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Cosmic Fireworks:Supernova Explosions
Dr. Stephen C. Y. NgDepartment of Physics
超新星
Outline
Why study supernova?
What is a supernova?
Why does it explode?
The aftermaths --- Supernova remnants
Will it destroy the Earth?
Where do they come from?
Mines?
Supernova Explosions!
Supernova Explosions!
Gold, Silver & More
Heavy Elements
Building Blocks of Life
Life from Exploding Stars!
Without supernovae to disperse elements made in stars, no planets, no life!!
Why Study Supernova?They are cool
most powerful explosions in the Universe
1017J 1044J1,000,000,000,000,000,000,000,000,000 =
Why Study Supernova?
They are importantproduce heavy elements beyond iron, e.g. gold,
silver,…recycle materials into space, e.g carbon, oxygen,
…shock wave triggers new star formation
They can get you a Nobel prizeSN Type Ia as standard candles for cosmology
They are bombsshock wave physics
They are coolmost powerful explosions in the Universe
What is a Supernova?Nova 新星 = new star
Supernova 超新星
Naming:
SN 2013A,…, SN2013Z, SN
2013aa,…
SN 2013ab,…, SN 2013ej,…
Death of a star, most powerful
explosion:1027 nuclear bombs
brighter than a galaxy (~1011 stars)
more energy than the entire lifetime of a star
SN 1994D
Historical ClassificationSN
no H H
Si no Si
He no He
Type Ia Type Ib Type Ic Type II
Physical Classification
Thermonuclear
Core Collapse
SN
no H H
Si no Si
He no He
Type Ia Type Ib Type Ic Type II
Why do they explode?Stellar evolutionCore collapseThermonuclear
Life of a Sun-like Star
Protostars
White Dwarf
Planetary Nebula
Red Giant
Sun-like Star
Star-Forming Nebula
Life of a Massive Star
Protostars
Black Hole
SUPERNOVA
Red Supergiant
Massive Star
Star-Forming Nebula
Neutron Star
self gravit
y
Pressure Balance
self gravit
y
2,000,000,000xin 1 second!
Pressure Balance
self gravit
y
gas pressure
Pressure Balance
Stellar Alchemy
Life of a Sun-like Star
Protostars
White Dwarf
Planetary Nebula
Red Giant
Sun-like Star
Star-Forming Nebula
Massive Stars
Stellar Onion
Inert Iron Core
Stellar Onion
not to scale
self gravit
y
gas pressure
Core Collapse
nuclear force
Core Bounce
Core Bounce
energy: 1046J99% neutrinos1% kinetic energy0.01% visible light
produce heavy elements
recycle light elements
triggers new star formation
Compact Core
Physical Classification
Thermonuclear
Core Collapse
SN
no H H
Si no Si
He no He
Type Ia Type Ib Type Ic Type II
How about SN Type Ia?
White Dwarf
Main Ingredient: White Dwarf
Mass Transfer
Accreting White Dwarf
Binary Merger
Standard Candles
Standard Candles
When can I see a Supernova?
• Expect 1–2/century in our Galaxy, but long
overdue:
Cassiopeia A (~1680AD):peak magnitude = 6?too faint to see
G1.9+0.3 (~1868AD): not visible on Earth, too
far and obscured
SN 1054
• 1054AD July 4
• Crab Nebula (Messier 1)
Crab Nebula• Remnant of SN1054
• Harbors the Crab Pulsar --- most energetic neutron
star found in the Milky Way
Historical Supernovae
Tycho’s SN•1572AD November
•as bright as Venus
•visible until 1574
SN 1006•1006AD May 1•brightest SN observed
•visible for ~18months
Kepler’s SN•1604AD October 9
•visible in day time for 3 weeks
Can I See One Now?• Catch one in the act? Go extragalactic!
• As of today, 6000+ extragalactic SNe observed
Extragalactic SNe
SN 2004et in NGC 6946
SN 1994D in NGC 4526
SN 2013ej in M74
Taken here in HKU
SN 1987A
SN 1987A• 1987 Feb 23, in the Large Magellanic Cloud
• closest (hence brightest) SN observed in 300 yr, since invention of modern telescope
• ~11 neutrinos detected, 3 hr prior to visible light
• complex environment
Milky Way
LMC
SMC168,0
00 light y
ear
Observations
Australia Telescope Compact Array
Chandra X-ray Observatory
Optical X-ray Radio
Evolution
Expansion
35,000 km/s
4000 km/s
Next Supernova in Our GalaxyA major event will be observed by every
telescopes in all wavelengths
radio, IR, optical, X-ray, -ray,...
Multimessenger astronomy beyond EM radiationneutrino telescopesgravitational wave detectors
~100,000 light years across
Artist’s Conception of our Milky Way Galaxy
Will it destroy the Earth?
location of our solar system
Nearest candidate (IK Pegasi): over 150 light years away!
Supernova: within 30 light years
SummarySupernovae are important:
produce everything on Earth
Explosion mechanisms:
core collapse of massive stars
thermonuclear detonations of white dwarfs
The next supernova?
we are safe
SNR G292.2-0.5
Triple-ring Structure
Triple Ring Nebula
Morris & Podsiadlowski (2007)
