Download Supernova

Supernova
Type 1 Supernova
Produced in a binary system containing a white dwarf.
The mechanism is the same (?) as what produces the nova event.
Nova
Nova – Rapid increase in luminosity of a white dwarf in a binary system
Rotation
Accretion disc – material pulled into the Roche lobe of the white dwarf
which is eventually deposited on the surface of the white dwarf.
Supernova
TWO VERY DIFFERENT TYPES OF SUPERNOVAE
Supernova Type
Type Ia*
Type II
Maximum Luminosity
3 x 109 Suns
3 x 108 Suns
Spectrum
No hydrogen lines
Lines of many heavy elements
Hydrogen lines
Continuum
Where found
Among old star systems
(galactic bulge, elliptical
galaxies)
Among young star systems
(star-forming regions in disk
galaxies)
Parent Star
White dwarf in binary system
Massive star (usually a red
supergiant)
Trigger mechanism
Mass transfer from companion
Collapse of iron core
Explosion mechanism
Thermonuclear explosion of
carbon/oxygen core --> iron
Rebound shock from neutron
star surface: neutrino pressure
Left behind
Nothing
Neutron star
Debris
Mostly iron
All kinds of elements
*Types Ib and Ic supernovae are unusual supernovae that have most of the properties of type II
supernovae, except that their spectra show no hydrogen lines.
Supernova
Type 1 Supernova
Occurs when the mass of the white dwarf reaches 1.4 M
Recall – the white dwarf is supported by electron degeneracy pressure.
If the accreted mass goes above this value, electron degeneracy pressure cannot
support the inward gravitational pull.
The core will contract and heat up until carbon will fuse rapidly and explosively.
Chandrasekhar Mass – The mass required to drive carbon fusion (equal to 1.4 M)
Supernova
Type 1 Supernova
Carbon-Detonation Supernova – Supernova produced by the rapid fusion
of carbon in a white dwarf.
In looking at the spectra of the supernova remnants, very little hydrogen
spectra is observed.
This might or might not make sense, because the white dwarf has little
hydrogen to begin with, but the companion star has hydrogen.
Supernova
Type 1 Supernova
Type 1 Supernova – the violent explosion of energy triggered by carbon/oxygen
fusion in the core of a white dwarf in a binary system. It is generated by the
accretion of hydrogen from the companion star.
The Type 1 Supernova event is not completely understood
Current thinking A – Type 1 Supernova occur only if all of the hydrogen in the
outer shells of the companion is transferred to the surface of the dwarf.
Helium will then begin to accrete on the surface of the dwarf. Helium requires
much higher temperature to fuse, and this higher temperature explosive
fusion might be enough to drive the core to rapid carbon/oxygen fusion.
When the surface layer explodes, the explosion can be violent enough to
raise the core temperature above the 7 x 108 K required for the fusion of the
carbon/oxygen core of the white dwarf.
The carbon/oxygen fuse explosively, blowing the entire system into space
and leaving nothing behind.
Supernova
Type 1 Supernova
Type 1 Supernova – the violent explosion of energy triggered by
carbon/oxygen fusion in the core of a white dwarf in a binary system. It is
generated by the accretion of hydrogen from the companion star.
The Type 1 Supernova event is not completely
understood
Current thinking B – Once the Chandrasekhar limit is reached, electron
degeneracy pressure can no longer support the strong gravitational
pull, the temperature will rise, and carbon will fuse explosively in the
dwarf.
The carbon/oxygen fuse explosively, blowing the entire system into
space and leaving nothing behind.
Supernova
Type 1 Supernova
Type 1 Supernova – the violent explosion of energy triggered by carbon/oxygen
fusion in the core of a white dwarf in a binary system. It is generated by the
accretion of hydrogen from the companion star.
The Type 1 Supernova event is not completely understood
Current thinking C – The lack of hydrogen in the spectrum of the remnants
suggests that the Type 1 event happens after the companion has been
reduced to a white dwarf.
The two might collide and form one star, which will collapse due to its mass
and cause the carbon-detonation supernova.
The carbon/oxygen fuse explosively, blowing the entire system into space
and leaving nothing behind.