cosmic fireworks: supernova explosions

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)