2. Supernova Supernova! (And other Cataclysmic Events!)

4. What’s in a name Historical Supernovae Types of Supernova Where do they go? Really wild Explosions Can I see a Supernova? Introduction

5. Nova Nova - Latin for New Star Faint star that suddenly brightens Supernova! A bright star that explodes Can be as bright as an entire galaxy Hypernova Appears to be as bright as the rest of the Universe

6. Early Supernova Reports Supernovae can be visible in daylight Many Chinese reports of “Guest Stars” Rock Drawings?

7. Chaco Canyon - SN1054??

8. Milky Way Supernovae Year Date Con RA Dec mag Comment 185 AD Cen 14:43.1 -62:28 -2 -6 mag 393/396 Sco 17:14 -39.8 -3 1006 Apr 30 Lup 15:02.8 -41:57 -9 1054 Jul 4 Tau 05:34.5 +22:01 -6 M1 1181 Cas 02:05.6 +64:49 -1 1572 Nov 6 Cas 00:25.3 +64:09 -4 Tycho 1604 Oct 9 Oph 17:30.6 -21:29 -3 Kepler 1667? Cas 23:23.4 +58:50 6? Cas A SN

9. SN1987A BeforeAfter

10. Supernova Types Type 1 Type 2 There are various subclasses Defined by their Spectra and Lightcurves

11. The Spectrum

12. Types of Spectrum

13. Spectra of Elements Hydrogen Helium Carbon

14. Solar Spectrum

15. Type 1 Supernova

16. Type II Supernova

17. Lightcurve Comparison

18. Supernova Mechanisms Basic Stellar Structure Type II Supernovae Type I Supernovae

19. What is a Star? A sphere of gas in hydrostatic equilibrium

21. What is a Star? A sphere of gas in hydrostatic equilibrium Nuclear Fusion within the sphere

24. What is a Star? A sphere of gas in hydrostatic equilibrium Nuclear Fusion within the sphere Emits energy as radiation and particles Varies in size and brightness over its lifetime

29. Helium Burning

32. Timescales

33. But…! Iron won’t “burn” and release energy No energy from the core holding up the outer layers The core collapses to about 10Km diameter Protons and electrons are squeezed together to form neutrons and releasing neutrinos Neutrinos escape speeding up the collapse

34. … And... Infalling material rebounds off the core Shockwave travels outwards compressing and heating surrounding gas Remainder of the star blasted out Energy released is about the same as the Sun will generate in its entire life! Supernova!! (Type II)

38. Type II Supernova

39. Type 1 Supernova

40. Type I Supernova Mechanism Form in Binary Systems Gas falls from a Red Giant onto a White Dwarf

42. Type I Supernova Mechanism Form in Binary Systems Gas falls from a Red Giant onto a White Dwarf Gas forms on the surface of the White Dwarf

44. Type I Supernova Mechanism Form in Binary Systems Gas falls from a Red Giant onto a White Dwarf Gas forms on the surface of the White Dwarf Mass Exceeds stability limit (Chandarasekar Limit - 1.4 M sun )

45. Type I Supernova Mechanism Core collapses Carbon Core ignites explosively Supernova! Always happens at the same Mass Limit Gives out (nearly!) the same amount of energy Can be used as a “Standard Candle”

46. Type I Sn Standard Candle Allows us to measure distance to very remote galaxies Remote Galaxies are a long way back in time Allows us to measure changes in the rate of Cosmic expansion Expansion is speeding up!!

47. While we’re here.. “Classical Nova” mechanism is very similar to Type I Supernova Gas accretes in a binary system Layer of hydrogen forms around the white dwarf (about 1/100,000 M sun ) Hydrogen ignites as a shell around the White Dwarf

49. While we’re here.. “Classical Nova” mechanism is very similar to Type I Supernova Gas accretes in a binary system Layer of hydrogen forms around the white dwarf (about 1/100,000 M sun ) Hydrogen ignites as a shell around the White Dwarf … and ejects the surrounding Hydrogen as a Planetary Nebula

51. What Happens Next? Type II Supernova core forms a Neutron Star Surrounding material ejected by the shockwave

52. Neutron Stars Type II Supernova core forms a Neutron Star ~ 10Km in diameter Incredibly dense - 200,000,000 tons / cc Spins very fast and has a very powerful magnetic field

53. Conservation of Angular Momentum

54. Conservation of Magnetic Flux The star’s magnetic field collapses Magnetic field density increases to about 10 12 Gauss Magnetic poles may not be aligned with rotational poles Produces the Pulsar Lighthouse Effect

57. Pulsar Radiation Detailed mechanism not really understood Probably caused by the intensely curved fields around the magnetic poles Electrons in a curved magnetic field emit radiation Highly directed in two beams

58. Pulsar Discovery First detected in Cambridge in 1967 by Jocelyn Bell Burnell and Anthony Hewish Initial discoveries were called LGM

59. Fast and Slow Pulsars Periods can range from a few seconds to milliseconds They slow down over time but are highly accurate over normal timescales Binary Pulsar has been used to prove the theory of Relativity Pulsars were used on the Voyager plaque to pinpoint the Earth

62. Crab Pulsar

65. Nucleosynthesis Lighter elements are created by fusion

67. Nucleosynthesis Lighter elements are created by fusion Heavy elements are created by nuclear reactions –s-process (Slow Neutron Capture) –r-process (Rapid Neutron Capture) –p-process (Proton Capture)

68. Where do we come from? All elements heavier than Helium were created in previous generations of Supernovae

69. Where do we come from? All elements heavier than Helium were created in previous generations of Supernovae “We are Stardust”

70. Some Very Big Explosions Stars below about 8 M sun won’t go Supernova, including our sun Very massive stars will blow off gas during their lifetime

72. Some Very Big Explosions Stars below about 8 M sun won’t go Supernova, including our sun Very massive stars will blow off gas during their lifetime Core of a star > 25 M sun is too massive to be held up by Neutron degeneracy and will collapse to a Black Hole about 20Km wide

73. Gamma Ray Bursters GRBs Found by spy satellites and thought to be nuclear tests in space! Originally thought to be Milky Way objects Now identified with very intense explosions in external galaxies Hypernova

74. Hypernovae Energy flux if isotropic would be immense, about the same as the rest of the universe for a few seconds Likely to be a directed beam effect like Pulsars No-one is sure but there are a number of theories

75. Collapse of Magnetic Star ~ 40 M sun Very massive star with strong magnetic field collapses to a Black Hole

76. Collapse of Magnetic Star ~ 40 M sun

77. Very massive star with strong magnetic field collapses to a Black Hole Matter ejected at near the speed of light Matter is constrained by magnetic field into jets at the poles Relativistic effects include beaming of energy in the direction of travel

79. Neutron Star Merge

81. Hypernovae There do appear to be 2 classes of GRBs so both theories may be right About 1 GRB detected per day but we only see those where the beam is directed at us Frequency much higher in the early universe than now A local GRB pointed at Earth would essentially cook that hemisphere!

82. Observing a Supernova One in the Milky Way every 250 years Last one in 1667, so we’re overdue one! Sn1987A in the LMC (our nearest neighbour galaxy) Can be observed in external galaxies Hundreds have been discovered by amateurs

84. SN2002ap

85. SN2002cs

89. Stop Press!

90. Summary There are various types of exploding stars Novae, Supernovae (types I & II), GRBs Large to huge amounts of energy released Produce all heavy elements They are observable with amateur equipment

91. Some Resources http://skyandtelescope.com http://www.supernovae.net http://www.theastronomer.org http://www-astronomy.mps.ohio- state.edu/~dhw/Intro/current.html#lectures http://www.pas.rochester.edu/~afrank/A105 /index.html