The Danger of Deadly Cosmic Explosions

1. The Danger of Deadly Cosmic Explosions John Learned UH Physics & Astronomy A736/P711 19 April 2005

2. Extinctions of Species on EarthShows Massive Events, but Due to What? Many hypotheses, none sure. At least some due to impacts since we see the craters, plus other evidence. Terrestrial scientists say weather changes, vulcanism. But what caused those?

3. Later classes have larger brains. Time difference around 100 million years. Jim Annis

4. Dangerous Cosmic Events • Direct Impact … happens for sure, but consequences uncertain. (Not discussed further here.) • Solar Novae … seen in other stars, but we do not know enough about our sun. (Not discussed here). • Supernovae … happens for sure, and if a few (<10?) pc away will be deadly. • Gamma Ray Bursts … also surely have happened, but nowadays? Rate? Lethality? Possibly deadly from across galaxy. • AGN Jets … Not so many recently, though M87, but not apparent imminent danger.

5. AGN Jets, Bad but Not Here Soon M87 at 60MLyr… fortunately not pointing at us. Does seem to be swinging around though…

6. Markarian 421 Blazar, pointing at us Around 360 MLyr away No danger, but impressive

7. In our Milky Way galaxy: About 1 SN/century 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! Supernova Explosions Near Earth Next 10 slides from B. Fields, edited by jgl

8. November 11, 1572Tycho 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.”

9. Minimum safe distance: About 30 light years Note: nearest star is 4 light years How Close is Too Close? 30 light years

10. Biological damage if too close (un)holy grail: mass extinction due to SN Direct DNA damage due to high-energy particles (neutrinos) Indirect Radiation damage to atmosphere Destruction of ozone layer …which is bad because?... No protection from ultraviolet (UV) light Then Sun’s UV unfiltered Kills small plants/bacteria at bottom of food chain Damage all the way up Surgeon General’s Warning:Supernovae are Dangerous to Your Health!

11. Explosion launched at 10% speed of light! Slows as plows thru interstellar matter Earth “shielded” by solar “wind” of particles If blast close enough: pushes solar wind away SN material dumped on Earth Accumulates in natural “archives” sea sediments, ice cores Q: How would we know? Need observable evidence: “fingerprint” of SN Nuclear Signature Stable atoms: don’t know came from SN Radioactive atoms: none left on Earth If found, must come from SN! Q: what pattern expected in sediment? The Smoking Gun:Supernova Debris on the Earth

12. Measured by German team ferromanganese (FeMn) crust Pacific Ocean growth: ~ 1 mm/Myr live radioactive iron atoms 60Fe ! a few dozen atoms total (!) 60Fe found in all layers? Q: possible explanations? Deep Ocean Crust1998 Amount of radioactive iron Depth in crust=time deposited

13. Advances New crust from new site Better geometry (planar) better time history Isolated Signal A Landmark Result Isolated pulse identified Epoch quantified Consistent with original crust 60Fe ConfirmationKnie et al (2004) Woo hoo! Amount of radioactive iron Instrumental “noise”: 60Ni Depth in crust=time deposited Note fantastic AMS sensitivity!

14. Whodunit? If SN: nearby, recent Cluster of newborn massive stars (OB association) may still exist maybe source of Local Bubble (hot, rarefied gas surrounding solar system)? Sco-Cen OB Association Benitez et al 2000 ~400 light years away now But was closer 3 Myr ago! 60Fe & 53Mn in Deep Ocean Crust

15. A Near Miss? ...but barely: "near miss" • Climate change from radiation? • bump in extinctions? If true: implications for astrobiology tightens Galactic habitable zone

16. Neutrinos from Nearby SN Can be Lethal to All Life, r<10 pc Low energy but heavily Ionizing nuclear recoils are very dangerous! Juan Collar, 1995

17. Increased Rate at Arm Crossings? Leitch and Vashist, 1998

18. Brian C. Thomas1 A.L. Melott1, B.S. Lieberman1, C.M. Laird1, L.D. Martin1, M.V. Medvedev1, J.K. Cannizzo2, N. Gehrels2, & C.H. Jackman2 1. University of Kansas, Lawrence, KS 66045 USA 2. NASA Goddard Space Flight Center, Greenbelt, MD 20771 USA Did a Gamma-Ray Burst initiate the late Ordovician mass extinction? Next 15 slides from these guys… but edited by jgl.

19. GRBs At least five times in the history of life, the Earth experienced mass extinctions that eliminated a large percentage of the biota. Many possible causes have been documented, and gamma-ray bursts (GRB)1 may also have contributed. A GRB within our own galaxy could do considerable damage to the Earth's biosphere2-4. Estimates2 suggest that a number of nearby GRB have irradiated the Earth since life originated. The late Ordovician event shows many characteristics that would be expected if it were initiated by a nearby GRB.

20. Terrestrial Consequencesof a Nearby GRB Consequences of a GRB depend on observed flux, not intrinsic total energy. Lack of knowledge of the poorly constrained5 recent GRB rate is a serious source of uncertainty in estimating the role they may have played in mass extinctions. At least 3-10 GRB per Gy should occur within a few kpc, irradiating the Earth2,3, with the lower estimate resulting from assuming proportionality to a strongly evolving star formation rate.

21. Prompt burst effects Most of the gamma rays are degraded by interaction with the atmosphere. Prompt UV flux at the surface6 could still exceed existing levels by about one order of magnitude. Most of the burst energy incident upon the atmosphere goes into ionizing it. It is unlikely that most beamed cosmic rays would be energetic enough (>1018eV) to travel nearly undeflected by galactic magnetic fields and arrive at Earth coincident with the photon burst, so most will scatter and add a contribution comparable to the supernova background. Disputed by others! Thus, the instantaneous biotic effects of GRB will be moderate and confined to the facing side of the Earth. Others say opposite!

22. Long-term effects Long-term effects of GRB would spread around the Earth and include ozone layer depletion, global cooling, acid rain, and radionuclide production. The chemical effects7 result from ionization and dissociation of molecules of N2 and O2. The resulting highly reactive products form various oxides of nitrogen. Nitric acid exceeding anthropogenic levels is a probable product2. Global cooling is expected8 from the absorption of visible light by NO2. Substantial ozone depletion will result from NOx constituents, which catalyze conversion7 of ozone to oxygen molecules. Ozone absorbs biologically damaging solar UV radiation before it reaches the surface, so its depletion may have strong consequences. A GRB may have paradoxically produced darkened skies and heightened UV radiation.

23. Damage to marine organisms Modest increases in UV flux around 300 nm, can be lethal to a variety of organisms9,10, including the phytoplankton which are the basis for the marine food chain as well as oxygen production. UV is attenuated by water, though the precise absorption is heavily dependent upon particulatesand dissolved organics10. Penetration depths vary from meters to tens of meters. As would be expected, UV effects on microorganisms have been found to decrease with water depth11.

24. Patterns of Ordovician Extinction The late Ordovician is one of the largest mass extinctions in terms of its scale and scope. It appears to comprise two large, abrupt extinction events, separated by 0.5-2 million years12,13, and all major marine invertebrate groups show high rates of extinction during this interval. The late Ordovician is unusual in that many groups like the trilobites, important Ordovician animal groups in terms of their relative abundance, diversity, and geographic range14, go extinct while the more restricted taxa persist15. This is counterintuitive because one might predict that (due to stochastic factors) widespread, more abundant groups should be more extinction resistant.

25. Typical Ordovician organisms www.ucmp.berkeley.edu/ordovician/ordovician.html Image Courtesy W. Berry, University of California Museum of Paleontology

26. Depth Dependence of Late Ordovician Extinctions One factor that correlates well with likelihood of extinction in trilobites is the amount of time a typical organism spent in the water column. Trilobites that appear to have been pelagic as adults, or are inferred to have had a planktonic larval phase, were much more likely to go extinct15. In fact, it appears to not only be whether the larvae were planktonic but the amount of time the larvae spent in the plankton: longer planktonic larval phases, when such are inferred, are associated with increased extinction probability relative to shorter planktonic larval phases. This in turn partly explains the counterintuitive result: marine invertebrate species with a pelagic adult or a planktonic larval type typically had a broader geographic range16. During the late Ordovician, species dwelling in shallow water were also more likely to go extinct than species dwelling in deeper water13.

27. Global Cooling and the Ordovician Extinction This extinction has been related to alternating global cooling and warming correlated with the two pulses of the late Ordovician mass extinction12,13,17. We do not dispute the role global cooling may have played in mediating this extinction. Instead, we emphasize that there may be a link between GRB and global cooling. GRB produce atmospheric nitrogen dioxide. Its opacity provides a natural mechanism to initiate global cooling. Climate models of the Ordovician show that it is difficult to initiate glaciation without a forcing impulse, such as a period of reduced sunlight18.

28. Ordovician/GRB Connection? We suggest that the late Ordovician mass extinction may have been initiated by a nearby GRB. The oxygen level of the atmosphere was not greatly different from that of the present19, so that an ozone shield should have been in place. Its destruction followed by greatly increased solar UV would almost certainly involve similar catastrophic consequences to those observed in modern organisms9,10. A GRB could have triggered the global cooling, while presenting a host of environmental challenges to life on the planet through the effects of increased radiation reaching the surface, acid rain, etc., followed shortly by global cooling; the result: a one, two punch for life on the planet. Notably, the kind of water depth dependence found in the late Ordovician extinction pattern would emerge naturally from the attenuation of the UV radiation.

29. Predicted as GRB Effects Extinction of shallow (not deep) water organisms Extinction of free-swimming organisms Extinction of surface floaters (plankton) and organisms with planktonic larval forms Nitric acid rain Reduction of solar radiation – cooling Observed in late Ordovician Yes Yes Yes Productivity oscillation in biosphere possibly related to nitrate boost Yes – glaciation needed “kick”

30. Thomas, et al, Conclusions We have no smoking gun. • A strong GRB irradiation of the Earth is probable during the time interval since O2-enrichment of the atmosphere. • Such an event would destroy the ozone layer, exposing organisms to dangerous levels of solar UV. • At least one mass extinction shows characteristics compatible with GRB effects. (astro-ph/0309415)

31. References 1. Mészáros, P. Gamma-ray Bursts: Accumulating Afterglow Implications, Progenitor Clues, and Prospects. Science 291, 79-84 (2001). 2. Thorsett, S.E. Terrestrial Implications of Cosmological Gamma-Ray Burst Models. Astrophys. J. 444, L53-L55 (1995). 3. Scalo, J. & Wheeler, J.C. Astrophysical and Astrobiolgical Implications of Gamma-ray Burst Properties. Astrophys. J. 566, 723-737 (2002). 4. Dar, A. & DeRújula, A. The Threat to Life from Eta Carinae and Gamma-Ray Bursts. in Astrophysics and Gamma Ray Physics in Space (eds. A. Morselli and P. Picozza), Frascati Physics Series XXIV, 513-515 (2002). 5. Weinberg, N., Graziani, C., Lamb, D.Q., & Reichart, D.E. Determining the gamma-ray burst rate as a function of redshift. astro-ph/0210435, to appear in Gamma-Ray Burst and Afterglow Astronomy 2001, proceedings of the Woods Hole, MA symposium. 6. Smith, D.S., Scalo, J., & Wheeler, J.C. Importance of Biologically Active Aurora-like Ultraviolet Emission. Origins of Life and Evolution of the Biosphere, in press, astro-ph/0307543 (2003). 7. Gehrels, N., Laird, C.M., Jackman, C.H., Cannizzo, J.K., Mattson, B.J., & Chen, W. Ozone Depletion from Nearby Supernovae. Astrophys. J. 585, 1169-1176 (2003). 8. Reid, G.C., McAfee, J.R., & Crutzen, P.J. Effects of intense stratospheric ionization events. Nature 275, 489-492 (1978). 9. Kiesecker, J.M., Blaustein, A.R., & Belden, L.K. Complex causes of amphibian population declines. Nature 410, 681-684 (2001). 10. Häder, D., Kumar, H.D., Smith, R.C., & Worrest, R. Aquatic ecosystems: effects of solar ultraviolet radiation and interactions with other climatic change factors. Photochem. Photobiol. Sci. 2, 39-50 (2003).

32. References 11. Sommer, R., Cabaj, A., Sandu, T. & Lhotsky, M. Measurement of UV radiation using suspensions of microorganisms. J. Photochem. Photobiol. B. 53, 1-6 (1999). 12. Brenchley, P.J., et al. Bathymetric and isotopic evidence for a short-lived late Ordovician glaciation in a greenhouse period. Geology 22, 295-298 (1994) 13. Brenchley, P.J., Carden, G.A.F., & Marshall, J.D. 1995, Environmental changes associated with the 'first strike' of the late Ordovician mass extinction. Modern Geology 20, 69-82 (1995) 14. Droser, M.L., Fortey, R.A., & Li, X. The Ordovician radiation. American Scientist 84, 122-131 (1996). 15. Chatterton, B.D.E., & Speyer, S.E. 1989, Larval Ecology, Life History Strategies, and Patterns of Extinction and Survivorship Among Ordovician Trilobites. Paleobiology 15, 118-132 (1989). 16. Scheltema, R.S. Dispersal of marine invertebrate organisms: paleobiogeographic and biostratigraphic implications. (E.G. Kauffman and J.E. Hazel, eds). Concepts and Methods of Biostratigraphy. Dowden, Hutchinson and Ross, Stroudsburg, PA, 73-119 (1977). 17. Orth, C.J., Gilmore, J.S., Quintana, L.R., & Sheehan., P.M. Terminal Ordovician extinction: geochemical analysis of the Ordovician-Silurian boundary, Anticosti Island, Quebec. Geology 14, 433-436 (1986). 18. Herrmann, A.D., & Patzkowsky, M.E. Modeling Response of the Late Ordovician Climate System to Different Forcing Factors. Astrobiology 2, 560-561 (2002). 19.. Berner, R.A., Beerling, D.J., Dudley, R., Robinson, J.M., & Wildman, R.A. Phanerozoic Atmospheric Oxygen. Ann. Rev. Earth Planet. Sci. 31, 105-134 (2003).

33. A More Radical View May Be Emerging Eta Carinae, 700 Lt Yrs away and ready to blow! Beaming factor: 340? 10,000? Not simple in or out of beam, may be nearer or farther from axis.

34. Dar and deRujula GRB Model • Narrow beam confined over galactic distances. • Evidence from TeV observations that most radiation at high energies. • from 2kpc • Equivalent to 1 kiloton TNT / km2over surface, and clearly kills everything. Astro-ph/0110162

35. The End May be in Sight! • There are cosmic hazards to life on earth. • We may have experienced them in the past. • Could explain lack of evident life in galaxy. • Some of these WILL happen, and we shall have to leave earth eventually. • But for now, everything is fine, is fine, is fine….