Download When Stars Attack! In Search of Killer Supernovae

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
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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
:
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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