ASTR 1040 Accel Astro: Stars & Galaxies Today Binary mass transfer Joys of nearest supernova: SN 1987A How mass transfer from binary companion can spin-up pulsar White dwarf supernovae from mass transfer in binary system, but also repeated novae Remarkable white-dwarf supernovae (binaries) Prof. Juri Toomre TA: Nicholas Nelson Lecture 17 Tues 8 Mar 2011 zeus.colorado.edu/astr1040-toomre toomre Logistics Evening Review on Thur 7-99 pm for Second Mid- Term Exam on Mon Mar 14 Review Sheet #2 and new Homework Set # 8 available. HW # 7 due today Observatory Night # 5 tonight, 7pm+. Overview read S.3 Spacetime & Gravity Read Chap 19 Our Galaxy with care Remember: Planet Finder homework due next Thur Mar 17 (prior SB) Pulsars and Neutron Stars Pulsars are lighthouses in our Galaxy! REMINDER Fast electrons in strong magnetic fields neutron stars, black holes Synchrotron Radiation Different shape from thermal radiation: emits at all wavelengths, strongest in radio Thermal light from stars visible and IR Visible vs. X-ray X emission Synchrotron light from neutron stars X-ray and radio Visible light X-ray light 1
Visible Light vs. Radio Thermal vs. Synchrotron Back to famous friend! SN: Crab Nebula M1 Elliptical galaxy -- visible Same galaxy -- radio 4 July 1054 Crab s s pulse patterns x-ray visible Crab Nebula SNR infrared radio optical x-ray radio Crab SNR composite Oct 06: Spitzer (IR), Chandra (X), Hubble (V) Chandra X-ray view of Crab center 2
Crab pulsar at work: Nov 00 Apr 01 Gradual slowing down of pulsar rotation Energy emitted in pulses comes from rotational kinetic energy Chandra X-rayX HST Visible REVISIT Listening to Pulsars PSR B0329+54 typical, normal pulsar: : period 0.714 sec (~1.40 rotations/sec) PSR B0933-45 VELA pulsar: period 89 millisec (0.089 sec) (~11 rot/sec) in SNR ~10,000 yrs ago PSR B0531+21 CRAB pulsar: ~30~ rot/sec youngest known PSR J0437-4715 4715 millisec pulsar, ~174~ rot/sec PSR B1937+21 fastest pulsar, ~642~ rot/sec surface of star moving at 1/7 c! Clicker review red giants The main source of energy for a star as it grows in size to become a red giant is. B. A. gravitational contraction B. hydrogen fusion in a shell around core C. helium fusion in the core D. hydrogen fusion in the core Story of SN 1987A in LMC 24 Feb 1987: SN in LMC (160,000 ly away) Large Magellanic Cloud (LMC) (10,000 tiles with Spitzer composite IR) BEFORE AFTER (SN 1987A) 3
Mysterious triple rings in SN 1987A Supernova SN 1987A 20 year birthday picture (Chandra + HST) SN 1987A: Brightening knots 1994 > 2006 Making a millisecond pulsars spin it up! Mass transfer onto neutron star in binary system can spin up the pulsar even to 1000 times per second (ms) Accretion disk forms: extremely hot ( X-ray Burster if He fusion) Black Widow millisecond pulsar evaporating companion star in cocoon has spun it up Sketch SNR numbers game Cygnus Loop Chandra X-ray X Image 4
Cassiopeia A: SN in ~1680 (Flamsteed( Flamsteed) Cass A: Viewed with Spitzer IR Youngest SNR in MW (Chandra X-ray image) synchrotron emission Neutron star at center Kepler s SNR (1604) L 10 6 Stellar graveyard is very much alive! Chandra X-ray image red: oxygen yellow: iron blue: shock prompt Type Ia SN Mass transfer in binaries adds jazz white dwarfs, neutron stars or black holes -- all can play! 10-4 40,000 Temperature 3,000 Compact Companions in Binary Systems Mass transfer from red giant companion spirals onto accretion disk Inner parts become VERY hot -- glow in UV, X-raysX Stages in mass exchange in binary system Here consider two massive stars -- clock runs fast 5
Mass transfer accretion disk disk gets very hot -- radiates brightly makes neutron stars and black holes visible! White Dwarfs in Binary Systems Again, mass transfer from red giant companion spirals onto an accretion disk But too much mass can take white dwarf over the edge! REMINDER WD snooze pyrotechnics (in in three flavors) 1 or 2: binary mass transfer flash fusion on WD 1. 2. Accretion of gas onto white dwarf can lead to H fusion on surface Star becomes much brighter nova (may blow off shell) NOVA NOVA Nova Cygni 1992+2 Recurring Nova T Pyxidis ~ every 20 yrs White Dwarf SUPERNOVA 3: If exceed 1.4 M SUN Collapse of WD, explosive fusion burning of carbon star all gone! Brightest SN: superb beacons for measuring distances 6
SUPERNOVA Light Curves Bright Candles in Sky to Measure Distance (Type II core collapse) (Type Ia -- WD) SUPERNOVAE in Other Galaxies Bright enough to be seen as sudden, bright point in other galaxies Many astronomers monitor nearby galaxies nightly to catch them 1 per 100 years per galaxy means that if you monitor 100 galaxies, see ~ 1 SN per year) If monitor a million galaxies, likely to find 30+ new ones each night! Next: Overview read S.3 Black Holes plus courtesy of Albert Einstein s s (1911) General Theory of Relativity: gravity is really the warping of spacetime around an object with much mass Light travels in straight lines and its bending comes from spacetime being curved by gravity S.3 Spacetime & Gravity 7