1. Supernova Type 2 Supernova Produced during the death of a very massive star.

2. Supernova TWO VERY DIFFERENT TYPES OF SUPERNOVAE Supernova Type Type Ia* Type II Maximum Luminosity 3 x 10 9 Suns 3 x 10 8 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.

3. 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

4. Supernova Type 2 Supernova Burning rates for very massive star of mass about 20 solar masses Element Time to Fuse Hydrogen10 million years Helium1 million years Carbon1 thousand years Oxygen1 year Siliconone week Iron coreForms in less than 1 day.

5. 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.

6. Supernova Type 2 Supernova Iron Core Gravity

7. Supernova Type 2 Supernova Gravity Iron Core – pressure loss from interior (no radiation pressure)

8. Supernova Type 2 Supernova Gravity Iron Core – pressure loss from interior (no radiation pressure)

9. Supernova Type 2 Supernova Gravity Iron Core – pressure loss from interior (no radiation pressure)

10. 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.

11. 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.

12. Supernova Neutron Degeneracy Pressure p + e  n +  When the density of the core is high enough (10 12 kg/m 3 ), 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.

13. Supernova Neutron Degeneracy Pressure p + e  n +  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.

14. Supernova Neutron Degeneracy Pressure p + e  n +  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.

15. Supernova Neutron Degeneracy Pressure p + e  n +  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.

16. Supernova Type 2 Supernova Gravity Iron Core – degeneracy pressure

17. Supernova Type 2 Supernova Gravity Iron Core – degeneracy pressure

18. Supernova Type 2 Supernova Gravity Iron Core – degeneracy pressure

19. Supernova Type 2 Supernova Gravity Iron Core – degeneracy pressure

20. Supernova Type 2 Supernova The inner shell will “rebound” off of the degenerate core

21. Supernova Type 2 Supernova The inner shell will “rebound” off of the degenerate core Pushing outward on the collapsing outer shells

22. Supernova Type 2 Supernova

23. Supernova Type 2 Supernova

24. Supernova Type 2 Supernova The inner shell will “rebound” off of the degenerate core Pushing outward on the collapsing outer shells Until….

25. Supernova Type 2 Supernova

26. Supernova Type 2 Supernova

27. Supernova Type 2 Supernova Kablooey

28. Supernova Type 2 Supernova

29. Supernova Type 2 Supernova

30. Supernova Type 2 Supernova

31. Supernova Type 2 Supernova

32. Supernova Type 2 Supernova

33. Supernova Type 2 Supernova

34. Supernova Type 2 Supernova

35. Supernova Type 2 Supernova Neutron Star: The neutron rich remnant of a Type II Supernova. It is in equilibrium due to neutron degeneracy pressure.

36. 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 CatalogCrab Nebula (M1)Messier Catalog

37. 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.supernovaSN1987ALarge Magellanic CloudHubble Space Telescope

38. 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.Eta Carinae Supernova Type 2 Supernova