Extreme Stars Our Sun is more massive than about what percentage of stars? How many orders of magnitude less metals does the record holder, HE 1327-2326, have than the Sun? 3. What is the temperature of the coolest white dwarf found so far? In what constellation can you find Polaris? The spectral type of Polaris A, B, and C all have the letter … How far above the horizon is Polaris, as seen from Atlanta?

Extreme Stars Our Sun is more massive than about what percentage of stars? 90% How many orders of magnitude less metals does the record holder, HE 1327-2326, have than the Sun? 1/250,000 = 5 orders of magnitude 3. What is the temperature of the coolest white dwarf found so far? 4300 K, cooling for 8-9 Gyr In what constellation can you find Polaris? Ursa Minor The spectral type of Polaris A, B, and C all have the letter … F B. How far above the horizon is Polaris, as seen from Atlanta? 33.5 ± 1 degrees

Neutron Stars Progenitor single: one massive (> 8 Msun) star with Fe core double: one star + white dwarf … mass slurping Process 1. p+ and e– crushed together into n and neutrinos 2. BOUNCE = SN EXPLOSION 3. shock wave blows star apart 4. neutron degeneracy pressure stabilizes core shock wave not centered so some of central core survives bounce

Neutron Stars

Neutron Stars Progenitor single: one massive (> 8 Msun) star with Fe core double: one star + white dwarf … mass slurping Process 1. p+ and e– crushed together into n and neutrinos 2. BOUNCE = SN EXPLOSION 3. shock wave blows star apart 4. neutron degeneracy pressure stabilizes core Observe radio pulses … pulsar for millions of years regularity … ROTATION narrowness … SMALL OBJECT Notes not really a “star” 1.4 Msun … 20 km in diameter intense magnetic fields … not all neutron stars are pulsars shock wave not centered so some of central core survives bounce

Neutron Stars Chandra picture + Hubble picture

Millisecond Pulsar

Black Holes Progenitor single: one massive (> 20 Msun) star with Fe core double: one star + neutron star … mass slurping Process 1. core more than 3 Msun 2. neutrons can’t hold against gravity! 3. matter “crushed” into no size 4. gravity so intense, not even light can escape … Observe nothing (directly) … in binary systems X-ray source … ENERGETIC large star tossed … MASSIVE gas flowing … BINARY no object seen … DARK variability … TINY shock wave not centered so some of central core survives bounce

Cygnus X-1

Black Holes Notes black holes ARE NOT vacuum cleaners black holes ARE heaters and eaters Special nothing goes faster than light Relativity

Special Relativity

Black Holes Notes black holes ARE NOT vacuum cleaners black holes ARE heaters and eaters Special nothing goes faster than light Relativity General light is affected by gravity

General Relativity General Relativity

Light Affected by Gravity?! photon signals from spacecraft may have tortured trajectories

Black Holes General light is affected by gravity Relativity photons use energy to dig their way out of black hole  redshift as we see them  photon frequency as clock ticks … time dilation

Schwarzchild Radius PE = KE GMBHmph/R = (1/2)mphv2 R = 2GMBH/c2 imagine a photon at the “event horizon” --- same as the “Schwarzchild radius” PE = KE GMBHmph/R = (1/2)mphv2 of course, v = c R = 2GMBH/c2 (this is the classical derivation, but the relativistic derivation yields the same result) Sun ~ 3 km Earth ~ 9 mm

Black Holes

Cluster Evolution “banana peel”

Open Clusters Examples Pleiades and Hyades in Taurus Characteristics 1. in Milky Way 2. loose aggregate 3. few hundred stars 4. young … less than 500 million yrs 5. massive stars still present 6. gas and dust 7. heavy metals

Hyades use IC2391 ???

Globular Cluster M80

Globular Clusters Examples M13 in Hercules, Omega Centauri Characteristics 1. outside of Milky Way 2. tight ball 3. few hundred THOUSAND stars 4. old … more than 10 billion yrs 5. G, K, M stars, red giants, white dwarfs present 6. no gas and dust 7. few metals

Globular Cluster: Mult Main Seq Bedin et al. 2004  Centauri with HST observe: double main sequence multiple turnoffs multiple subgiant branches deduce: different He content? two star formation epochs? star cluster/tidal tail behind?

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Calculate the densities in grams/cubic centimeter (g/cm3) of Densities of the Stars Calculate the densities in grams/cubic centimeter (g/cm3) of A. our Sun today 1.0 Msun 1.0 Rsun B. Sirius 2.0 Msun 2.0 Rsun C. Proxima Centauri 0.1 Msun 0.1 Rsun D. Betelgeuse (red supergiant) 15.0 Msun 650.0 Rsun E. future Sun (white dwarf) 0.5 Msun 0.01 Rsun