Neutron Stars & Black Holes (Chapter 11) APOD Student Learning Objective Indentify properties of Neutron Stars & Black Holes NASA What is a neutron star? A Neutron Star is a collapsed core remnant. High Mass Star Core Mass Limit: < 3 M sun Radii: km Neutron Core SN explosions leave core remnants that collapse more than a White Dwarf Electrons and protons combine into neutrons Degenerate neutron pressure stops the collapse Neutron Core Remnant Neutron Star RCW 103 2,000 year-old-remnant 10,000 light years from Earth Neutron star near center rotates once every 6.7 hours Image Credit: Chandra Neutron Stars Hot Spin Rapidly Super High Density Strong Magnetic Field A neutron star the size of a sugar cube would weigh 100 million tons on Earth! Neutron stars in binary systems emit x-rays. High Energy Object = High Energy Photons (x-rays) Practice 1)What causes the neutron star to be very hot? 2)Why does a neutron star spin rapidly? 3)What makes the magnetic field of a neutron star particularly strong? 4)Is a neutron star a star? How are neutron stars found? Pulses of x-rays are seen if the electron beams sweep across our path. (Pulsars) X-rays pulse on and off. Periods = 8.51 seconds Crab Pulsar OnCrab Pulsar Off Practice 1)Why is not possible for a pulsar to be a pulsating star? 2)Do you think Neutron stars spin rates change? 3)Can a Neutron star become a Nova? 4)What you expect to find near, associated with, a neutron star? Supernova Remnant & Neutron Star APOD The Pulsar Powered Crab APOD What is a black hole? A Black Hole is a collapsed core remnant. Highest Mass Star Core Black Holes Degenerate pressure cannot balance the weight of the core Core collapses to a singularity Gravity is concentrated Light is trapped According to special relativity, nothing can travel faster than light. If light cannot escape a black hole, then nothing can! V esc (Earth) = 11 km/s V esc (Sun) = 600 km/s V esc (Black Hole) = 3 x 10 8 m/s Approaching a Black Hole Traveler perceives "normal" time and length. Observer perceives time slowing down & length contracting. Event Horizon Matter that crosses the event horizon cannot escape. The Scharzchild Radius is determined by mass. Our Sun Current Radius696,000 km Scharzschild Radius3 km X-Rays Indicate Star Ripped Up by Black Hole APOD Practice 1)Which type of Supernova may produce a black hole? 2)Would it be infinitely dark or infinitely bright if you were able to cross the event horizon? Why? Black Holes emit x-rays and affect stellar motions. Stellar motions are erratic Accretion disk emits x-rays Turbulence Gas Heats Emits x-rays Cygnus X-1 1 st Black Hole observed 7 M sun 1/4 size of Earth Black hole evidence in the center of our galaxy Evidence suggests that a ULX in the galaxy NGC 5408 has a black hole with about 2,000 solar masses NASA The rotation of a black hole drags space-time around with it. (ergo-sphere) Matter ripped apart Ejected matter takes black hole energy Rotation of Space Time Practice If our Sun became a black hole, what would happen to the orbits of the planets? Would the planets be sucked into the black hole? Explain. Are Wormholes Real? Wormholes In 1935, Albert Einstein and Nathan Rosen realized that general relativity allows the existence of bridges, originally called Einstein-Rosen bridges. A wormhole is a connection between two extreme curvatures of space. Calculations indicate a wormhole could be maintained using Negative Energy.