An Introduction to Supernovae - LUTH

An Introduction
to
Supernovae
Ewald Müller
Max-Planck Institut für Astrophysik

E S O -V LT
Crab nebula
with pulsar
(constellation
Orion)
Remnant of a
supernova
observed in
the year 1054

A New Star, as bright and as red as
Mars, was discovered on October 9
1604, close to the position where
another astrologically significant event
was taking place, the conjunction of
Mars and Jupiter. The New Star created
a stir throughout Europe.
At Padua the new star was observed by
Galileo, while in Prague Kepler made
careful observations and the Supernova
now carries his name.
Galileo gave 3 public lectures that were
attended by a large audience in which
he demonstrated that the new star was
much further than the moon.
This had important astronomical
consequences since it showed that
change occurrs in the sky, contrary to
the theory of Aristotle and his followers.

SN 1604 composite image:
X-ray (Chandra, green-blue)
optical (HST, yellow)
IR (SST, red)
Last observed galactic
supernova!
Note:
first use of a telescope for
astronomical purpose by
Galileo Galilei in 1609!

C h a n d ra : X -ra y c o m p o s ite im a g e
central X-ray
point source
found in 2000
by Chandra: a
neutron star?
Cassiopeia A:
Remnant of a supernova
exploded around 1680
X-ray images
in different
lines
(Si, Ca & FeK)

Cas A composite image:
X-ray (Chandra, green-blue), optical (HST, yellow) & IR (SST, red)

•
• Supernovae in the Milky Way during the last millenium
•
• date visible for distance observed in/by
• 1006 some years 6 500 far east, Arabia, St.Gallen
• 1054 about 2 years 7 100 far east, Arabia
• 1181 6 months 26 000 China, Japan
• ~1300 ? 650 ? (RX J0852-4642)
• 1572 16 months 23 000 Tycho Brahe
• 1604 about 1 year 32 000 Johannes Kepler
• ~1680 ? 11 000 Flamsted ? (Cas A)
• 23.2.1987 >18 years 160 000 Ian Shelton
•
1
• Number of observed extragalactic supernovae: > 3100 (since 1885)

30 Doradus region in the Large Magellanic Cloud
(d ~ 160 000 light years)
-
Blue Supergiant
Sandulek 69.202
Supernova 1987A
7:35 UT 23.2.1987

-
Supernova 1987A
environment & ring system

Supernova 1987A: Blast wave encountering the inner ring
-

angular size: ~ 8 o (ie. ~16 x size of moon)
ROSAT X-ray
image of
Vela (d ~500pc)
&
Puppis (d~2kpc)
SNR
Age of Vela SNR
~11000 yrs
credit:
Aschenbach et.al
1995, Nature 373, 587

ROSAT X-ray observations at
low energy & high energy
reveal three (!) partially overlapping SNRs:
Vela, Puppis A & Vela Jr. (RX J0852.0-4622)
(Aschenbach 1998, Nature 396, 141)

credit:
W.P.Blair
(John Hopkins Univ.,
Baltimore, USA)

ROSAT X-ray picture with
labeled protrusions
credit: Aschenbach et.al
1995, Nature 373, 587
CANDRA X-ray image of
immediate neighbourhood
of Vela pulsar
(region would be barely visible
on neigbouring ROSAT image!)

ESO-VLT: NGC 6118 & SN2004dk
( d ~ 25 Mpc , Ib/c)

SN 1993J in M81: Evolution of the radio remnant (MERLIN)

SN 1993J in M81
(d = 3.7 Mpc)
Evolution of the radio
remnant (MERLIN)
* March 28, 1997
red supergiant
progenitor identified
(2 nd time in history!)
ejecta too rich in He &
bizarre light curve
--> binary system?

INT, LaPalma
HST WFPC2
HST ACS/HRC
Site of SN 1993J
credit:
ESA & J.R.Maund

Close-up of SN 1993J explosion site
blue companion star
discovered 10 years after
explosion by HST
light echo
(credit: ESA & J.R.Maund)

SN 1993J exploding (artist's impression)
[ credit: ESA & J.R.Maund ]

T y p e Ia s u p e rn o va a t z = 0.9 5

Supernova „botanics“ according to spectra & light curves

Supernova light curves
pronounced maximum
after 2-3 weeks
exponential tail
(radioactive decay of
56 Ni 56 Co 56 Fe)
maximum brightness
largest for SNe Ia
only SNe Ia form a (quite)
homogeneous class
standard candles!?
possibility to measure
expansion of universe

Supernova spectra
discriminate types
(no spectrum no type!!)
provide information
about
- stellar & explosive
nucleosynthesis
- abundances and
chemical stratification
(tomography)
- stellar environment &
progenitor star

Number of supernovae per year as function of survey distance
Milky way: 2.4 supernovae/century (70% CCSN) (Arnaud etal '04)
(none in Milky way since 1680 & none in Andromeda since 1885)

●
● Observational facts
● - very bright event: L ~ 10 10 L sun
● - fast expanding ejecta: v ~ 10 4 km/s
● - energies: electromagnetic: ~ 10 49 erg
● kinetic: ~ 10 51 erg
● neutrinos (SN1987A): ~ 3 10 53 erg (not SNe Ia)
● - progenitor star distroyed (SN 1987A, SN 1993J)
● - freshly synthesized 56 Ni (0.07M sun in SN1987A;
0.2 – 0.8 M sun in SNe Ia)
● - neutron stars in (some) SNRs (not SNe Ia)
● - neutron star kicks (up to 1000km/s !)

•
• energy sources for a supernova explosion
•
• thermonuclear energy (SNe Ia)
• conversion of ~1 solar mass of He, C or O into
• iron group nuclei -->
•
• gravitational binding energy (SNe II, Ib, Ic)
• formation of a compact object of ~1 solar mass
with a radius ~10km
• -->
• E ~ 3 10 53 erg
• E ~ 10 51 erg

Supernova classification according to physical processes

•
•
• Importance of Supernovae:
• Universal players in“
• - nucleosynthesis
(we are star dust)
1
• - star formation
(including the solar system)
• - evolution of the ISM
(energizing, mixing, ejection)
• - production of cosmic rays
(up to 30% of SN energy)

●
●
Si
O
Note: figure not drawn to scale!
C
He
H
Onion-like structure
of a CCSN progenitor
several million years
after its birth:
mass: 10 ... 10 2 M sun
radius: 50 ... 10 3 R sun
- shells of different
composition are
separated by active
thermonuclear
burning shells
- core Si-burning
leads to formation
of central iron core

•
• Observational evidence for large scale mixing in SN 1987A
1

Observational evidence for a globally anisotropic explosion
●SN1987A:
●ejecta are non-spherical
●
●(Wang et al. 2002)

Further evidence for non-spherical core collapse supernova explosions
● indirect:
● - large pulsar velocities
- association with long GRBs
- asymmetries in late-time emission-line profiles of SNe Ic
● direct:
● - spectropolarimetry of SNe Ic &
● SNe II-P (SN2004dj, 3.1Mpc; Leonhard et al. '06)
●
●
●
●
●
●
●
●
●
●
●
●
Vela SNR:
protrusions, fast pulsar
● progenitor: super giant in compact star cluster (Sandage's star 96), ~12 M sol (Wang et al. '05)

Observing the
Surface:
CCSN length
scale problem
30 000 000 km
15 km
Blue Giant (Red Giant: × 100)
× 20 000
× 100
Neutron star
Fe-Ni core
1500 km

● Looking into the heart of a core collapse supernova
● - through observations of neutrinos
● (up to now only SN1987A)
●
● - th ro u g h o b s e rva tio n s o f g ra vita tio n a l w a ve s
● (n o t y e t o c c u re d ! W o u ld p ro vid e kin d o f R o s e tta s to n e !)
●
● - th ro u g h s im u la tio n s
● (a lre a d y a 4 0 y e a r e ffo rt ; e x tre m e ly c o m p le x &
● e x p e n s ive 6 D ra d ia tio n -h y d ro d y n a m ic s p ro b le m
● re q u irin g ~1 0 21 o p e ra tio n s / s im u la tio n
● o r ~1 C P U -y r @ 3 0 T e ra flo p / s im u la tio n )
●
●
●

● Looking into the heart of a core collapse supernova
● - through observations of neutrinos
● (up to now only SN1987A)
●
● - through observations of gravitational waves
● (not yet occured! Would provide kind of Rosetta stone!)
●
● - th ro u g h s im u la tio n s
● (a lre a d y a 4 0 y e a r e ffo rt ; e x tre m e ly c o m p le x &
● e x p e n s ive 6 D ra d ia tio n -h y d ro d y n a m ic s p ro b le m
● re q u irin g ~1 0 21 o p e ra tio n s / s im u la tio n
● o r ~1 C P U -y r @ 3 0 T e ra flo p / s im u la tio n )
●
●
●

● Looking into the heart of a core collapse supernova
● - through observations of neutrinos
● (up to now only SN1987A)
●
● - through observations of gravitational waves
● (not yet occured! Would provide kind of Rosetta stone!)
●
● - through simulations
● (already a 40 year effort ; extremely complex &
● expensive 6D radiation-hydrodynamics problem
● requiring ~10 21 operations / simulation
● or ~1CPU-yr @ 30 Teraflop / simulation)
●
●
●

•
•
Gravitational radiation
- ripples in the fabric of spacetime (relative to smooth background)
- far from strong gravitational fields (weak gravitation)
g = + h |h | ≪ 1
Minkowski metric + small perturbation
- plug into Einstein field equations --> wave equation
T T
• □h jk
= 0 ( hT T
jk is analogue of vector potential A i
in electrodynamics )

Gravitational radiation
- leading-order EM multipole radiation from a non-relativistic
charge distribution is dipole radiation
A jt ,x= 1
cr ˙d j
r
t−
c
- leading-order GW multipole radiation from a mass-energy
distribution is quadrupole radiation
TT 2
hjk t ,x=
r
TT
G
c 4 ¨Q jk
t− r
c
• (Lorentz-gauge vector potential in
wave zone; r ≡ |x| ;
d j : electric dipole moment)
• (transverse-traceless-gauge;
Q jk : mass quadrupole moment)

Einstein quadrupole formula
(valid for slow motion v«c and weak fields « c 2 )
h jk= 2G
c 4
R s =1 km , v/c=0.1 , R=10kpc ---> h ~ 10 -20
GW luminosity
L GW= d E GW
dt
1
R ¨Q jk ~ R s
R v
c 2
= 1
5
G
c 5 〈 Q jk 2
〉 ~ R S
R 2
v
c 6
¨Q~MR 2 /T 2 ~Mv 2