an introduction to supernovae - obspm.fr

An IntroductionAn Introductionto to

SupernovaeSupernovae Ewald MüllerMax-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!

Cassiopeia A: Remnant of a supernova exploded around 1680

C h a n d ra : X -ra y c o m p o s ite im a g eX-ray images in differentlines (Si, Ca & FeK)central X-ray

point sourcefound in 2000 by Chandra: a neutron star?

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

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• 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•

• Number of observed extragalactic supernovae: > 3100 (since 1885)

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Supernova 1987A7:35 UT 23.2.1987

Blue SupergiantSandulek 69.202

30 Doradus region in the Large Magellanic Cloud (d ~ 160 000 light years)

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Supernova 1987A

environment & ring system

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Supernova 1987A: Blast wave encountering the inner ring

ROSAT X-ray image of

Vela (d ~500pc) & Puppis (d~2kpc)

SNR

Age of Vela SNR ~11000 yrs

angular size: ~ 8o (ie. ~16 x size of moon)

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 protrusionscredit: Aschenbach et.al 1995, Nature 373, 587

CANDRA X-ray image of immediate neighbourhoodof 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 (2nd time in history!)

ejecta too rich in He & bizarre light curve

--> binary system?

Site of SN 1993J

credit: ESA & J.R.Maund

INT, LaPalma

HST WFPC2

HST ACS/HRC

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 56Ni 56Co 56Fe)

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)

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● Observational facts

● - very bright event: L ~ 1010 Lsun

● - fast expanding ejecta: v ~ 104 km/s ● - energies: electromagnetic: ~ 1049 erg ● kinetic: ~ 1051 erg ● neutrinos (SN1987A): ~ 3 1053 erg (not SNe Ia)

● - progenitor star distroyed (SN 1987A, SN 1993J)

● - freshly synthesized 56Ni (0.07Msun

in SN1987A;

0.2 – 0.8 Msun

in SNe Ia)

● - neutron stars in (some) SNRs (not SNe Ia) ● - neutron star kicks (up to 1000km/s !)

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• energy sources for a supernova explosion

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• thermonuclear energy (SNe Ia)

• conversion of ~1 solar mass of He, C or O into

• iron group nuclei -->

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• gravitational binding energy (SNe II, Ib, Ic)

• formation of a compact object of ~1 solar mass with a radius ~10km

• -->

• E ~ 1051erg

• E ~ 3 1053 erg

Supernova classification according to physical processes

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• Importance of Supernovae:

• Universal players in“

• - nucleosynthesis (we are star dust)

• - star formation (including the solar system)

• - evolution of the ISM (energizing, mixing, ejection)

• - production of cosmic rays (up to 30% of SN energy)

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Si

O

C

He

H

Onion-like structureof a CCSN progenitorseveral million yearsafter its birth:

mass: 10 ... 102 Msun

radius: 50 ... 103 Rsun

- shells of different composition are separated by active thermonuclear burning shells

- core Si-burning leads to formation of central iron core

Note: figure not drawn to scale!

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• Observational evidence for large scale mixing in SN 1987A

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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)●

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Vela SNR: protrusions, fast pulsar

● progenitor: super giant in compact star cluster (Sandage's star 96), ~12 Msol (Wang et al. '05)

30 000 000 km

Blue Giant (Red Giant: × 100)

× 20 000

1500 km

Fe-Ni core

× 100

15 km

Neutron star

Observing the Surface: CCSN length scale problem

● 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 )● ●

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● 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 )● ●

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● 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 ~1021 operations / simulation● or ~1CPU-yr @ 30 Teraflop / simulation)● ●

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Gravitational radiation

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- 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

• □hT Tjk = 0 ( hT T

jk is analogue of vector potential Ai

in electrodynamics )

Gravitational radiation

- leading-order EM multipole radiation from a non-relativistic charge distribution is dipole radiation

- leading-order GW multipole radiation from a mass-energy distribution is quadrupole radiation

A jt ,x =1crd jt− rc

h jkTTt ,x =

2rG

c4Q jkTT t−rc

• (Lorentz-gauge vector potential in wave zone; r ≡ |x| ; dj: electric dipole moment)

• (transverse-traceless-gauge; Qjk: mass quadrupole moment)

Einstein quadrupole formula

(valid for slow motion v«c and weak fields « c2)

Rs=1 km , v/c=0.1 , R=10kpc ---> h ~ 10-20

GW luminosity

h jk=2G

c41RQjk ~

RsR vc

2

LGW=dEGWdt

=15G

c5⟨ Qjk

2⟩ ~ RSR

2

vc 6

Q~MR2/T2~Mv2