models ★ more, different samples: Ø other kinds of radioactive atoms (isotopes) Ø other sites (lunar samples?) ★ other epochs? Mass extinction correlations? ★ Stay tuned... Saturday Physics for Everyone | Oct 25 2014