1 − – 45) MeV − 3 3 2 / / 75 1 . 1 Z A A ulomb 75 . 2(30 ns and protons +0 ! 2+ 2 » « = Lattimer, AST 301, Supernova/Neutron Star Lecture – p.1/31 Z = 0 − A = 0 opt A ˛ ˛ ˛ ˛ ˛ N « A ) 26 ˛ ˛ ˛ ˛ ˛ „ Z A ≃ Z,A „ 45 Z,A Z/A ( ∂Z opt ∂E − ∂ ∂E , 18 «
, 2 2 3 , Z , / A Z 2 60 5 = 0 . A = 0 1 ≃ + Z „ ˛ ˛ ˛ ˛ ˛ ! Z/A 2 ˛ ˛ ˛ ˛ ˛ opt « A A,Z ! , ∂A Z A,Z 2 ∂A ∂E − A « ∂E Z N „ − A N „ 45 16 + 30 − −
18 A
Type II Supernovae = = The optimum mass and charge for a nucleus happen when Iron has the highest bindingBethe-von energy Weisäcker of mass any formula: nucleus Energy = Bulk + Bulk Symmetry + Surface + Surface Symmetry + Co Symmetry energy comes from having unequal numbers of neutro opt A,Z • A E . ⊙ pse. .4 M e’s outer boundary. uclei has a ar and ejecting g infalling matter. ese beta reactions urn, the iron core mass er core and a inside nuclei is reached, Lattimer, AST 301, Supernova/Neutron Star Lecture – p.2/31 s a new neutron star, m a neutron star in having e ν + n → − e + p
Collapse many more protons and electrons as well as being much hotter. supersonic outer core. The shock slows down or reverses the collapse of the overlyin called a protoneutron star. A protoneutron star differs fro produce neutrinos. In a massive star, the core which has matter burned intoAs iron the n silicon shell surrounding the iron core continues to b When the core exceeds the Chandrasekhar mass,The it collapsing has core to separates colla into a sonically cohesive inn The collapsing core continues to collapse until the density The abrupt halt creates a pressure shock wave at the inner cor This shock by itself does not seem capable of exploding the st The inner core plus additional matter falling onto it create During collapse, some protons are converted to neutrons. Th maximum size determined by the Chandrasekhar limit, about 1 slowly increases. when nuclear repulsive forces abruptly halt the collapse. matter into space. • • • • • • • • • Lattimer, AST 301, Supernova/Neutron Star Lecture – p.3/31 . n it. This happens beta equilibrium) that tion is about Lattimer, AST 301, Supernova/Neutron Star Lecture – p.4/31 , the neutrinos can no R energy into internal and . ρ 0 ergs e N ν 53 = + between collisions with nucleons, 10 n ) n × , about 1000 times less than the final nσ ⇌ 3 3 ( / − ≃ e g/cm 2 = 1 + R d p 12 5 GM − 3 11 10 . 2 is comparable to the stellar radius d cm 2 MeV) / ν is the number density of nucleons E n ( 44 Neutrinos − where neutron star density. 10 prevents more proton conversion. thermal energy in the protoneutron star. Neutrinos interact very weakly with matter. Their cross sec They travel an average distance When the distance The law of mass action then results in an equilibrium (called Gravitational collapse converts gravitational potential This energy is the same as the Sun’s power output over 2500 Gyr longer escape the star and become temporarily trapped withi when the density is about • • • • • • miokande and erg. detected neutrino s way. 49 y is degraded e over which the nter to the surface. cities up to 1% the 10 erg/s. t st enough energy to Lattimer, AST 301, Supernova/Neutron Star Lecture – p.5/31 43 s 10 3 erg. erg. − 51 53 10 ρ 10 g cm · 15 = 9 10 2 ) 10 10 ≃ 10 2 · R cd 3 (3 ∗ = τ 33 10 · 2)2 / = (1 2 c ⊙ M
Explosion 2) / energy was about 20 MeV. The luminosity at peak of a TypeIt II is supernova brightest is for about about a monthThe and outer therefore several radiates solar abou masses of the star are ejected at velo The kinetic energy of the ejected mass is about Where does the rest of the energyNeutrinos go? flowing Neutrino through the emission. outer material can transfer ju The emission of neutrinos was detected from SN 1987A by theThe Ka trapping of neutrinos was confirmed because the timescal The neutrinos in the core’s center is about 300 MeV; the energ speed of light. eject them. Less than 1% of their energy needs to bethe used IMB in detectors. thi neutrino burst appeared was about 10 seconds and the average because of energy losses asThis the diffusion neutrinos takes diffuse time from the ce (1 • • • • • • • • • Lattimer, AST 301, Supernova/Neutron Star Lecture – p.6/31 g. 9 kpc = 10 . = 50 kt = 59 D . 10 2 · ν = 1 ) E d ν of protons in the 44 erage escaping M where utrinos thermalized diated. The number of − /E ) Lattimer, AST 301, Supernova/Neutron Star Lecture – p.7/31 2 10 · 4 πD . )=(2 (4 6 ∼ 32 / MeV, suggesting of order 6 − . ¯ ν σ 10 , measured in MeV, the total 58 10 · ν · σN E 10 = 20 3) 6 p · . / ν 1 N ) / ν E ν = . = (2 ν E /E d ( E / N 3 erg. . neutron star should be about = (3 SN water 53 ⊙ ¯ ν ρ E = 0 d 10 N M d · 4 . M N 1 18) / ) = 3 o N /R 2 = 2( GM p N 5)( / cm. This is about 23 = (3 10
Neutrino Detection · 5 SN . neutrinos should be observed. Neutrino detectors had total detector water massesOnly of the about protons in water could detect neutrinos. The number The energy release from a If the average energy of detected neutrinos is Only anti-electron neutrinos were observed. Because the ne The cross section of the neutrinos withThe protons number is of detected neutrinos is The average observed energy was about The duration of the event, about 10 s, is consistent with an av detectors is due to diffusion, equal numbersanti-electron of neutrions all is neutrino then types were ra energy of 20 MeV. number of radiated neutrinos is 1 E • • • • • • • • • • Although neutrinos carry energy into the outer matter, simulations indicate this is insufficient to eject these layers except in the smallest stars. • Auxiliary energy from rotation, magnetic field compression, or acoustic vibrations have all been suggested to augment neutrino energies. • As for Type Ia supernovae, the complete mechanism is uncertain, and the progenitors are not clearly identified. • From the light curve, it is easy to identify the amount of radioactive 56Ni that is ejected.
SNII,bluegiant SNII,redgiant SNIa
Lattimer, AST 301, Supernova/Neutron Star Lecture – p.8/31 d, compared to can be built by the beta stability. ; they form waiting n-rich nuclei. N clei, but which nuclei Lattimer, AST 301, Supernova/Neutron Star Lecture – p.9/31 ctive nuclei that eventually . Z e ν + ¯ − e + p → n p-process (proton) s-process (slow neutron) r-process (rapid neutron)
Nucleosynthesis Of The Heavy Elements • • • continuous addition of protons or neutrons: beta-decay towards the valley of beta stability. Three basic processes can be identified by which heavy nuclei Capture of protons on light nuclei tendCapture to of produce neutrons only on proto light nuclei produce neutron-rich nu Beta decay: Slow capture path is in and producesRapid nuclei capture near initially the produces valley very of neutron-rich radioa Neutron magic numbers (50,82,126) impede flows to larger Some nuclei can be built by more than one process. are produced depends upon thetypical rate beta-decay at timescales. which neutrons are adde points where beta decays increase • • • • • • • • 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.10/3
Chart Of The Nuclides 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.11/3
Nuclide Chart Portion 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.12/3
Beta Decay Rates 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.13/3
S- and R-Processes Compared 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.14/3 Sneden et al. (2003) an ultra metal-poor halo star [Fe/H]=-3.1 for CS 22892-052,
R-Process In An Old Star 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.15/3
The R-Process Through The Ages 1 , and long per event), e Y onal radiation. ⊙ r or black hole in a M 5 a massive star and − Lattimer, AST 301, Supernova/Neutron Star Lecture – p.16/3 10 or small s ) n, γ ( extremely large , relatively equilibrium. i.e. ) , n/p n, γ n/p ( − ) γ,n ( reactions. per event), early onset in galactic decay ⊙ − M β 01 . 0 Neutrino-driven wind following gravitational collapse of Develops into a Advantages: Higher frequency requires small yield ( Problems: Requires high Tidal disruption of a neutron starcompact merging binary with whose a orbit neutron is sta decaying becauseDevelops into of a gravitati competition between and Advantages: Naturally high robust in terms of initial conditions. Problems: Rarity requires relatively large( yield history requires short orbital decay timescales. formation of proto-neutron star. naturally early onset in cosmic history. duration. • • • • • • • • Traditional (and favorite) source is SN II. Non-standard model is decompressingmatter. neutron star • •
Proposed Astrophysical Sites Goriely 2005
Lattimer, AST 301, Supernova/Neutron Star Lecture – p.17/31 1 293 MeV . 78 . 0 = 1 ≃ 2 c 3 7 + . . ) e Lattimer, AST 301, Supernova/Neutron Star Lecture – p.18/3 7 5 p + m ≃ n − p n n → ⇒ m p = + e e ¯ ν ¯ ν L ∆=( = . Neither calculation matches observations. e 48 ν , . ) ) e e ¯ ν ν = 0 − T T e high enough. Kinetic equilibrium: e 2 2 ,L / / + ,Y ∆ p n/p − → = 200 (1+∆ (1 n e e s = 3 MeV ¯ ν ν + T T e e ¯ ν e e ν ¯ ν ν T L L = ≃ e ν e e T ¯ ν ν λ λ = p n In both calculations, initial Additionally, it is difficult to keep
Sensitivity to supernova conditions 1 rically symmetric star with a “mountain” Lattimer, AST 301, Supernova/Neutron Star Lecture – p.19/3 ropole moments, such as ties of gravitational waves etime which propagates as a these waves. Gravitational t it has been indirectly shown to modes of neutron stars − Hz g 11 10 − 7 − 20 10 − 10 c Binary star systems Rapidly rotating non-axisymmetric stars, such as aOscillating neutron asymmetric stars, such as Collapsing and exploding stars to the extentThe the Big are Bang not sphe Amplitudes of at most Frequencies in the range Velocity of Waves are polarized
Gravitational Radiation • • • • • • • • • wave. Gravitational radiation is theradiation energy can transported be by produced by sources with time-varying quad A gravitational wave is a fluctuation in the curvature of spac Gravitational radiation has not been directly detected, ye exist by the decay ofare binary neutron star orbits. Some proper 1 observed from a ] 1 φ ⊙ 2 P kin, Lattimer, AST 301, Supernova/Neutron Star Lecture – p.20/3 E − decaying Keplerian orbits. ) 5 ] r . φ . c v 2 /π − = 0 . t 2 1 − ): =Ω /r × Ω ) M M 1 h ν r 7 2 − and r > c/ t ≈ 2 ) π/ ) cos[2Ω( 2 θ = M 2 θ + π 1 P 2 sin[2Ω( 5 M a ( θ 2 2 Hz ⊙ = L 4 M 6 . 2 2 1 − cos 0 (1 + cos / 17 . 1 M 2 2 10 0 · 4 neutron stars in a binary with separation of R M M |≃ 5 ) 9 ≃ 1 1 a a G . 2 ⊙ hr 2 πc | M M 32 M 2 4 ≃ 3 + 2 2 , erg/s 4 4 ν 1 a = c c G G 22 32 M r r 1 1 − ( s, dt dE 10 G 10 · − − · − 5 . 2
Example: Binary Star With Circular Orbit 7000 = = 6 = ≃ ≃ |≃ × + h The observed frequency of gravitational waves is Wave amplitudes (for observes at distances To a good approximation, components ofOrbital binaries frequency: will follow Ω = Power radiated: L h h The intensity of gravitational waves decreases as An observer in the orbital plane has | Consider two 1.4 M L distance of 1 kpc: P 1 ) e ( f 3 / 1 « 2 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.21/3 M ⊙ + M 1 decays due to gravitational M „ PSR 1913+16 2 ⊙ M M 1 ⊙ M M 3 / 2 5 / 7 « − ⊙ ´ 2 P s. e πP . 6 2 3 − . − / ) „ , 1 5 5 10 A . π Myr. − · ´ ` (8 . 4 5 / e = 0 192 AP 3 / e − = 0 96 37 9255 8 . = 122 e 3 P + s / 5 2 = 4 = ≡ − s e 15 = 3 3 6 ˙ 73 24 10 P ˙ /c − · P ⊙ 9 10
Decay of Binary Orbits . 1+ · dP/ M ` 6 0 G P . = 3 R ≡ ≡ c ) t = = 4 e ⊙ ( c this timescale is reduced by about a factor of 5. For an eccentricity of so For our previous example, A Time to coalescence is t f P For a circular orbit, For a binary with arbitrary eccentricity, the binary period radiation emission as 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.22/3
Mergers involving Neutron Stars Must Occur 1 o 001 001 . . ◦ 0 0 2 . ± ± 77 Coles et al. (2004) 333 345 . . Lattimer, AST 301, Supernova/Neutron Star Lecture – p.23/3 4); f: Bogdanov et al. (2002) 00020002 1 1 . . ◦ 0 0 2 . ± ± 47 4414 3867 . . ◦ 6 005005 1 1 . . . 0 0 0 ± ± ± 85 245 2250 2.932.45 6.38 7.75 7.62 10.1 0.088 0.617 0.274 9 a,b,c d e,f . 337 250 87 . . 1 1 PSR 0707-3039 PSR 1913+16 PSR 1534+12
Comparison of Binary Pulsars ) ) The shortest orbital period binarieseccentricities. have non-zero Mean pulsar velocities (300-400 km/s)receive imply large neutron kicks stars at birth. Kicks enhance supernova survival probabilitypost-supernova and orbital shrink separations if directed opposite t supernova's motion. ⊙ ⊙ (s) • • • (M (h) (M yr) (M i e a: Lyne et al. (2004); b: Solution 1, Jenet & Ransom (2004); c: A B P a/c d: Weisberg & Taylor (2002, 2004); e: Stairs et al. (2002, 200 GW M M T References 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.24/3 Rosswog & Price, Science, 2006
Neutron Star Merger 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.25/3 Bloom et al., Nature, 2005
Short Gamma Ray Burst elliptical galaxy supernova Short duration No afterglow Occurs in No coincident 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.26/3
Lethal Effects of Nearby Supernovae 1. Optical and UV light 2. X-rays from explosion 3. X-rays from supernova remnant 4. Gamma rays 5. Neutrinos 6. Cosmic rays 1 as protection by Lattimer, AST 301, Supernova/Neutron Star Lecture – p.27/3 tures. It is generally ision) ed in Effects . Nothing detectable erg/g = 1 4 Q 10 Eventual death in nearly all cases Vomiting, diarrhea, appetite loss, listlessness Temporary and slight decrease is white blood cell count Nausea, vomiting, longer-term decrease in white cell count Q Above plus hemorrhaging and eventual death in some cases . We will assume × 1 ≤ Q Short-Term Radiation Effects Lethality of High-Energy Radiation ≤ is a quality factor which accounts for various factors, such 1 . 0–25 clothing, body orientation, internal body organs and struc 0 gray = 1 joule per kilogram = rad = 0.01 gray = 100 erg/g rem = 1 rad Q 25 – 100 100 – 200 200 – 300 300 – 600 above 600 • • • Dosage (REM) Exposure and absorption of high-energy radiation is measur Long-term safe limit is 5 rem/yr (US Nuclear Regulatory Comm 1 is in pc, D 2 . s / . 2 s Lattimer, AST 301, Supernova/Neutron Star Lecture – p.28/3 . / s cm pc. If the flux persists for a / /s) / is the distance. If 2 rem D erg rem will generate a flux at Earth = 1 2 Q 2 D 994 D D ) D × 2 8280 = 40 cm = 6000 cm = Q πD × area 2 (4 mass ) 000 , L/ D × 6000 18 50 10 42 × erg/s at distance × 10 2 Flux = 1 . 42 D 8280 (3 π width = 150 cm 4 = 10 × L Dose = SN flux Dose = Flux = height
Calculating Doses is the luminosity in X-rays and gamma-rays and L A lethal dose is accumulated in 0.6 s from a SN at The dose is The average body mass is about 50 kg (110 lbs) = 50,000 g. month, a lethal dose is received from a SN up to 2.1 kpc away. Assume a human in space,The unshielded cross-sectional by area Earth’s of atmosphere. a human is about where . The flux of radiation from a supernova is (units are erg/cm a supernova of luminosity 1 Al), 26 10 per billion illion out of 50 lt yr, ased on SN ormation ( and volcanic otopes that nearby , SN 1054 (Crab), f communities, ir greater total X-ray xposure to solar and Lattimer, AST 301, Supernova/Neutron Star Lecture – p.29/3 are converted into nitrogen 3 and O 2 Fe). 60 pc, time between events is estimated to be about 100,000 yrs. 200 D < as well as more recently ( 1987A, an underluminous SN II. Radiation is particularly harmful toalthough phytoplankton some and water ree shielding is available. Estimates set an ozone-destroying SN II at closer than 8 pc,Rates b of SN within 10 pc in solar neighborhood vary200 from million 0.05 years). - Sun is nowFor entering the galactic disc. Nearby SN include Vela (800300,000 lt yrs yr, 12,000 ago), yrs RX ago), J0852.0-4622 Geminga (660There (5 ly is yr, abundant 900 evidence yrs from ago). short-livedsupernovae have radioactive occurred, is both prior to the solar system’s f years, mostly occuring when Sun is passing through disc (10 m
Effects on the Planet • • • • • • energy. Type Ia supernova are potentially more deadly because of the Gamma-rays can induce reactions in which N Nitrates have been found in ice cores coinciding with SN 1006 and a SN 1060-1080 oreruptions X-ray are burster. also (The detected 11-year from solar 1000-1100.) cycle oxides, depleting the ozone layercosmic which radiation. increases surface e • • • 1 Lattimer, AST 301, Supernova/Neutron Star Lecture – p.30/3 Motizuki et al., Nature, 2009 University of Alaska Geophysical Institute solar cycle
Ice Core Samples and SN 1 limb down from s of parsecs stars. esulting in deforestation, s formed in the absence Lattimer, AST 301, Supernova/Neutron Star Lecture – p.31/3 Al was already homogeneously distributed. 26 Fe tells us about the environment where the 60 Ni found in dust on the ocean floor 15,750 feet 60 Ni ratios in primitive meteorites are lower than samples Fe which must have been injected a million or so years 58 Al and 60 26 Ni/ 60 Fe, halflife 1.5 million years. 60 Sun formed: in a dense stellar cluster with numerous massive trees and walk upright. below sea level in the Pacific Ocean. of distant from dust enriched in occurred about the same time and may have forced hominids to c Evidence exists that The implication is that the oldest solar system planetismal Younger objects had live This decoupling of live There is other evidence for a SN 2.8 million years ago a few ten A shift in the African climate toward more arid conditions, r after solar system formation, when from Earth, Mars and the chondrite parent bodies.
and Supernovae Near the Sun • • • • • • 60
Fe