Those from fe catastrophe are type ii supernova

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Unformatted text preview: e II supernova EE8086 EE8086 – Astronomy: Stars, Galaxies & Cosmology All supernovae shine brilliantly 10b Suns. Supernova type distinguished by their light. white dwarf supernovae lack H lines & fade steadily with time star type fade in 2 distinct stages massive Page 15 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 16 Distance Measurement with White Dwarf Supernova White dwarf supernovae always occur when the 1.4 Msun dwarf supernovae always occur when the limit is reached same maximum luminosities. good distance indicators di more luminous than Cepheid variable stars can measure out to greater distances measure out to greater distances Yet Distance of the white dwarf supernova (& its galaxy) determined using the inverse square law. = A ball of neutrons created by the collapse of the iron core in massive star supernovae. in a massive star supernovae. Typically No mass limit for massive star supernovae. Knowing luminosity of one white dwarf supernova luminosity of all are known. Apparent Apparent brightness Neutron Star 10 Km in radius more massive than the Sun more massive than the Sun Neutron stars are very dense. 1.5Msun with diameter of 10~20 km 1012 g/cm3 paper clip of this clip of this density outweigh Mount Everest luminosity 4d 2 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 17 Neutron Stars EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 18 Pulsars In a neutron star, it is neutrons rather than electrons that are closely packed. that are closely packed. Neutron degeneracy pressure stops collapse of core with mass < 3Msun . ith mass 3M Pressure arises when neutrons are closely packed Supports the core against crush of gravity Light Curve of Jocelyn Bell’s Pulsar Graduate student Jocelyn Bell & her advisor discovered a radio source in the Cygnus constellation in 1967. Rotate very rapidly with period very rapidly with period of 0.03~4 s. sharp pulse recurring every 1.33 s 300 pc (978 light years) away Magnetic fields are 10t times stronger than Earth’s. EE8086 EE8086 – Astronomy: Stars, Galaxies & Cosmology They called it a pulsar (Pulsating radio source). called it pulsar (Pulsating radio source) Page 19 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 20 Pulsar Pulsar in Crab Nebula Pulsars are Neutron Stars! A pulsar is a spining neutron star that beams radiation along its magnetic axis. Pulses came at very precise intervals. other massive object can spin so fast (< 1s-1 for white dwarf) Radio emission concentrated at magnetic poles magnetic field trillion times of Earth’s no man-made? Mystery solved by late 1968 when a pulsar was discovered in the heart of Crab Nebula. Beam of radiation sweeps of radiation sweeps round & round when poles are not aligned with rotation are not aligned with rotation axis. Crab pulsar pulses in visual light. EE8086 – Astronomy: Stars, Galaxies & Cosmology see a pulse of light each see pulse of light each time the beam sweeps past Earth Page 21 Lighthouse of the Galaxy EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 22 Rotation Periods of Neutron Stars Youngest pulsars have the shortest periods. Geometry determines whether we see a puls...
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This document was uploaded on 11/25/2013.

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