Transcript Type II SuperNova - University of Dayton

Supernova
Type 2 Supernova
Produced during the death of a very massive star.
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 2 Supernova
Late in the life a a
very massive star
(10 or more times
the mass of the sun)
the tiny core of the
star develops a
layered structure
much like an onion,
with heavier and
heavier elements in
deeper layers,
culminating with
iron in the center
See Figure 21.5
Supernova
Type 2 Supernova
Burning rates for very massive star of mass about 20 solar masses
Element
Time to Fuse
Hydrogen
10 million years
Helium
1 million years
Carbon
1 thousand years
Oxygen
1 year
Silicon
one week
Iron core
Forms in less than 1 day.
Supernova
Type 2 Supernova
In very massive stars this situation eventually becomes unstable and the
core of the star collapses catastrophically in a time of only a few
thousandths of a second. This collapse leads to an explosion called a
Type II Supernova that blows off the outer layers of the star and produces
a prodigious light show that can rival the luminosity of an entire galaxy
(billions of normal stars). As spectacular as this is, most of the energy of
the supernova is actually contained in ghostly particles called neutrinos
that are very difficult (but not impossible) to detect. There are other types
of supernovae that involve a somewhat different mechanism associated
with mass accretion by a white dwarf in a binary system, but the final
result is similar: a gigantic explosion that destroys an entire star.
Supernova
Gravity
Type 2 Supernova
Iron Core
Supernova
Gravity
Type 2 Supernova
Iron Core – pressure loss from interior (no radiation pressure)
Supernova
Gravity
Type 2 Supernova
Iron Core – pressure loss from interior (no radiation pressure)
Supernova
Gravity
Type 2 Supernova
Iron Core – pressure loss from interior (no radiation pressure)
Supernova
Type 2 Supernova
The core collapses as a result of the collapse of the outer layers
Electron degeneracy pressure is not enough to stop the gravitational
collapse of the outer shells.
Supernova
Neutron Degeneracy Pressure
Extreme pressures in the core will increase the temperature to
fantastically high numbers (10 billion K). At this temperature, the
energies of photons in the core will be high enough to break the iron
into fundamental particles
Photodisintegration: The process by which the core is broken into
fundamental particles by high energy photons.
Supernova
Neutron Degeneracy Pressure
p+en+ν
When the density of the core is high enough (1012 kg/m3), protons and
electrons will be crushed together, forming neutrons in the core and
releasing neutrinos.
Neutronization: The conversion of the core into neutrons by the
combining of electrons and protons.
Supernova
Neutron Degeneracy Pressure
p+en+ν
The neutronization of the core results in an enormous outflow of neutrinos.
A “large” neutrino flux at the earth is a sign of a
supernova event.
Supernova
Neutron Degeneracy Pressure
p+en+ν
Like electrons, two neutrons cannot be in the same state at the same
time.
Neutron Degeneracy Pressure: Pressure produced when two neutron
are squeezed into a small enough space.
Neutron Degeneracy Pressure is a parallel to electron degeneracy
pressure.
Supernova
Neutron Degeneracy Pressure
p+en+ν
When the pressure is the core is dominated by neutron degeneracy
pressure, the core collapse stops, and the resulting pressure acts a
barrier which stops the further collapse of the outer shells.
The process happens very rapidly, however, and the outer shells cannot
react immediately to the pressure exerted by the core.
Supernova
Gravity
Type 2 Supernova
Neutron Core – degeneracy pressure
Supernova
Gravity
Type 2 Supernova
Neutron Core – degeneracy pressure
Supernova
Gravity
Type 2 Supernova
Neutron Core – degeneracy pressure
Supernova
Gravity
Type 2 Supernova
Neutron Core – degeneracy pressure
Supernova
Type 2 Supernova
The inner shell will “rebound”
off of the degenerate core
Supernova
Type 2 Supernova
The inner shell will “rebound”
off of the degenerate core
Pushing outward on the
collapsing outer shells
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Type 2 Supernova
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Type 2 Supernova
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Type 2 Supernova
The inner shell will “rebound”
off of the degenerate core
Pushing outward on the
collapsing outer shells
Until….
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Type 2 Supernova
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Kablooey
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Type 2 Supernova
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Type 2 Supernova
Neutron Star: The neutron rich remnant of a Type II Supernova. It is in
equilibrium due to neutron degeneracy pressure.
Supernova
Type 2 Supernova
Long after the initial
supernova explosion, its
aftermath can be seen in
the expanding cloud of
debris produced by the
explosion. These are
called Supernova
Remnants. One of the
most famous supernova
remnants is the Crab
Nebula (M1), which is the
remains of the supernova
of 1054 AD that is
chronicled in the Chinese
literature, and is the first
entry in the Messier
Catalog
Supernova
Type 2 Supernova
In 1987 a supernova (designated SN1987A by
astronomers) was observed in a nearby galaxy called
the Large Magellanic Cloud. This was the first "nearby"
supernova in the last 3 centuries, and for the first time
astronomers not only observed the light show, but
also detected 19 of the elusive neutrinos (the detectors
observed electron anti-neutrinos, to be more precise)
produced by the collapse of the star's core. The burst
of neutrinos preceded the first sighting of the
supernova's light by about 3 hours, in agreement with
the expectations of current supernova theory. It is
estimated that for an instant in 1987 on the earth the
neutrino luminosity of SN1987A was as large as the
visible-light luminosity of the entire universe. The
adjacent figure is a 1994 Hubble Space Telescope
image of the region surrounding SN1987A. The
supernova is in the center. The two bright stars are
just in the field of view and are not associated with the
supernova. The bright yellow ring is thought to be gas
and dust heated by the supernova (the expanding shell
of the explosion itself that will produce the supernova
remnant is still too small to be seen in this
photograph). The two large rings are not yet
completely understood, though they appear to be
associated with the supernova.
Supernova
Type 2 Supernova
The supermassive and violently unstable star Eta Carinae. The adjacent
image shows a nebula larger than the Solar System that was ejected in a
violent outburst in 1841. For a time, this outburst made Eta Carinae the
second brightest star in the sky.