Transcript The Danger of Deadly Cosmic Explosions

The Danger of Deadly
Cosmic Explosions
John Learned
UH Physics & Astronomy
A736/P711 19 April 2005
Extinctions of Species on Earth
Shows 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?
Later classes have larger brains.
Time difference around 100 million years.
Jim Annis
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.
AGN Jets, Bad but Not Here Soon
M87 at 60MLyr… fortunately not pointing at us.
Does seem to be swinging around though…
Markarian 421
Blazar, pointing at us
Around 360 MLyr away
No danger, but impressive
Supernova Explosions Near Earth
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!
Next 10 slides from B. Fields, edited by jgl
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.”
How Close is Too Close?
Minimum safe distance:
About 30 light years
Note: nearest star is 4 light years
30 light years
Surgeon General’s Warning:
Supernovae are Dangerous to Your Health!
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
The Smoking Gun:
Supernova Debris on the Earth
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
X 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?
Deep Ocean Crust
Measured by German team
ferromanganese (FeMn) crust
Pacific Ocean
growth: ~ 1 mm/Myr
live radioactive iron atoms
60Fe
  2.2 Myr !
a few dozen atoms total (!)
 60Fe found in all layers?
Q: possible explanations?
Amount of radioactive iron
1998
Depth in crust=time deposited
Confirmation
Knie et al (2004)
Advances
•
New crust from new site
•
Better geometry (planar)
better time history
Isolated Signal
t  2.8  0.4 Myr
Amount of radioactive iron
60Fe
A Landmark Result
 Isolated pulse identified
 Epoch quantified
 Consistent with original crust
Woo hoo!
Instrumental “noise”:
60Ni
Depth in crust=time deposited
Note fantastic
AMS sensitivity!
60Fe
&
53Mn
in Deep Ocean Crust
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!
A Near Miss?
d  dkill ...but barely: "near miss"
¿ Climate change from radiation?
¿ bump in extinctions?
If true: implications for astrobiology
tightens Galactic habitable zone
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
Increased Rate at Arm Crossings?
Leitch and Vashist, 1998
Did a Gamma-Ray Burst
initiate the late Ordovician
mass extinction?
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
Next 15 slides from these guys… but edited by jgl.
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.
Terrestrial Consequences
of 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.
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 (>1018
eV) 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!
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.
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 particulates and 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.
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.
Typical Ordovician organisms
www.ucmp.berkeley.edu/ordovician/ordovician.html Image Courtesy
W. Berry, University of California Museum of Paleontology
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.
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.
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.
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
Observed in late
Ordovician
Yes
Yes
Yes
Nitric acid rain
Productivity oscillation in
biosphere possibly related to
nitrate boost
Reduction of solar radiation –
cooling
Yes – glaciation
needed “kick”
Thomas, et al, Conclusions
• A strong GRB irradiation
of the Earth is probable
during the time interval
since O2-enrichment of
the atmosphere.
We have no smoking gun.
• 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)
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, astroph/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).
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).
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.
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 / km2 over surface,
and clearly kills everything.
Astro-ph/0110162
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….